Engineering a Quieter America - Institute of Noise Control Engineering

Transcription

Engineering a Quieter America:
Progress on Consumer and Industrial
Product Noise Reduction
A TQA workshop aand
nd International INCE symposium
sponsored by
The INCE Foundation and the Noise Control Foundation
organized by
The INCE Foundation
hosted by
The National Academy of Engineering, Washington, DC
Tamar Nordenberg
Nordenberg, Rapporteur
Adnan Akay,, Robert D. Hellweg, William W. Lang,
George C. Maling, Jr
Jr. and Eric W. Wood, Editors
Institute of Noise Control Engineering of the USA
Progress on Consumer and Industrial
Product Noise Reduction
A TQA workshop and International INCE symposium
sponsored by
The INCE Foundation and the Noise Control Foundation
organized by
The INCE Foundation
hosted by
The National Academy of Engineering, Washington, DC
This report has been approved by the Board of Directors of
INCE/USA for publication as a public information document. The
content, opinions, findings, conclusions, and recommendations
expressed in the report do not purport to present the views of
INCE/USA, its members, or its staff.
Generous support for this project was provided by
the International Institute of Noise Control Engineering,
the INCE Foundation, and
the Noise Control Foundation
Copyright © 2016, Institute of Noise Control Engineering of the USA, Inc.
All rights reserved
ISBN: 978-0-9899431-3-0
Library of Congress Control Number: 2016939856
Printed in the United States of America
This report is posted on the INCE/USA website, www.inceusa.org
ii
ORGANIZATIONS Advancing Noise Control Engineering
The International Institute of Noise Control Engineering (I-INCE) is an international,
nonprofit, nongovernmental consortium of more than 40 member organizations with interests in
the control of noise and vibrations that produce noise. I-INCE was chartered in Zürich in 1974
on the basis of Swiss Civil Law. The objectives of I-INCE are to sponsor annual international
congresses on noise control engineering in the INTER-NOISE series as well as other specialized
conferences, and to promote cooperation in research on the application of engineering principles
for the control of noise and vibrations. I-INCE undertakes technical initiatives and produces
reports on important issues of international concern within the I-INCE field of interest.
The Institute of Noise Control Engineering of the USA (INCE/USA) is a nonprofit,
professional-membership organization incorporated in 1971 in Washington, DC. A primary
purpose of the Institute is to promote engineering solutions to noise problems. INCE/USA is a
Member Society of the International Institute of Noise Control Engineering (I-INCE).
INCE/USA has two publications, the Noise Control Engineering Journal (NCEJ) and Noise
News International (NNI). NCEJ contains refereed articles on all aspects of noise control
engineering. NNI contains news on noise control activities around the world, along with general
articles on noise issues and policies.
The Institute of Noise Control Engineering Foundation (INCE Foundation) is a nonprofit,
tax-exempt, publicly supported, charitable organization established in 1993 and incorporated in
New York as a Section 501(c)(3) organization. The purposes of the Foundation are to support,
promote, and advance scientific and educational activities directed toward the theory and
practice of noise control engineering and to promote and support such scientific and educational
activities through grants, funding, and financial assistance to various individuals, institutions,
and organizations.
The Noise Control Foundation (NCF) was established in 1975 to provide administrative
services to the newly formed INCE/USA. It is a nonprofit, tax-exempt organization incorporated
in New York as a Section 501(c)(3) organization. At the end of the century when administrative
support for INCE/USA was transferred to a commercial organization, NCF was re-chartered to
be devoted to the development of national and international policies related to the technological
aspects of noise control engineering.
iii
WORKSHOP STEERING COMMITTEE
ADNAN AKAY
Provost, Bilkent University in Ankara, Turkey
Lord Professor and Head Emeritus
Mechanical Engineering Department
Carnegie Mellon University
ROBERT D. HELLWEG, JR.
Hellweg Acoustics
Past President, Institute of Noise Control Engineering of the USA
WILLIAM W. LANG, NAE
President, Noise Control Foundation
GEORGE C. MALING, JR., NAE,
Managing Director Emeritus,
ERIC J.W. WOOD
Former Director, Noise and Vibration Group,
Acentech Incorporated
President, INCE Foundation
iv
Technology for a Quieter America
Advisory Board
George C. Maling, Jr.
Managing Director, Emeritus
Institute of Noise Control Engineering
of the USA
Member, NAE
Tony Embleton
Retired Head, Acoustics and Mechanical
Standards
National Research Council of Canada
Foreign Associate, NAE
James E. Barger
Chief Scientist
Raytheon BBN Technologies
Member, NAE
William W. Lang
President
Noise Control Foundation
Member, NAE
Leo L. Beranek
President Emeritus
American Academy of Arts and Sciences
Member, NAE
Richard H. Lyon
Chairman
RH Lyon Corp
Member, NAE
David T. Blackstock
Professor Emeritus of Mechanical Engineering
University of Texas at Austin
Member, NAE
Eric J.W. Wood
Former Director, Noise and Vibration Group,
President, INCE Foundation
Ira Dyer
Professor Emeritus of Ocean Engineering
Massachusetts Institute of Technology
Member, NAE
v
PREFACE
The Technology for a Quieter America, (TQA) report was published by the National Academies
Press in October 2010 following a five-year study by the National Academy of Engineering (NAE)
of the environmental noise situation in the United States. The report includes findings and
recommendations for government, industry, and public actions that may mitigate or eliminate those
noise sources that pose a threat to public health and welfare.
In 2011 the Institute of Noise Control Engineering (INCE) Foundation and the Noise
Control Foundation established a TQA Follow-up Program to identify specific noise topics and
to develop relevant recommendations aimed at improving the noise climate in the United States.
The TQA Follow-up Program consists of a series of events involving experts in selected TQA
topic areas to further assess specific noise issues and publish a series of recommended
remediation measures.
This report presents the results of one TQA Follow-up event, a workshop titled
Engineering a Quieter America: Progress on Consumer and Industrial Product Noise Reduction,
which was organized and/or sponsored by the INCE Foundation, the Noise Control Foundation,
INCE/USA, and International INCE. The workshop was hosted by the NAE at the National
Academies Keck Center, Washington, DC, on October 6 and 7, 2015.
The workshop and this report address the contributions of noise control engineers to
improving both quality of life and the U.S. economy by providing domestic manufacturers with
the expertise to develop, produce, and sell the quieter products now demanded by global
markets. Expected future noise control engineering technologies are also addressed.
Thirty-one persons attended the workshop, with presenters representing manufacturers,
consultants, trade and standards associations, universities, and a widely known consumer
publication. Many attendees had 30 to 40 years of direct engineering experience in consumer athome products or industrial products.
The workshop addressed consumer products ranging from automobiles to yard-care leaf
blowers, and industrial products ranging from air-moving devices to valves. Products ranged
from small hand-held devices to million-pound off-road trucks.
Appendix A provides the agenda for the workshop. Participants and their affiliations are
identified in Appendix B. Appendix C provides a list of acronyms, abbreviations, and units in
this report.
vi
ACKNOWLEDGMENTS
This report has been reviewed in draft form by members of the Technology for a Quieter
America (TQA) Advisory Board, all of whom are noted for their technical expertise in noise
control engineering and acoustics. Many of the Advisory Board members contributed to the
preparation of the TQA report published by the National Academies Press in October 2010. They
now represent the continuing dedication of Academy members to a quieter America through the
TQA Follow-up initiative. This is an excellent example of the National Academy of
Engineering’s (NAE’s) commitment to the social value of engineering.
The rapporteur, Tamar Nordenberg, was assisted in the preparation of this report by a
technical editing team consisting of Robert Hellweg, George Maling, Adnan Akay, William
Lang, and Eric Wood, whose efforts before, during, and following the roundtable have been
invaluable.
The Steering Committee members are grateful to the 30 people who attended the
workshop and are identified in Appendix B. Twenty-five people made technical presentations
addressing their areas of technical expertise during the two-day workshop.
The following 29 organizations were represented during the workshop:
ABB Inc.
AGS Consulting LLC
AHRI
AMCA International
ASHRAE
Association of Home Appliance Mfgs
Bilkent University
Consumer Reports
CSTI Acoustics
Cummins, Inc.
ECHO Inc.
Hellweg Acoustics
Hoover & Keith, Inc.
Hudson Valley Acoustics
INCE Foundation
I-INCE
INCE/USA
Ingersoll-Rand
InSinkErator
Intel Corporation
JKT Enterprises
National Academy of Engineering
Office of Naval Research
Owens Corning
RSG
SSA Acoustics, LLP
The Ohio State University
Thanks also to the staff of the NAE, which hosted the roundtable. Proctor Reid, Program
Director, and his assistant Jason Williams made the roundtable possible through their supportive
efforts to ensure that the event ran smoothly. The Committee also thanks NAE President Dan
Mote who contributed opening remarks on the importance of noise control engineering.
Finally, thanks to the NAE’s Committee on Technology for a Quieter America, chaired
by George Maling, that produced the TQA report with its numerous findings and
recommendations.
vii
viii
CONTENTS
EXECUTIVE SUMMARY
1
1.
INTRODUCTION
3
2.
CONSUMER PRODUCTS AT HOME
2.1 The Sound of Appliances
2.2 Evaluation of Consumer Product Noise
2.3 Sound Quality and Engineering Noise Control of Various Consumer Products
2.4 Trends in Appliance Noise Control
2.5 Kitchen Sink Food Waste Disposers
2.6 Quieter Leaf Blowers
2.7 Information Technology Equipment
2.8 PNR. A Simplified Product Noise Rating for the General Public
2.9 Automobile Interior Noise
5
5
9
13
18
23
26
34
39
44
3.
COMMERCIAL AND INDUSTRIAL PRODUCTS
3.1 The Need for Quieter Machinery in Industrial Facilities
3.2 Air-conditioning, Heating, and Refrigeration Institute Standards and their
Contributions to the Engineering of Quieter Products
3.3 The Contributions of ASHRAE TC2.6 in the Engineering of Quieter Products
and Progress in Noise Reduction for Heating, Ventilating, Air-conditioning and
Refrigeration Systems
3.4 Large Industrial Air Movement Devices
3.5 Industrial Power Generation Equipment
3.6 Advanced Noise Control Technology for Electrical Power Generator Sets
3.7 Industrial Motor Noise Control: History, Costs, and Benefits
3.8 Compressor Noise
3.9 Power and Distribution Transformer Noise
3.10 Engineering Quieter Valves and Piping Systems
3.11 Noise from Gear Drives
3.12 Engineering Quieter Off-road Machines
3.13 Mining Noise Sources and their Control
3.14 Natural Gas Pipelines: Noise from Compressor Stations and Other Sources
3.15 Noise Control Engineering for Military Noise Sources
3.16 National and International Noise Emission Standards for Consumer and
Industrial Products
51
51
54
ix
59
65
74
79
85
91
97
102
107
112
118
123
128
134
4
INSTITUTES OF NOISE CONTROL ENGINEERING
4.1 International Institute of Noise Control Engineering
4.2 Institute of Noise Control Engineering of the United States of America
141
141
143
5.
OBSERVATIONS
145
APPENDICES
A. Workshop Agenda
B. Workshop Attendees
C. Acronyms, Abbreviations, and Units
A-1
B-1
C-1
x
EXECUTIVE SUMMARY
This report documents two dozen noise control success stories during the past few decades.
These were presented at a workshop attended by experienced engineers working at U.S.
manufacturers producing consumer products ranging from automobiles to yard-care leaf blowers,
and industrial products ranging from air-moving devices to valves. Products ranged from small
hand-held devices to million-pound off-road trucks. The report addresses ongoing contributions
by noise control engineers to improving both quality of life and the U.S. economy by providing
domestic manufacturers with the expertise to develop, produce, and sell the quieter products now
demanded by global markets. Expected future noise control engineering technologies are also
addressed.
The 2015 workshop was titled Engineering a Quieter America: Progress on Consumer
and Industrial Product Noise Reduction. It was held on October 6-7, 2015, at the Keck Center of
the National Academies in Washington, DC. Thirty-one people attended the workshop, and 25
technical presentations were made on a wide variety of associated topics. Adnan Akay, Eric
Wood, Robert Hellweg, and George Maling served as co-chairs of the workshop, and these four
along with William Lang made up the organizing committee. NAE President Dan Mote and
NAE Program Director Proctor Reid provided opening remarks.
Noise from consumer products was the subject of the first seven papers presented. Wayne
Morris from the Association of Home Appliance Manufacturers (AHAM) said that the
Association has adopted a series of standards produced by the International Electrotechnical
Commission (IEC) for the rating of home appliances. These standards, known as the IEC 60704
Series, cover a wide variety of home appliances and provide a consistent method of measuring
the noise produced. When in use by all manufacturers, they will provide a uniform way for
consumers to include consideration of noise emission when selecting products. Another
organization that connects with the public is Consumer Reports (CR), which has collected a
database of product noise levels that probably ranks among the largest in the world. CR's Mark
Connelly presented their test methods for rating noise.
The next presentations addressed how noise control engineering is applied to a wide
variety of consumer products, from dishwashers to food waste disposers to leaf blowers to
information technology equipment. Significant progress has been made over the last two decades
in the production of quiet products, and consumer demand for quiet products is high. Matthew
Nobile of Hudson Valley Acoustics presented a method of rating product noise that closely
resembles IEC methods used in the appliance industry, and removes the confusion associated
with noise emission ratings based on sound pressure and sound power.
One paper was presented on progress made in the reduction of automobile interior noise.
Quiet automobile interiors are highly prized by consumers, and great progress has been made in
identifying how noise enters the cabin and how it can be reduced.
The next presentations addressed the workshop's second theme: commercial and
industrial products. Robert Putnam discussed the need for quiet products in industry. Then, two
presenters—representing the Air Heating and Refrigeration Institute and Ingersoll Rand, and the
American Society of Heating, Refrigerating and Air-Conditioning Engineers —addressed the
1
considerable progress made in the air-moving industry. Next, Geoff Sheard, the chair of the
board of the Air Moving and Conditioning Association, discussed his industry's progress
including the use of computational techniques to design low-noise fan blades. Low-noise designs
are needed as we move into the construction of high-performance buildings and green buildings.
One finding in the Technology for a Quieter America report was that “There is wide
dissatisfaction with noise in buildings in which business is conducted. Post-occupancy
evaluations by the Center for the Built Environment at the University of California at Berkeley
(2007) have shown that occupants are generally dissatisfied with noise and sound privacy.”
Indications are that green buildings can be even worse.
Ten presentations were then devoted to progress in reducing noise from industrial products
and components. Topics included:










Industrial power generation equipment
Electric power generator sets
Industrial motors
Compressors
Transformers
Valves and piping
Gears
Off-road machines
Mining equipment
Natural gas pipelines.
Many of these products can be thought of as a system along the lines of the classic
source-path-receiver model. But the current system model must include multiple sources,
multiple paths, and in many cases multiple receivers. Multiple sources include all of the
components listed above.
Presenters consistently mentioned various drivers for noise control. While, in the context
of consumer products, customer demand for quiet products and information on product noise is
widespread, sources of demand for quiet commercial and industrial products include community
requirements, community pressure, customer requirements, and government requirements.
There was little discussion about community requirements. Local noise ordinances are
known to be inconsistent and in some cases out of date.
Community pressure can be felt in many ways. For example, a company installing power
transformers may be aware of a surrounding community's concerns about unacceptable noise,
and may establish specifications that a transformer manufacturer must meet. Direct customer
demand may arise when a builder of a system such as a power plant places noise requirements on
the components that make up the system. Finally, there may be government requirements;
examples are European noise requirements on construction equipment and, in the United States,
FERC noise requirements on gas compressor stations and large LNG compressor facilities.
Two additional papers were presented. Kurt Yankaskas presented noise control work by
the U.S. Navy, and Robert Hellweg summarized national and international noise standards.
2
1
INTRODUCTION
Background
The report Technology for a Quieter America emphasizes the importance of engineering to the
quality of life in America, and in particular the role of noise control technology in making a
quieter environment possible. Subjects addressed include environmental noise in communities;
control of hazardous noise in workplaces; metrics for assessing noise and noise exposure; noise
control technologies; standards and regulations for product noise emissions; cost-benefit analysis
for noise controls; the roles of government, education and public information in noise control;
and a wide range of related recommendations. Implementation of the recommendations in the
report will result in reduction of the noise levels to which Americans are exposed and will
improve the ability of American industry to compete in world markets where increasing attention
is being paid to products' noise emissions.
Scope
This report on a TQA Follow-up workshop provides information on the progress made by noise
control engineers in recent decades—specifically, in noise reductions of consumer products
inside and outside the home, and industrial products for international and domestic markets.
Projections are included on further noise technologies anticipated in the future.
Content
Approximately one-third of the 25 workshop presentations summarized in this report addressed
engineering noise control progress during recent decades for consumer products such as
appliances, yard-care equipment, and automobiles.
The second portion of the workshop presentations summarized here addressed a wide
range of commercial and industrial products including gen sets, motors, compressors, electric
transformers, valves, gears, off-road mobile machines, mining equipment, and natural gas
pipelines, as well as military equipment and noise standards.
This report includes a summary of findings based on the workshop presentations. The
workshop agenda and a list of the 30 workshop attendees are provided as appendices.
A professional court reporter was retained to produce a transcript for both days of the
workshop. Presenters were provided the opportunity to review and edit their portions of the
transcript. A professional science writer was retained to attend the workshop and prepare draft
presentation summaries based on the transcript and the slides displayed at the workshop. The
presenters were then provided the opportunity to review and edit the draft summaries of their
presentations. Occasionally, presenters inserted post-workshop information for purposes of
clarification and/or addition of insights. The TQA Editorial Committee reviewed and edited the
presentation summaries to ensure clarity after which they prepared this report.
It is expected that there will be continuing dialogue among workshop participants and
interested parties and future TQA Follow-up workshops are expected during 2016 and beyond.
3
4
2
CONSUMER PRODUCTS AT HOME
2.1 THE SOUND OF APPLIANCES
Wayne Morris - Association of Home Appliance Manufacturers
Sound quality is among the primary areas of focus for the Association of Home Appliance
Manufacturers (AHAM). As it promotes the development of ever-quieter appliances, AHAM is
mindful of factors such as the non-traditional set-up of many modern homes and consumers'
subjective experiences and expectations.
Wayne Morris spoke about noise reduction in the home appliance arena from his perspective as
vice president for technical operations and standards at the Association of Home Appliance
Manufacturers. AHAM is the trade association that represents appliance manufacturers around
the world that market their products in the U.S. and Canada.
Morris introduced his association as an American National Standards Institute (ANSI)
accredited standards developer. The association also writes test performance material standards
and methodology standards for judging home appliance performance, and participates in
developing—and harmonizing—external standards in the U.S. and other countries that relate to
performance as well as safety and sustainability.
Morris spoke about the changing home environment, with appliances used in different
ways today than in previous times. “Great rooms,” kitchens, laundry rooms, bathrooms and
bedrooms house different appliances than they once did.
In keeping with this type of evolution in the ways people live, AHAM focuses on sound
quality issues in the context of the consumer's subjective experience. Beyond the traditional
measurement approaches—such as sound pressure at 1 meter away—many companies are also
using sound jury rooms to incorporate the consumer perspective. Especially in cities, apartments
can be 400 or 500 square feet (35 or 45 square meters), Morris pointed out, and people are
spending more time inside. Under these circumstances, the speaker said, “We find that the sound
quality becomes increasingly important to them.”
Companies are examining sound throughout the cycle of a product such as a dishwasher
or clothes washer so they can make the sound more “pleasant” for the consumer, the presenter
explained. Meanwhile, AHAM—and its technical committee in particular—continually works to
improve industry standards such as the ISO 3740 series and IEC 60704 series. Figure 2.1-1 lists
the primary ISO and IEC standards that apply to appliances generally and to specific types of
products.
The quality of appliance sounds has “improved drastically,” Morris said, and appliances
are quieter than ever. It's “like the asymptotic curve,” he said. “You'll never get to perfect, but
you'll get closer, and that's the journey we're on to find a way to improve the sound quality for
the consumer.”
5
Sound pressure does not suffice as the sole way of describing sound to the consumer, he
said. And the marketplace is responding to consumer demands for additional information and
products that emit subjectively more acceptable sounds.
As an example of investigation in this area, Morris discussed the 2015 paper titled
“Sound Preference Development in Correlation to Service Incident Rate,” by authors including
Terry Hardesty. Figure 2.1-2 identifies the paper more completely. As the paper discusses, the Aweighted sound power provides an incomplete picture of sound, and consumer perception is
difficult to quantify. The paper addresses the fact that appliances are found in new areas of the
home, and that “connected home appliances” are being used that are integrated with each other.
For example, appliances today can be turned on and off depending on factors such as the
demand-side management of a power generation system. The consumer can choose the
automatic activation and de-activation of an appliance from within the home or by the utility.
This approach presents its own challenges, Morris said, as an appliance can make noise at
inconvenient times.
The aesthetic appeal of appliances today goes far beyond the products' fit and finishes to
include factors such as sound quality. Consumers have wide-ranging objections, and some
actually complain if a product is too quiet, making it difficult to tell whether it is running. “I
would take that as a compliment in a way because the sound quality people in our companies
have done an exceedingly good job,” Morris said, but consumers can view it negatively.
Challenges representing, in the speaker's words, “a good test of engineering skills”
include optimizing sound quality when the millions of U.S. homes are so different from each
other in terms of their size, shape, type of walls, interior surface quality, and other characteristics
that affect sound. Jury testing can help predict consumer sound preferences by taking into
account people's overall impressions of sound quality based on factors such as amplitude,
tonality, modulation, and roughness. This type of additional understanding of what consumers
find to be favorable and unfavorable in terms of sound can help companies improve their
products.
Morris spoke next about helpful sound-related technologies developed over the last 25
years or so. Substantial improvements have been made in components such as motors; fans,
including cooling fans; and insulation materials. At the same time, industry is also focusing on
advances in energy efficiency, sustainability, and safety.
Industry benefits from, and responds to, input from consumers and consumer
publications, Morris said. The speaker also acknowledged the work of acoustical engineering
consultants in improving the products of many of AHAM's member companies—especially
small and medium ones that cannot afford a full-time acoustical engineer on their staff.
In response to a question about making information about sound quality and associated
metrics accessible to consumers and engineers, Morris stated that companies often view their
sound quality approaches and technologies as proprietary.
6
Noise levels of household appliances
•
Noise emitted from an household appliance is typically defined as
noise level at 1m from the appliance.
•
Standards for measuring noise levels
• IEC 60704-1
• ISO 3741
•
Modes of operation for noise measurement
• Full cycle (Example – Wash cycle of a dishwasher)
• Segment of a cycle (Example – Spin mode of a washer)
Other standards for Appliance Sound Quality
Determination of sound power levels and sound energy levels of noise
sources using sound pressure
• ISO 3741—Precision methods for reverberation test rooms
• ISO 3743-1 Engineering methods for small moveable sources
in reverberant fields—Comparison method for hard-walled
room
• ISO 3743-2 Engineering methods for small moveable sources
in reverberant fields—Methods for special reverberant test
rooms
• ISO 3744 Engineering method in an essentially free field over
a reflecting plane
• ISO 3745 Precision methods for anaechoic rooms and hemianaechoic rooms
Figure 2.1-1 Applicable industry standards.
7
Other IEC documents
•
•
•
•
•
•
•
•
•
•
•
•
IEC 60704-1 General requirements
IEC 60704-2-1 Test methods for vacuum cleaners
IEC 60704-2-3 Test methods for dishwashers
IEC 60704-2-4 Test methods for clothes washers and spin extractors
IEC 60704-2-6 Test methods for tumble dryers
IEC 60704-2-7 Test methods for fans
IEC 60704-2-10 Test methods for cooking appliances
IEC 60704-2-11 Test methods for food preparation appliances
IEC 60704-2-13 Test methods for range hoods
IEC 60704-2-14 Test methods for refrigerators
IEC 60704-2-15 Test methods for food waste disposers
IEC 60704-3 Procedure for determining and verifying declared noise
emission values
Figure 2.1-1(continued) Applicable industry standards.
Examples
• Paper “Sound Preference Development and Correlation
to Service Incident Rate.” Terry Hardesty, Sub-Zero;
Gabriella Cerrato, Todd Freeman, Eric Frank, Sound
Answers.
• Presented 10 August at the Inter-Noise conference in
San Francisco and on 21 August at the International
Congress of Refrigeration in Yokohama.
• Available from the International Institute of Refrigeration
and the Institute of Noise Control Engineering of the
USA.
Figure 2.1-2 “Sound Preference Development” article.
8
2.2 EVALUATION OF CONSUMER PRODUCT NOISE
Mark Connelly - Consumer Reports
Consumer Reports (CR) is a nonprofit organization that evaluates product noise, among many
other factors, to inform consumers' purchasing decisions. Consumers yearn for quieter products,
the organization has found and, as CR data reflects, in some cases manufacturers have made
strides in light of this preference.
Mark Connelly, senior director of product testing at Consumer Reports, spoke based on his 27
years of experience with Consumer Reports magazine. In its labs, CR tests more than 3,000
products annually, and noise is one of the most important properties the organization evaluates.
“We try to take a holistic approach to a product and say which is the best product for you, the
consumer,” stated Connelly, a supervisory mechanical engineer in CR's Yonkers, N.Y., labs.
Connelly introduced CR as a nonprofit organization founded in 1936 to “work for a fair,
just and safe marketplace for all consumers and to empower consumers to protect themselves.”
Consumer Reports has about 4 million magazine subscribers and 3.5 million website subscribers,
and accepts no advertisements or corporate donations.
When evaluating noise, CR generally tests for sound pressure and sound quality. Products
tested for noise include lawn mowers, tractors, chainsaws, leaf blowers, power washers, snow
throwers, washers, dryers, dishwashers, refrigerators, vacuum cleaners, and many more. (For
audio products, such as headphones, TVs, and cell phones, the product's audio property is also
evaluated.)
CR uses a sound level meter to measure A-weighted sound pressure levels, listening and
aiming for consistency across product categories. Reference models are used to ensure year-toyear consistency, as well—for example, a product considered excellent for noise and one
considered poor. The organization conducts sound testing primarily for audio products in its own
anechoic chamber, as shown in Figure 2.2-1, and also uses a group of sensory panelists to
evaluate sound. (Noise-emitting products are tested in conditions simulating actual usage.)
Figure 2.2-2 exemplifies how CR presents noise data to consumers. A product essentially
earns an A, B, C, D, or F rating but behind that there are gradations on its performance. “Just like
a student could receive an A and get a 100, a student could also get an A and get a 90,” Connelly
explained. An A translates into an excellent red circle, and an F gets a black circle. The goal is to
allow consumers to understand a complicated topic at a glance. For some products, noise
information is also presented in a narrative format, with concise summaries that can run a page
or two in length.
Connelly next discussed in more detail how CR tests products for noise performance,
starting with the example of lawn mowers. Sound readings are taken using a Brüel & Kjær
(B&K) sound level meter in the center of a large field. Testers take pains to achieve consistency
in such factors as the position from which readings are taken and product configurations (cutting
height, for example, in the case of lawn mowers).
Noise is evaluated in various ways to predict the experience of not only the operator, but
also others such as a neighbor living next door. Best practices are followed in all cases to achieve
consistency and avoid arbitrary results. “We have to be very consistent,” Connelly stressed,
9
“because when the manufacturers come to discuss our results with us, we need to tell them, ‘This
is what we did.’”
Moving next to the example of vacuum cleaners, Connelly explained that CR experts test
noise levels with two samples of each vacuum model, using a sound level meter positioned
where a person's ear tends to be during vacuuming. Consistency is achieved in factors such as
noise meter placement, rug height, clean bags or bins, and vacuum operation. CR's
measurements differ in some respects from the industry's methods to better represent the
consumer's experience, as the CR microphone location is near the ears of the operator, the
speaker explained.
Connelly gave a historical perspective on what has changed over the last 15 years in
terms of product noise. Figure 2.2-3 shows data on noise from dishwashers and refrigerators
during this time frame, revealing that while little change has been seen in these products on the
noisier side of the spectrum, significant improvement is seen in a then-and-now comparison of
the quieter models. For example, the minimum dishwasher noise has dropped from about 53
dB(A) to 39 dB(A). Today, the presenter pointed out, “You almost have to put your ear to some
dishwashers to determine if they are running.” Meanwhile, little reduction has been seen in the
acoustic or noise properties of outdoor power equipment.
The presenter also touched on the subject of consumer psychology, and the possibility
that consumers think a quiet product (a quieter lawn mower, for example) may be a less powerful
one.
Consumers want to know, basically, “Is this product quieter than that product?” What CR
aims to do with its data is level the playing field, in a market filled with noise claims such as
“library quiet.”
On the topic of European products and any contrasts with American ones, the presenter
said European manufacturers have been effective at lowering dishwasher noise levels. Following
the introduction of the first Bosch dishwashers, other manufacturers have followed the
company's lead. Today, various manufacturers offer quiet dishwashers, while noisier versions are
also still being marketed.
Noise is very much on consumers' minds, according to CR surveys. In one survey, 13
percent of washing machine owners ranked the noise of washing machines as their most
important concern—even above how well they wash clothes or how energy efficient they are.
The subject of noise represents an opportunity for manufacturers and retailers to
differentiate themselves, the speaker concluded, while noise at the same time can represent an
annoyance—and even a safety issue—for consumers.
Responding to a question, Connelly stated that CR has changed over the decades from a
very insular organization to a “proactive” one that wants to engage with manufacturers. “We are
happy to have manufacturers come in and ask us about our test protocols, our test procedures,
and the data that we got with their product,” he said, adding that CR hopes to engage with the
engineering community on noise issues.
Another question went to whether consumers are willing to pay more for a quieter
product. Yes, Connelly responded, some consumers consider lower noise to be a priority for their
dishwasher, for example, and are willing to pay a premium for the quieter model.
10
Figure 2.2-1 Consumers Reports' anechoic chamber.
How we present noise data
1
1
Figure 2.2-2 CR's simple format for presenting noise data.
11
Historical perspective: the last 15 years
- indoors -
• Dishwashers:
• Then: Max 63 dBA; minimum 53 dBA
• Now: Max 63 dBA; minimum 39 dBA
1
1
• Refrigerators:
• Then: Max 52 dBA; minimum 40 dBA
• Now: Max 52 dBA; minimum 31 dBA
Figure 2.2-3 Dishwasher noise, 15 years ago and today.
12
2.3 SOUND QUALITY AND ENGINEERING NOISE CONTROL
OF VARIOUS CONSUMER PRODUCTS
David Bowen - Acentech Incorporated
Carefully considered noise control engineering methods can prove invaluable in consumer
product design. During development, accounting for consumer perceptions—not just objective
metrics—is key to creating a winning product.
David Bowen, with acoustical consulting firm Acentech Incorporated, shared his expertise in the
area of consumer product noise. His knowledge is based on more than 25 years working with the
gamut of consumer and medical products such as those listed in Figure 2.3-1. Bowen opened
with some general impressions:



Many products actually seem to be getting louder, largely driven by the desire for more
powerful products that are lower in cost and lighter in weight.
More products are placed in living areas—washing machines on homes' main floors and
air purifiers in bedrooms, for example.
Expectations are changing. For instance, the desire is for a robotic vacuum cleaner that
can clean the floor without noise to distract a homeowner trying to focus on another task.
In noise control engineering, “noise audits” are a useful way to identify and quantify the
sources of excitation, the path, and the radiation mechanisms. Figure 2.3-2 sums up the
methodology based on this noise audit concept. Identifying the sources requires the isolation of
each sound source, which can sometimes be accomplished by covering up the entire product—
with lead sheet, for example—and then exposing a single source, or by relying on appropriate
forms of signal processing.
Having identified the component sounds, ranking them based on their contributions to
total noise allows priorities to be set for sound reduction. This method, Bowen said, “enables you
to find an effective path for noise reduction engineering.”
Quiet product design is a cost-effective means for decreasing noise. The design analyses
can be supported by noise audit results from earlier models or competitor products. In the course
of designing a product to decrease noise, performance is sometimes also bolstered.
Next, the presenter discussed an Acentech project to produce a quieter electric
toothbrush, illustrated in Figures 2.3-3. Acentech identified noise emanating from the handle as
the main source, even more than the brush and motor. By vibration isolation of the toothbrush
gear drive from the handle, overall noise was decreased by approximately 7 dB(A).
Bowen next turned to foreign regulations as a driving force behind some noise reduction
projects. His example: One client retained Acentech to reduce its vacuum cleaners' overall noise
by 10 dB(A) to meet a European directive effective in 2016. Because companies may not want to
manufacture two different product models, the U.S. can benefit from foreign requirements
though this country is generally reluctant to impose its own noise limits.
Bowen next discussed sound quality, and how the ear/brain system shapes people's
subjective response to sounds and to the objects producing them. Sound quality depends on a
person's response, not a purely objective metric, and people's subjective responses depend on
their expectations based on the product's function and the context of its use. Perceptions matter
13
because, for example, a quiet vacuum cleaner may be suspected of poorer cleaning performance.
One major attribute considered in the context of user perceptions is “acceptability” of the
sound. Factors affecting acceptability include strength and magnitude; annoyance value
(bothersome aspects of sound such as roughness and sharpness); amenity value (pleasing aspects
of sound such as regularity and harmonicity); and information content (related to the product
performing properly).
Bowen next addressed the related subject of the importance of using listening panels that
represent a cross-section of consumers and are not biased by an association with the
manufacturer. These panels' preferences can guide product design goals and directions. To
improve sound from a user perspective, these panel members are sometimes asked to weigh in on
sounds from virtual products made up by altering sounds of components and mixing them
together. From this type of study, experts can build a quadratic regression model, and beyond
this, use principal component analysis to help form custom sound quality metrics that can
correlate well with the jury ratings for use in future analyses. The approach's ultimate goal is a
response surface contour that elucidates the path to a better design.
Among other examples of noise-reducing redesign, Bowen returned to the example of a
vacuum cleaner, as summarized in Figure 2.3-4. He discussed the process of isolating the
product's sounds and mixing them together in various steps for presentation to a jury. According
to regression equations plotted in contour plots, the strongest contributors to the perceptions of
acceptability and perceived power were the motor and airflow sound, and a higher level of
rotating brush noise could increase perceived power without decreasing acceptability. By this
step and further increasing acceptability by essentially redesigning the motor, Acentech achieved
a 5 to 10 dB(A) reduction in broadband motor vibration level and a 6 dB(A) reduction in noise
level.
Bowen's team has also examined the question of how much consumers would pay for
better sound. In the case of a tractor priced at about $23,000, a jury heard pairs of tractor sounds
and was asked, “What is the largest price difference you would be willing to pay for the tractor
sound that you prefer?” On average, the highest price difference jurors were willing to pay was
about $600 for, in this case, a cab over the tractor. In another study, this time on blenders priced
around $150, jurors indicated they would be willing to pay, on average, about 50 percent more
for a “quiet version.”
In conclusion, Bowen stated that while some consumer products are being designed to
perform more quietly, the tendency seems to be for consumer products to instead become louder
due to marketplace pressures for products that are lighter, smaller, and more powerful; this
tendency also applies to new or significantly improved products. Bowen qualified this by stating
“All those factors contribute to increased noise, or at least as consultants, those are the ones that
we hear about, the problem ones.” From the manufacturers' perspective, while they understand
the importance of sound quality to consumers, they still may not be prepared to invest in a fullblown sound quality study.
14
Some Consumer Products Worked On
(Noise “audits”, noise reduction, and/or SQ improvement)
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Blenders / food processors
Vacuum cleaners & other floor-care products
Dishwashers
Refrigerators
Fast-cook ovens, gas ranges
Washing machines
Hairdryers
Electric toothbrushes
Flat-panel TVs
Motorized shades
Air Purifiers / Fans / Humidifiers / Fragrance dispersers
Air conditioners / Dehumidifiers
Air mattress pumps
Garage door openers
Shop compressors
Mosquito control device
Power tools, lawn & garden equipment, furnaces
Medical products (many, but not necessarily “consumer products”...)
2
Figure 2.3-1 Consumer product examples.
Engineering Noise Control Methodology
based on the “Noise Audit” Concept
• Find and quantify the sources of excitation,
the path, and radiation mechanisms.
• Rank-order based on contribution to total noise:
– Depends on source strength, path (structural
response), and radiation efficiency.
– Provides a basis for developing noise reduction
approaches, starting with the “loudest” source.
– Establishes an effective path to reduce noise without
“spinning one’s wheels” on sources that don’t matter.
4
Figure 2.3-2 Conducting a noise audit.
15
Noise Audit Example: Powered Toothbrushes
50
Average Reverberant Room Noise Level - A Weighted
SteadyOperation - No Load on Brush
Noise Level dB re 20 uPas
40
30
20
10
0
16 Hz Bandwidth
-10
100
1000
Frequency
10000
Hz
Unit C
Baseline A-weighted narrowband
spectrum of
noise from typical unit
Figure 4b Braun 3-D Excel - Narrowband Spectrum
6
Powered Toothbrush Noise Audit
60
Average Reverberant Room Noise Level - A W eighted
Steady
Operation - No Load on Brush
Noise Level dB re 20 uPas
50
40
30
20
10
Motor Noise
0
100 160 250 400 630 1000 1600 2500 4000 6300 10000
125 200 315 500 800 1250 2000 3150 5000 8000 12500
Frequency
7
Original Condition
Figure 14
Hz
Brush Noise
Handle Noise
Braun 3-D Excel - Brush and Handle Noise
Powered Toothbrush: 7 dB reduction
(via isolation of gear drive head from handle)
Electronic Toothbrush Noise
Reverberant Room Measurements
70
Noise Level dBA re 20 uPas
Average Noise Level in Reverberant Room
Steady
Operation - A W eighted Level
60
50
40
30
20
10
100 160 250 400 630 1000 1600 2500 4000 6300 10000
125 200 315 500 800 1250 2000 3150 5000 8000 12500
Frequency
8
Hz
Original Condition - 62.0 dBA Isolated Drive Head - 55.3 dBA
Figure 2.3-3 Creating a quieter electric toothbrush.
16
Vacuum Cleaner SQ Example
Main Sources of Noise
16
Example Component Sounds
for a Vacuum Cleaner SQ Study
BASELINE VACUUM CLEANER SOUND
17
Vacuum Cleaners
(Example jury test regression results - upright unit)
Acceptability = 35.7 - 1.2M - 1.4A
- 0.2B - 0.06M2 - 0.03A2 - 0.06MS
+ 0.05MA - 0.06MB.
Perceived Power = 42.3 + 0.88M
+ 1.06A + 0.45B + 0.06M2 +
0.054B2 - 0.08MA - 0.06AB.
Where M, S, A, and B stand for
changes in the sound levels in dB
for Motor, Suction fan tones,
Airflow, and rotating Brush noise.
18
Figure 2.3-4 Identifying ways to improve vaccum cleaner’s “sound quality.”
17
2.4 Trends in Appliance Noise Control
Kevin Herreman - Acoustic Research Center, Owens Corning
Over the years—and in keeping with the changing ways people enjoy their homes—appliances
such as dishwashers and clothes washer-dryers have become progressively quieter. With the
increasing attention paid to appliance sound levels, this feature has achieved recognition as an
important element of brand identity.
Kevin Herreman, who works in Owens Corning's acoustic research center, spoke about trends in
noise control in various appliances. His company provides materials used in reducing noise in
appliances, and its research center is accredited as a third-party testing laboratory and provides
testing for appliance manufacturers. So the company, he said, has a “finger on the pulse of what's
happening in the appliance world.”
An appliance must do what it is designed to do, of course, Herreman said, and must also
operate independently—the owner starts the appliance, and it does its job. Now, appliances are
also expected to do their jobs quietly.
The speaker spoke briefly about the history of home appliances, as summarized in Figure
2.4-1. By the 1980s, homes were beginning to be designed with appliances in mind. By the
1990s, open floor plans were in fashion so noise in the kitchen was often traveling to nearby
spaces. Laundry rooms started to move from the basement to the main space near the kitchen or
upstairs near the bedrooms.
With more discretionary income for many in the 1990s, consumers' interest in quiet
appliances grew. And in that decade, homeowners desired quieter units to replace the
unacceptably loud ones that had been disrupting their lives. Appliances differentiated themselves
based on sound and costs rose with this feature. In the 2000s, sound levels were an integral part
of manufacturers' brand strategy, Herreman explained.
Meanwhile, over the decades, competition dwindled as the number of major
manufacturers decreased from at least 20 in the U.S. during the 1970s to five in the 1990s and
three today. With a small group of manufacturers making many brands, differentiation among
brands has become crucial, and quiet—and “ultra-quiet”—has taken a place among the products'
distinguishing features.
Dryers started receiving noise control packages. As for refrigerators, Herreman referred
to them as the “Steady Eddie” in noise control for many years. Noise did start creeping up for a
time as other appliances in the same area were typically much louder, but refrigerators won
attention back for noise control in the 2000s as other appliance sound levels dropped.
Herreman returned to the topic of brand segmentation, showing published sound levels
for today's dishwashers, in Figure 2.4-2. Commodity-level appliances are the relatively
inexpensive and loud units. Value brands are a step up and more expensive. And premium
brands are the quietest and most costly. Manufacturers often gain in profits and brand
recognition by marketing brands across price ranges.
Examining trends in sound levels and the associated prices for the consumer, Herreman
found substantial drops from 2012 to 2015 in the average dollar increase in sale price per dB
lower. He looked at a 50 dB(A) dishwasher, which was the quietest in 2004, and a 39 dB(A) unit,
the quietest in 2012. Putting those together and looking at pricing, Herreman found: “It was $905
for the 50 dB(A) unit in 2012” and “in 2015, it's $608”—a 30 percent decrease in the sale price
18
for the unit. “This is something that I did not expect,” he said. Looking next at the 39 dB(A) unit,
it cost $2,000 in 2012, down to about $1,400 in 2015. The average dollar per dB in 2012 was
$106—that is, for every decibel quieter the price increased by $106. By 2015, a decibel quieter
fetches a much lower $72. It is expected that either the consumer’s expectation of the availability
of quieter products devalued quieter products at the same level or, as is more likely, the
manufacturers reduced the sound levels of lower cost units to increase their competitive position
in the market.
There is a constant pressure for quieter products, Herreman explained. In the early 2000s,
with consumers wanting a sense of what products are quieter than others, the INCE/USA
technical committee on product noise emissions began developing a consumer product noise
rating. And in 2004, Owens Corning developed an easy-to-understand noise rating for Sears to
convey to prospective buyers how loud or quiet each product was. To this day, Sears uses a
simple noise level rating system based on A-weighted sound power level for appliances, as
shown in Figure 2.4-3, to allow consumers to compare dishwasher noise. Initially based on the
IEC 60704 standard, the system has been adapted for North America by using AHAM
specifications.
As a result of noise ratings, Herreman said, the quietest dishwashers are getting quieter—
decreasing in a single recent year from 39 dB(A) in 2012 to 37 dB(A) in 2013. Trends are
graphed in Figure 2.4-4. The quietest units are sold today for about $2,000, Herreman noted.
Speaking about the range of new, quieter models, the presenter pointed out that some
dishwashers in 2004/2005 were approaching 70 dB(A), and the loudest units currently being
introduced are 55 dB(A). The quietest dishwasher available on the market today is 13 dB quieter
than in 2005 (37 dB(A) vs 50 dB(A)), and the loudest is 8 dB quieter. Dishwashers are
approaching refrigerator sound levels of 38 to 45 dB(A), Herreman stated. “Unit model mixes
are becoming much, much quieter,” Herreman said, “and I believe all of this is due to the
labeling and giving consumers a simplified method just to tell the difference.” One reason to go
to a standardized labeling system, the speaker emphasized, is that different measures, such as
sound power levels and sound pressure levels, are both shown in dB(A), which can confuse the
consumer.
Returning to other types of appliances, Herreman mentioned that sound is decreasing for
laundry appliances, thanks in part to sound packages on a wide range of dryers; convection ovens
are receiving sound-reducing material in their designs; premium range hoods are marketed for
their quiet advantage; and food waste disposals, blenders, and food processors are additional
examples of products now being sold with lower sound levels.
These noise reductions are being accomplished thanks to improved technologies,
including use of multiple small motors. Companies are “identifying the right motor for the right
job, instead of trying to use one brute force motor to do everything.”
Also, new materials such as improved isolation materials are being designed into
products to optimize their performance. And gears are being machined for better fits and
finishes. “You're seeing a combination of acoustic parts with thermal parts,” Herreman said. “So
now you're reducing costs and improving efficiencies and reducing sound levels at the same
time.” Also, cycle modifications that reduce sound levels are being undertaken to improve
efficiency.
Looking to the future, Herreman foresees several trends:

Increased multi-family homes will drive noise levels down further
19

More hard surfaces will be used in homes, and as concrete is increasingly used in
construction, the resulting increase in inside sound will have to be compensated for with
reduced appliance noise.
Herreman hopes that labeling will increase “so that people can make choices which will
allow the market to determine noise levels that are available.”
Background
• In 50s-60s-70s
– Appliances became part of daily life
– New appliances being developed to ease life
• In the 80s
– Appliances becoming typical part of life
http://www.vintageadbrowser.com/household-ads
• Hookups standard in new homes
– Dishwashers included increasingly in new homes
• Noise begins to become a purchase driver
• In the 90s
– Homes get loud with open floor plans
– Laundry moves upstairs
– Economic prosperity allows increased discretionary
spending
October 6, 2015
NAE Workshop
Kevin Herreman
Background
• In the 00s
–
–
–
–
–
Sound Levels used in manufacturer brand strategy
Dishwasher sound is rated by Sears™
Laundry sound packages become more common
Refrigerators continue to leverage quiet
INCE Technical Committee on Product Noise Emission
begins to develop a consumer Product Noise Rating
http://sm7tog.com/the-vital-role-of-kitchen-appliances-in-the-trendy-kitchen/
October 6, 2015
http://www.nytimes.com/2011/01/02/realestate/02cov.html?_r=0
NAE Workshop
Kevin Herreman
Figure 2.4-1 Appliances and appliance noise over the decades.
20
Sound level is a brand strategy in appliances
• Premium units are quiet
– Manufacturers link lower
sound level to higher
quality
– Brand identified by the
range of sound levels.
– Provides greater profit
and more brand
recognition
2012 - Average of $106 per dB
2015 - Average of $72 per dB
October 6, 2015
NAE Workshop
Kevin Herreman
Figure 2.4-2 Quieter appliances as strategic advantage.
Case Study - Dishwasher
• In 2004 Sears® introduced a single number
dishwasher sound rating for units to be sold in
their stores
•
The standard to be used was based on existing IEC 60704 series of appliance standards
modified for the North American market
October 6, 2015
NAE Workshop
Kevin Herreman
Figure 2.4-3 Sears' simple rating system for dishwashers.
21
Effect of Noise Rating
• Quietest units get quieter
• Range of new models is
quieter
• Dishwasher in 2015 vs 2005
– Quietest is ~13 dB lower (37 dB)
– Loudest is ~8 dB lower ( 64 dB)
October 6, 2015
NAE Workshop
Kevin Herreman
Figure 2.4-4 Quieter appliances follow from noise ratings.
22
2.5 Kitchen Sink Food Waste Disposers
Cynthia Jara-Almonte - InSinkErator, Emerson Commercial & Residential Solutions
InSinkErator developed first-of-their-kind quieter food waste disposers, along with promotional
materials to answer the question, “Why should I pay more for this model?”
Cynthia Jara-Almonte, with InSinkErator, a division of Emerson Electric, presented information
about household food waste disposers (garbage disposals). Founded in 1938, InSinkErator is the
world's largest producer of these products, making all of their approximately 5 million units a
year in the U.S. The company, which supplies most major retailers, is highly vertically
integrated—winding its own motors and stamping, machining, and die casting, while outsourcing
such components as plastic, rubber, and fasteners.
Once seen as a convenience appliance, the food waste disposer is also recently
recognized as an environmentally friendly way to dispose of the average household's 2,000
pounds or so of annual food waste. InSinkErator's Evolution line is a premium product line
developed starting in 1999 and launched in 2006 with improved sound as well as improved
grind. Factors that spurred the development of this quieter product line, Jara-Almonte explained,
included the close proximity of kitchen and family rooms in many homes; and progressively
quieter other appliances such as dishwashers and refrigerators. Figure 2.5-1 describes the
evolution of the noise reduction program that she managed.
In trying to improve on noise performance, the company faced a lack of established
industry standards and test methodologies to objectively measure progress. (Jara-Almonte
pointed out that IEC 60704-2-15, which grew from the food waste disposer company's work with
the Association of Home Appliance Manufacturers (AHAM) to get standards for disposers, was
not implemented as an ISO publicly available specification (PAS) until 2008.) So in 1999, the
company set about defining its test procedures, including the grind medium to be used. And in
2000, the company built its first dedicated sound test facility, a hard surface test room, and
launched tests using B&K hardware and Pulse software for the tests.
The testing focused on the primary noise paths that the company identified with partner
Battelle. The challenge was blocking this noise while maintaining the product's functionality in
disposing of food waste. The sound-reducing components had to meet high-volume production
requirements (20,000 units a day); be cost effective; and meet agency requirements (UL;
American Society of Sanitary Engineering (ASSE); and AHAM).
To block noise coming through the throat of the sink, which the company identified as
the predominant source for noise, InSinkErator developed the “quiet collar sink baffle.” The part
keeps a little layer of water over the sink's opening which serves as a baffle to block noise.
To stop noise and vibration from transferring from the disposer to the sink and plumbing,
the company created a rubber anti-vibration sink mount. The component in the sink mount
supports the disposer, and was the company's first use of rubber as a structural material. Because
the rubber could be exposed to various chemicals that people poured down their sink,
InSinkErator teamed up with a domestic rubber company to design and develop rubber
components that would hold up.
As for the product's third path for noise—through the container body—the company
developed an engineered material, a multilayer composite material, placed around the grind
chamber. The materials differ slightly depending on the level of product. The company did not
23
seek to reduce source noise by quieting the grinding or the motor noise that is inherent in the
four-pole induction motor.
Effective sound reduction solutions developed and implemented by InSinkErator are
illustrated in Figure 2.5-2.
Internally, the company had used Zwicker loudness as its metric. For marketing, the
company developed a comparative percent-quieter measure to compare their lower-priced
Badger model and the premium Evolution line while grinding the same types of representative
foods. The next issue the company faced was how to market the new Evolution disposer, with its
significantly higher price point ($299, compared to the $79 Badger unit). “We had never sold
quiet before,” Jara-Almonte said. “We'd sold horsepower.”
To explain the price differential to customers—including end users and others such as
plumbers and retailers—InSinkErator developed videos and training materials. At the 2006
kickoff at the Kitchen and Bath Industry Show (KBIS) booth, the company had engineers to
explain the product, and offered sales kits showing the baffle, the rubber in the anti-vibration
mount, and other components. Figure 2.5-3 lists some of the marketing efforts associated with
the quieter kitchen sink food waste disposers.
Jara-Almonte concluded the presentation with an example of the promotional materials
InSinkErator uses. These include online videos that explain the upgraded parts in simple
language and offer recordings of the Evolution disposer's quieter grinding sound compared to the
lower-priced product. A link to the online video is available at:
http://www.insinkerator.com/en-us/Household-Products/GarbageDisposers/Evolution/Pages/Grind-More-Hear-Less.aspx]
Evolution family of FWD

Development of a new line of FWD began in 1999 and
product was launched in 2006
–


Objectives of new product were to be the quietest disposer
on the market and able to grind anything
Development spurred by increased emphasis on quiet
kitchen appliances
–
Appliance noise more noticeable in open concept or
integrated family rooms/kitchens
–
Other appliances (refrigerators, dishwashers) became quieter
Sound reduction portion started with a study to
identify dominant noise paths for grinding noise
–
44% air borne through throat
–
36 % structure borne
–
20% air borne under sink or unidentified
National Academy of Engineers Workshop Oct 2015
© 2015 – InSinkErator®
All Rights Reserved*
6
Figure 2.5-1 Evolution of the FWD noise reduction program.
24
Sound Reduction Solutions
Grinding noise
through
container body
•Added noise control
material around grind
chamber
•Different composition
materials for different
models
Presenter Name – Title – Date
Confidential & Proprietary – All Rights Reserved*
Structure Borne Vibration
transmitted through sink and
plumbing connections
8
Figure 2.5-2. Effective sound reduction solutions.
Marketing

Quantifying sound performance was a challenge
–
–
–
Without an industry standard, could not provide a “level” value on
packaging or in literature
Internally used Zwicker loudness as metric
Developed a comparative measure between Badger 5 and Evolution
units
• Expressed as percent quieter while grinding standard load (carrots,
celery, lettuce, and cooked steer rib bones)
• Excel– 60% quieter than a Badger 5

Developed videos, animations, advertising and training materials
to explain improvements in sound and grind
–
Comparative sound modules used in store displays
–
Engineers helped staff KBIS booth during product launch
Kits developed for sales force to help them explain the new
technology
–
National Academy of Engineers Workshop Oct 2015
All Rights Reserved*
11
Figure 2.5-3. Marketing quiet kitchen sink food waste disposers.
25
2.6 QUIETER LEAF BLOWERS
Larry Will - ECHO Inc. (retired)
ECHO Inc. has led the way in developing quiet leaf blowers, extensively redesigning several of
its models while keeping prices in check. The quiet options present a less drastic alternative to
bans for achieving community tranquility.
Larry Will, a former vice president of engineering for ECHO Inc. who is currently working for
the company as a contractor, spoke about the noise issue as it relates to leaf blowers. Will led the
company in developing the first quiet machine of its kind.
Will opened with the origin of leaf blowers, which evolved from a product called a
“duster mister” once used to spray pesticides and granular fertilizers, and in the 1970s was
informally adapted by landscapers to blow leaves by taking the tank off and replacing it with a
cover.
The product wasn't initially designed to be quiet, but rather to be effective for blowing
granular materials. At 6,000 RPM, with 10 blades, that translates into a 1,000 Hertz blade
passing frequency, Will pointed out. “In effect, you had a siren.”
Will called sound the “primary issue when it comes to leaf blowers.” In 1995, the loudest
leaf blowers tended to be 77 dB(A) at 50 feet, and ECHO reduced sound from its biggest
backpack blower at the time, to 65 dB(A), a 75 percent reduction in sound pressure. The
company also changed the impeller, trading in the product's square paddles for efficient ways of
pumping air. “We were able to quiet down the scream to the point where, in the case of a quiet
blower, it was virtually eliminated.”
In today's product line, ECHO has 13 blowers—five of them quiet blowers, shown in
Figure 2.6-1. Two are handhelds, one is a very small backpack, and two more are recently
introduced large units. Will next quantified the blower-associated sound. As for sound level, the
ECHO target threshold was and still is 65 dB(A) at 50 feet (15 meters) measured per the ANSI
Standard for leaf blowers. This industry test standard was written to measure sound outdoors as
would be experienced by a typical bystander, 50 feet away. Based on this complex standard, five
of ECHO’s blowers are 65 dB(A), four are 70 dB(A), two are 73 and two are 74. That’s an
average of 69 dB(A), which represents a significant reduction compared to what they were prior
to the start of ECHO’s sound attenuation project in 1995.
Under Will's leadership, on the original quiet blower, ECHO did away with the
frequencies and sound amplitudes that were deemed unacceptable. Following that, engineers
introduced completely new quiet designs while existing designs were sound reduced to whatever
point was economically possible. Noise attenuation highlights are shown in Figures 2.6-2a
through 2.6-2e.
The impeller blades were made irregular and tapered to eliminate the scream. An extra
part was added to the primary air intake port to the impeller, which tended to induce a laminar air
flow rather than a noisier turbulent flow.
The company also had to address exhaust noises. In response to pressure from the EPA to
drastically reduce exhaust emission, ECHO added a honeycomb-type catalyst inside the muffler
that also helped to attenuate sound. A cover was added around the cylinder cooling fins to direct
the noise, as well as the cooling air, to a side where it could be baffled. To prevent the rattling of
this metal part, it was uniquely formed and bent to make it rigid. Heat-resistant acoustic
26
materials were added to absorb high frequency sounds. Because the cooling fins were very thin,
various changes had to be made to reduce noises amplified by these fins due to cylinder
combustion-generated vibration.
Quiet units had enclosures added on all sides, including the front where the air enters into
the main impeller. A panel was placed on either side to prevent sound from emanating
horizontally. The plastic used is vibration resistant, made of a relatively soft material that does
not amplify vibration-generated noise. The air cleaner cover was modified to a two-piece design
that attenuates sound. Blower tubes and nozzles were modified to reduce sound produced by the
high-velocity and high-volume air flow, and an expansion chamber was added in one of the tube
sections with a sound-absorbing foam lining.
Next, Will addressed the question of whether sound attenuation causes people to perceive
ECHO’s products to be of higher quality. ECHO is well known for its high quality, Will said, but
quieter products come with a downside in this area: Landscapers sometimes equate noise with
power. “If it's quiet, they automatically assume it doesn't have the same performance as a noisy
unit,” said Will, who calls this phenomenon the “Harley-Davidson syndrome:” that is “If it
doesn't make enough noise, it isn't worth riding.”
The speaker then touched on price, showing Figure 2.6-3 with the price for each lownoise model. ECHO does not enjoy added profit from the quiet design. Its three smaller units
were designed quiet from the start, without any option for a noisy version. The larger ones,
which were designed as described earlier, were increased in price by $30, an amount equal to
ECHO 's cost for the upgrade. “We just passed that along, with no added profit margin.”
In terms of safety and health considerations, if a blower is 65 dB(A) or lower at 50 feet—
which is under 85 dB(A) at the operator’s ear—no ear protection is needed, the presenter said.
With a noisier model, sound protection is recommended in supplied literature.
The presenter also spoke about the concept of being a good acoustical neighbor. About
135 cities are trying to address leaf blower sound and some residents want all leaf blowers to be
banned. As a “good acoustical neighbor,” ECHO is the leader in providing quiet leaf blowers.
Even though it’s obvious to everyone that people appreciate a quiet neighborhood, landscape
contractors and homeowners generally don't care enough about noise reduction to spend the extra
money it costs to avoid being a contributor to the noise problem. Only a regulation requiring
quiet blowers will induce them to buy one. Buyers are primarily interested in performance and
low cost, but once they have experienced the quieter leaf blower and realize that it has all the
power they need, they often buy a second one. “Once they have one, I think they'll at least buy a
second one when the first one wears out,” the speaker predicted.
Most “anti-leaf blower advocates” want to ban the leaf blower because of noise, said the
presenter, but he mentioned that there are other factors that could help such as using the
equipment at a reasonable time of day rather than early morning when people are sleeping or in
the evening when many want peace and quiet. Historically, exhaust was a serious problem.
However, since 2005, exhaust emission has been significantly reduced. Along with hydrocarbons
in the atmosphere, dust is routinely brought up as an issue, he said. Leaf blowers are not intended
for use on unstable ground and ECHO says so in its literature. Properly used, no fugitive dust
will be generated, according to the speaker. Education rather than a ban is the only way to solve
these issues.
Will concluded with a discussion of his current professional task of contacting cities with
leaf blower issues—mostly on the East and West Coasts and a few in Canada—to inform them
about the availability of quieter products as an alternative to a ban. Among states, only Arizona
27
has taken any measures in the leaf blower context, passing a law setting out some requirements
for operator training and licensing. While the presenter does not oppose steps by cities toward
quieter products, he is against bans. “It's very difficult for the landscaper to do his job without
this tool,” he said. Also, he pointed out that bans don’t work. Most people will ignore a ban—
choosing to take a chance at paying a fine if necessary. For the homeowner, it is much easier and
quicker using a blower. For the contractor, a fine is less costly than using a broom and rake,
especially since the risk is low because the police are reluctant to issue citations against
otherwise law-abiding and hardworking landscapers.
In response to a question about selling only quiet leaf blowers—i.e., making all 13 units
in the product line quiet—Will said that, given the associated costs incurred and considering the
lack of consumer demand, those not presently designed to be 65 dB(A) would not be competitive
with other companies’ less expensive noisier products.
ECHO Has Five Low Noise Blowers
PB-250LN
PB-255LN
PB-760LNH
PB-265LN
PB-760LNT
Figure 2.6-1 ECHO's low-noise models.
28
What was done to the blower to reduce
sound levels?
* The fan and scroll was redesigned
sound levels?
* Muffler baffled, catalyst added
* Exhaust pipe redirected down
Figure 2.6-2a Quiet redesign highlights.
29
sound levels?
* The cylinder cooling fins modified
* Non amplifying enclosure added
* Acoustic foam is added
sound levels?
* Entire unit enclosed to contain noise
* Vibration resistant plastic
Figure 2.6-2b Quiet redesign highlights.
30
sound levels?
* Inner sound baffle
sound levels?
* Carburetor side enclosed
Figure 2.6-2c Quiet redesign highlights.
31
sound levels?
* The air cleaner is sound attenuated
sound levels?
* Blower tubes and nozzles were modified
Figure 2.6-2d Quiet redesign highlights.
32
Cost Comparison
PB-250LN
PB-255LN
PB-265LN
MSRP: $169.99
MSRP: $199.99
MSRP: $269.99
PB-760LNH
PB-760LNT
MSRP: $529.99 Quiet vs. $499.99 Standard (both units)
Figure 2.6-3 Prices of quieter units.
33
2.7 INFORMATION TECHNOLOGY EQUIPMENT
Marco Beltman - Intel Corporation
While the performance and capabilities of information technology (IT) products such as PCs,
notebooks, and tablets have increased dramatically over time, their noise levels have been
subsiding to often virtually imperceptible levels. Technological innovations, coupled with
information about sound levels from individual products, have contributed to the striking trend
toward quieter devices.
Marco Beltman spoke about IT equipment acoustics. First, he provided a frame of reference for
this market: Hundreds of millions of personal computers (PCs) are sold annually worldwide, and
for those selling the products, acoustical considerations are in play alongside performance, cost,
and size. In addition to desktop PCs, the IT framework is associated with a broad range of other
items including notebooks, tablets and new form factors, as well as servers and printers.
The acoustics implications and requirements for these products in actual use depend on
various factors such as:



Proximity to the user and the environment. For example, circumstances can vary greatly
between a server located in an unattended server room and a device used in a home where
people need quiet for focusing on other activities and sleep.
Customer expectations. For an original equipment manufacturer, improving product quality
and avoiding costs due to returns or service calls is critical.
Eco labels and purchase specifications. In Europe, for example, there are the Blue Angel and
Nordic Swan environmental labels and the Statskontoret technical standard. These deal with
acoustic noise, as well as other environmental factors such as power consumption and
recyclability. Though these types of standards are typically voluntary, they are associated
with an increasing emphasis on environmentally friendly, energy-efficient products and thus
help drive product development.
The EU has just put in place a regulation on environmentally friendly products that
requires manufacturers to publish noise emission levels. The rule does not require that
manufacturers meet a certain noise level, only that they publish them. By making this kind of
information available to consumers, the speaker said, a demand for quieter products is created.
Beltman next introduced the noise-related framework developed for the IT industry—
what he called “a collaboration of many, many people across many different companies.” The
speaker himself chairs the IT Industry Council (ITI) TC6, an industry trade association technical
committee relating to product acoustics. Other key groups include ECMA (originally the
European Computer Manufacturers Association) which has an acoustics group; an INCE
technical committee; and the American National Standard Institute's Standards Committee S12
Working Group 3. These groups, with examples shown in Figure 2.7-1, also work closely with
ISO and a Japanese industry association.
The goal of collaboration across companies and countries is to harmonize standards so
companies can avoid unnecessary multiple testing requirements. The harmonized global
framework informs companies of how to test and declare noise emission levels. This framework
34
includes standards such as ISO 7779 and ECMA-74 on noise level measurements and ISO 9296
and ECMA-109 on declaration of noise levels, as well as eco declarations such as ECMA-370.
Next, Beltman spoke about the technical report ECMA TR-62 and the ECMA-370 eco
declaration. ECMA TR-62 addresses product noise emissions of computer and business
equipment. One section, for example, discusses acoustic noise for tabletop personal computers,
listing the mean and standard deviation of samples from a survey. ECMA-370 speaks about
acoustic noise as well as product environmental attributes generally. Section P10 on acoustic
emissions addresses declaration of A-weighted sound power level, and refers back to ISO 9929
and ECMA-109. It also refers back to ISO 7779 and ECMA-74. This type of acoustic noise
information is publicly available on manufacturers' websites, Beltman noted.
Over the last 10 and 20 years, many technological innovations have contributed to
reduced noise, the speaker said, before touching on several examples. In efforts to address the
noise source, “huge strides” have occurred in processor and component energy efficiency. Many
systems, including notebooks, don't even have a fan in them anymore. In terms of power
management, fans and hard drive designs have improved; advances include a transition from
mechanical drives to solid state drives without moving mechanical components. And with
advanced sensing and fan control, fans can operate based on system need rather than at a
constant high level. On the transmission side, hard drive enclosure technologies—different
casing designs and new materials among them—are containing hard drive-generated noise.
The presenter next summed up desktop acoustic trend in recent decades, as shown in
Figure 2.7-2. He emphasized that large variations exist based on models, manufacturers, and
other factors, and that data points also come from divergent information sources.
Still, using orange bullets to represent average idle emission noise level, a downward
trend is evident over time. On the left side, idle noise is shown to have significantly decreased
over time, on average and under the Blue Angel eco label requirement. The right side of the
figure plots the trend for the active state—also on average and then under Blue Angel. Again a
“huge reduction” is seen, Beltman summed up, from about 5.0 bels in 1993 to about 3.5 bels
currently, which is a 15 decibel reduction. (For IT products, A-weighted sound power levels are
declared in bels instead of decibels to avoid confusion with operator sound pressure levels.)
With products quieter by more than 10 dB between 1993 and 2015, noise levels have
become comparable to the background environment, the presenter said. As long ago as 2005, a
paper co-authored by Beltman revealed that noise emission levels had already gotten so low that
devices blended into the home's background noise level. A paper1 by Robert Hellweg and
colleagues, presented at Inter-Noise 2006, likewise showed a significant downward trend in IT
noise.
As shown in Figure 2.7-3, similar trends are seen for notebook acoustic noise, again with
large variations based on different models and manufacturers. When notebooks were coming out
in the late 1990s, they were relatively noisy, Beltman pointed out, and today their idle emission
is typically around 3.0 bels or lower. In the active state, slightly greater reductions are also seen,
thanks to solid state drives. Neglecting the early noisier notebook models, in recent years there
has been approximately a 5 dB reduction in noise.
Beltman turned to the topic of perception and sound quality, discussing a study of sound
pressure levels and annoyance shown in Figure 2.7-4. The research looked at which sound
1
Hellweg, R.D., Weeren, S., and Wendschlag, H., TED - The Eco Declaration for reporting product environmental
parameters (including noise emissions) – ECMA-370.,Proc. INTER-NOISE 2006, Honolulu, HI, pp. 1590-1598.
35
quality parameters for IT products such as notebooks and desktops matter most to people. By
correlating subjective ratings with objective metrics related to characteristics such as sound level,
roughness, sharpness, and tonality, researchers found that A-weighted sound pressure level was
by far the main thing people were concerned about. People in some countries were much more
sensitive to the same sound pressure level than people in other countries. Overall, in the years
1998 to 2015, sound emitted from these IT products has gone from “slightly annoying” to
virtually “not perceptible.” These findings are in line with other data highlighting the consistent
trend in IT products: They have become much quieter while performance has continually and
dramatically improved.
Introduction
IT industry organization:

Trade association ITI TC6

ECMA TC 26 acoustics group

INCE technical committee

ANSI S12 WG3

ISO TC43/SC1/WG23

JBMIA
Harmonized standards & public information:
3

ISO 7779, ECMA-74, ISO 9296, ECMA 109

Eco declaration ECMA 370
NAE workshop “Engineering a Quieter America: Progress on Consumer and Industrial Product Noise Reduction”
Figure 2.7-1 Information sources for product noise emissions.
36
Quieter products
Example: desktop acoustic noise trend1,2:
 Large variations exist due to models, manufacturers etc
5.5
Average Idle
Average Active
Blue Angel
Sound power level LwAd (B)
5.5
5.0
Idle
4.5
4.0
3.5
3.0
2.5
1990
1995
2000
2005
2010
2015
Active
4.5
4.0
3.5
3.0
2.5
1990
2020
Blue Angel
5.0
1995
2000
Year
2005
2010
2015
2020
Year
Products quieter by more than 10 dB
Noise levels comparable to environment background
3
1
Data sheets, ECMA TR-62, internal measurements
R.D.. Hellweg, E.K. Dunens, T. Baird, “Requirements for Information Technology (IT) Equipment Noise”, InterNoise 2005
R. Doherty, E. Salskov, P. Corriveau, P. Sorenson, D. Gabel, W.M. Beltman, “Background noise levels in PC home
environments”, NoiseCon 2005, Baltimore, U.S.A.
2
3
6
Figure 2.7-2 Acoustic noise trends for desktops.
Quieter products
Example: notebook acoustic noise trend1:
 Large variations exist due to models, manufacturers etc
5.0
Average Idle
Average Active
Blue Angel
5.0
4.5
Idle
4.0
3.5
3.0
2.5
2.0
1995
2000
2005
2010
2015
2020
Blue Angel
4.5
Active
4.0
3.5
3.0
2.5
2.0
1995
Year
2000
2005
2010
2015
Year
Products quieter by ~5 dB (idle)
Noise levels comparable to environment background 2
1
Publicly available environmental data sheets, ECMA TR-62, internal measurements
2
R. Doherty, E. Salskov, P. Corriveau, P. Sorenson, D. Gabel, W.M. Beltman, Background noise levels in PC home environments,
NoiseCon 2005, Baltimore, U.S.A.
7
Figure 2.7-3 Acoustic noise trends for notebooks.
37
2020
Impact
Impact of lower levels on perception1
Germany
Extremely annoying
Sweden
US
China
Very annoying
1998
Slightly annoying
Perceptible but not annoying
2015
Not perceptible
20
30
40
50
60
Immision sound pressure level (dBA)
1
R. Doherty, E. Salskov, P. Corriveau, P. Sorenson, D. Gabel, W.M. Beltman, Human annoyance levels to PC
sounds in the home background noise environment, InterNoise 2006, Honolulu, Hawaii, U.S.A.
8
Figure 2.7-4 Study: international perceptions of noise levels.
38
70
2.8 PNR: A SIMPLIFIED PRODUCT NOISE RATING FOR THE GENERAL PUBLIC
Matthew Nobile - Hudson Valley Acoustics
PNR is a simple “product noise rating” system being developed that assigns a number to
indicate how noisy or quiet a consumer product is. A higher PNR indicates a noisier product,
while a lower PNR indicates a quieter product. This objective measure will allow consumers to
make informed purchasing decisions—like the nutrition label does for food—and promises to
motivate companies to offer quieter products.
Matt Nobile, with Hudson Valley Acoustics, spoke about PNR, a simple product noise rating
designed for the general public. As the chronology in Figure 2.8-1 shows, PNR has been in
development since 2008 by the INCE/USA Technical Committee on Product Noise Emissions
chaired by Nobile. PNR has been completed in terms of its development and design, and Nobile
focused his presentation on current status and future plans.
PNR is needed because consumers lack information about noise levels for evaluating
consumer products (though they have information on many other factors while they comparison
shop). “They essentially have no idea how loud the product will be until they get it home and
turn it on,” he said. And even then, they don't know how it compares to competitor products.
Consumers primarily want to know two things: How loud is the product (in the common,
not technical, sense of the word “loud”)? And how loud is it compared to other products?
To address these points as simply as possible with a uniform presentation, a visual PNR
icon has been developed. The PNR, shown in Figure 2.8-2, is designed with two main elements:


The PNR scale—designed on a numeric scale from 0 to 120—will tell consumers the
overall range of product noise levels (Figure 2.8-3 provides context); and
The PNR value will tell consumers where a particular product falls on the overall scale:
How loud is it?
An arrow will indicate where the PNR value for the specific product lies on the scale. The
higher the PNR, the noisier the product; the lower the PNR, the quieter the product. The label
will also include the international symbol for sound volume to drive home the fact that higher
PNRs mean higher levels of noise.
Providing noise level information to the general public will lead to lower-noise products,
Nobile said, analogizing this promise to the tremendous success of the nutrition label in leading
to more nutritious foods; the EPA mileage level in leading to better-gas-mileage cars; and energy
labels leading to more efficient appliances.
While there are some noise declarations currently, including international standards and
test codes, these types of noise appraisals are focused on industrial and professional products and
are not consumer friendly. “We need a noise declaration that consumers can easily understand,”
the presenter stated.
The presenter clarified that the PNR value describes the product's noise emission,
providing an “objective measure” of noise energy radiated from the product itself, not the noise
immission (the noise received by a person) that depends on the distance from the source, the type
of environment, and many other factors . “PNR is simply the A-weighted sound power level in
39
dB but without the dB,” he explained. The approach deliberately avoids the use of any kind of
acoustical units to help ensure the PNR's acceptability to the general public.
While a consumer will appreciate the approach's simplicity, the acoustic community
accepts the idea because it is based on over 40 years of refined sound power level standards. In
Nobile's words, “We haven't invented some newfangled metric.”
Rather than being attached to a product or its packaging, the PNR is expected to be
shown as an electronic label on a website or to appear as a physical tag on retail shelves. A
condensed PNR has been developed that shows the value without the scale, and could be used
when use of the full PNR label is impractical or unnecessary. This shortened version is shown in
Figure 2.8-4.
The INCE technical committee has also developed a preliminary website design, using
funding from INCE/USA, which will be discussed and improved before it becomes final. As an
early step, the plan is to launch an initial website to inform the public—consumers, as well as
retailers who otherwise may consider developing their own rating method—that the PNR is on
its way. This initial site will be a public comment website seeking input from stakeholders (such
as those listed in Figure 2.8-5). A PDF document is being developed for the site that visitors can
download or print out and circulate to others who may be interested.
Also, text is simultaneously being developed to incorporate PNR into standards and test
codes. Nobile suggested that PNR information could possibly be added to the American
equivalent of the ISO noise declaration standard, which is being developed by an ASA ANSI
working group chaired by Robert Hellweg.
The INCE committee working on PNR is addressing practical questions such as: “How
will we actually get PNR labels into retail businesses? Who will do this? Who will police it?
How do we update the labels?” And: Who will own this program? A separate nonprofit
organization may be needed to run it, Nobile stated.
Nobile envisions a single trade association possibly leading the way in PNR's use.
Selecting a sample product or two, such as leaf blowers, hair dryers, or refrigerators, could
elucidate the process and any obstacles. Meanwhile, one or two retailers could post some
products' PNRs on their shelves or online as a pilot.
The hope, Nobile summed up: The PNR program will grow to become widespread and
familiar to the public, and “consumers will add low noise levels to their buying decisions. People
will be asking everywhere, “What is the PNR for this product?”
Ultimately, possible benefits include:




Consumers might begin to demand, and may be willing to pay more for, quiet products.
Manufacturers may develop lower-noise products based on consumer interest.
Consumer advocate groups will have data available to earn their “certification” or “Buy
Quiet” seals of approval.
Consumer publications could include PNRs in their product ratings, making noise
measurements routine and leading to support for further standardization.
The presenter concluded: “As the general public becomes familiar with PNR ratings and
product noise in general, interest in the field of acoustics and noise control itself will increase
just as interest in the field of nutrition has increased. And because of all this, the world will
become a quieter place.”
40
PNR: Brief History -- Milestones and Public Presentations
1.
INCE BOD approval to proceed as Tech. Committee activity, 2008 Feb
2.
INCE Noise Policy Forum, Dearborn, 2008 Aug (Noise-Con 2008)
3.
CAETS Forum, Ottawa, 2009 Aug (Inter-Noise 2009)
4.
CAETS Forum, Lisbon, 2010 June (Inter-Noise 2010)
5.
EC Brussels Workshop, 2010 Oct
6.
I-INCE “Buy Quiet” Symposium, Paris, 2011 July
7.
Inter-Noise 2011 paper, Osaka
8.
NIOSH “Buy Quiet” Workshop, Cincinnati, 2011 Nov
9.
Inter-Noise 2012 “Hair Dryer” paper, New York City, 2012 Aug
10. Engaged professional design firm and developed PNR label and logo
11. INCE Board of Directors approval for $6.5K for initial website design
12. Presented to IEC Working Group that controls “Appliance Noise”
standards
13. Many INCE/TC meetings, emails, reports, BOD meetings, etc.
Engineering a Quieter America
2015 October 06-07
Slide 2
Dr. Matthew A. Nobile,
Hudson Valley
Acoustics
Figure 2.8-1 Milestones in PNR development.
Figure 2.8-2 Complete PNR label example.
41
Elements of the PNR Method: The PNR Scale
Product Noise Rating (PNR) Scale
PNR
0-20
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
Subjective Impression
at Typical Distance from
Product
Inaudible - Barely Audible
Extremely quiet
2015 October 06-07
Very Quiet
Quiet
Quiet to Moderate
Moderate
Moderate to Loud
Loud
Very Loud
Extremely Loud
Typical Products
Ticking Wristwatch
Small electric clock
Tablet Computer (with miniature fan)
Laptop Computer
Desktop Computer
Workstation Computer, Humidifier - Low Speed
Small Household Fan on Low Speed
Dishwasher, Small LCD Projector
Refrigerator, Electric Toothbrush
Small Household Fan on High Speed
Hair Dryer - Low Speed, Electric Razor
Hair Dryer - High Speed
Vacuum Cleaner
Kitchen Blender, Garbage Disposal
Orbital Sander
Belt Sander
Circular Saw
Impact Wrench
Jackhammer, Pneumatic Riveter
Painfully Loud
16
Figure 2.8-3 PNR scale in perspective (Note: the list of typical products has not been finalized
and is for illustration only).
Figure 2.8-4 Shortened PNR label example.
42
PNR Stakeholders

Nine Primary Stakeholder Groups











1. Consumers
2. Retailers
3. Manufacturers and Product Suppliers
4. Consumer Groups, NGOs
5. Trade Associations, Industry Groups
6. Purchasing Departments
7. Professional Societies
8. Testing Labs
9. Government
Each will have a role to play in PNR
Each will be invited to submit comments/feedback
2015 October 06-07
27
Figure 2.8-5 Some major PNR stakeholders.
43
2.9 AUTOMOBILE INTERIOR NOISE
Sue Sung - Independent Consultant retired from GM
Significant strides have been made with respect to noise reduction inside automobiles over the
last decade, and important technologies have contributed to this encouraging trend. Still,
challenges remain as manufacturers work to optimize noise reduction along with other
performance factors.
Sue Sung—an expert in acoustics, noise, and vibration who retired from General Motors (GM)
and consults on vehicle and powertrain noise and vibration simulation—spoke about the last
decade's progress in the area of automobile interior noise. Progress is credited to advances in
areas such as increased attention to acoustic technology applied to vehicle designs, computer
engineering applications in acoustics, increased noise and vibration testing and simulation,
advanced manufacturing technology, and the development and improved use of sound-absorptive
and barrier materials.
Figure 2.9-1 shows that the automobile interior noise results from both structure-borne
and airborne noise sources. Figure 2.9-2 then shows some of the most influential factors that
affect the structure-borne and airborne automobile interior noise performance.
Vehicle interior noise performance is considered by automobile manufacturers during the
design phase along with other performance elements such as visual appeal, fuel economy, power,
durability, safety, handling, and comfort. While fuel economy and safety are regulated by
government standards, other factors are based more on customer preferences.
To meet vehicle performance requirements, vehicle tests must be done under typical or
severe loading conditions. GM and other manufacturers take into account various driving
conditions in meeting these requirements, and with respect to interior noise performance, they
measure and benchmark road and engine noise data for their own and competitors' vehicles.
Sung summarized the methods for measuring automobile interior noise that results from
road and powertrain operating conditions. These include road tests, powertrain operating tests,
and wind tunnel tests of the vehicle.
Figure 2.9-3 shows examples of the two major vehicle noise source operations—road and
powertrain—that are used to evaluate the vehicle interior noise performance. For on-road
excitation, two measures typically used are: road noise on a coarse road at a low speed of 35 mph
to quantify structure-borne noise performance, and road noise on a smooth road at high speed of
70 mph to quantify airborne noise performance. For powertrain excitation, two measures
typically used are: powertrain noise at idle speed to quantify structure-borne noise performance,
and powertrain noise at wide open throttle (WOT) to quantify airborne noise performance. The
measures obtained are the sound pressure level (SPL) spectrum, the A-weighted sound level
(dB(A)) and the articulation index (AI). Sung's presentation results focused on the A-weighted
sound levels.
Sung explained that to quantify aerodynamic noise transmission to the vehicle interior,
wind noise is measured in a full-scale wind tunnel test facility at various airflow speeds and
angles of attack. To identify the vehicle seal performance, the interior noise is measured with and
without the seal locations being taped over.
44
To illustrate the response to road conditions, Figures 2.9-4 and 2.9-5 summarize the
measured interior A-weighted sound levels for various small and medium sedans for two road
conditions—coarse road at 35 MPH and smooth road at 70 MPH. As previously noted, coarse
road noise is due primarily to structure-borne excitation, and smooth road noise is mainly due to
aerodynamic load excitation to vehicle body panels and the door and window seals.
Figure 2.9-4 summarizes the coarse road noise over the five-year period 2000 to 2005.
For medium and large/luxury vehicles, noise shows a 5 dB(A) reduction, but for small vehicles,
the noise remains at approximately 70 dB(A), which Sung attributed to cost constraints and a
low-weight requirement for fuel economy.
Figure 2.9-5 shows smooth road noise for small, medium, and large/luxury autos over the
last decade (2004 to 2014). A consistent noise reduction trend is seen. The trend is especially
significant in small cars, thanks to stricter seal design requirements and manufacturing process
improvements to control tolerances. In medium and large/luxury vehicles, noise reduction has
resulted from the use of laminated steel and acoustically designed windshield glass. The vehicle's
architectural type also plays an important role in the acoustic flow excitation pressure on vehicle
body panels.
Engine noise is measured in an anechoic engine noise test lab under controlled speeds
and gear shift positions, with the vehicle on a chassis dynamometer. Engine performance,
including engine noise, is typically measured at idle and at WOT engine speeds. Like coarse road
noise, idle noise is primarily structure-borne.
Idle noise measurements over the last decade are plotted in Figure 2.9-6, which reveals
significant idle noise reduction over the last decade for all vehicle segments. Sung attributed this
to advanced powertrain and vehicle designs, improved powertrain mounting technologies
including actively controlled mounts, and noise cancellation in the passenger compartment.
WOT noise measurements over the last decade are plotted in Figure 2.9-7, which reveals that no
overall WOT noise reduction trend is seen. While small vehicles have generally seen noise
reduction, WOT noise for performance/luxury vehicles remains high due to demand for highpowered engines, which may be due to customers' association between this type of noise and
powerful performance.
Besides A-weighted sound levels, considerations such as Articulation Index (AI) also
reflect on performance. AI measures the acoustic environment in terms of good communication,
Sung explained—over the phone or other sound devices, for example, even in high sound level
environments.
While significant strides have been made with respect to noise reduction inside
automobiles over the last decade, the news is mixed in terms of the effect of noise technologies
during this time period. Figure 2.9-8 summarizes the vehicle interior noise measures that have
seen progress and those that have not. Various noise reduction technologies have been
incorporated into vehicles; examples are listed in Figure 2.9-9, with red dots indicating very
effective approaches and blue dots indicating somewhat effective ones.
Examples of remaining challenges are listed in Figure 2.9-10. One important outstanding
issue, according to Sung, is the problem of large noise variances from vehicle to vehicle of the
same model type, for which she also presented some published data. Updated manufacturing
processes should drastically reduce this type of variance, Sung said.
The presenter concluded by saying about luxury sport or performance vehicles that
customers driving these autos want to hear a robust powertrain sound. “It is challenging to design
45
a product with a pleasant, distinguishable, and powerful powertrain noise performance that meets
all vehicle customer expectations at an affordable price.”
Automobile Interior Noise Sources
Structure-Borne Excitation
Air-Borne Excitation
Radiated Engine
Noise
Powertrain
Dynamic
Loads
Radiated
Tire Noise
Aerodynamic
Flow (V)
Tire-Road
Loads
October 6-7, 2015
Tire-Road
Loads
Other Noise Sources
 Accessory Noise
 Squeak and Rattle
 Brake Noise
 Etc.
3
NAE Engineering a Quieter America
Figure 2.9-1 Sources of automobile interior noise.
Influences of Interior Noise Performance
Aerodynamic
Flow
Vehicle
Structure &
Architectures
Engine
RPM
Powertrain
Vehicle Speed
October 6-7, 2015
Excitations
Vehicle
Panels
Source
Inputs
Loading
Paths
Vehicle
Interior &
Trim
Powertrain
Mounts &
connections
Body
Mounts &
connections
Road Type
Receiver
Outputs
Suspension
& Tire
Other
Operating
Conditions
Figure 2.9-2 Factors that influence interior noise performance.
46
4
Figure 2.9-3 Interior noise performance: structure-borne and airborne noise.
Figure 2.9-4 Coarse road noise performance: Some small gains.
47
Figure 2.9-5 Smooth road noise performance: Noise trending downward.
Figure 2.9-6 Engine idle noise performance over the last decade.
48
Figure 2.9-7 Engine WOT noise performance over the last decade.
Summary of Automotive Interior Noise
in the Last Decade (2004-2014)
Coarse*
Road
Smooth
Road
Idle
WOT
Small Cars &
SUV
Medium Cars
& SUV
Large &
Luxury Cars
& SUV
* 2000-2005
October 6-7, 2015
Figure 2.9-8 Trends in automotive interior noise.
49
16
Noise Reduction Technology Development
Coarse
Road
Noise
Smooth
Road
Noise
Idle
Noise
WOT
Noise
Absorbers, Dampers
and Mounts
Laminated Steel
Acoustic Glass
Fitted Seal Design
Manufacturing Process
Lightweight
Absorption Materials
Body Structural
Design
Active Noise Control
Advanced Engine
Technology
Pass-by Noise
Regulation
October 6-7, 2015
Figure 2.9-9 Some effective noise reduction technologies.
Figure 2.9-10 Noise issues moving forward.
50
17
3
COMMERCIAL AND INDUSTRIAL PRODUCTS
3.1 THE NEED FOR QUIETER MACHINERY IN INDUSTRIAL FACILITIES
Robert A. Putnam - Consultant and Noise Control Engineer recently retired from Siemens
Despite a reduction over recent years in industrial facility noise, critical chasms remain in all
related areas—among them, machinery noise reduction, standards development, regulatory
compliance, and education. Noise control engineers are called upon to lead the way in filling
these gaps.
Leading off the workshop sessions focusing on commercial and industrial products, acoustical
engineering consultant Putnam spoke generally about industrial facility noise control and the
need for quieter machines in this environment. There seems to have been some reduction over
the years in industrial facility noise, according to the presenter, who left the quantification of this
progress to the following 10 presentations addressing specific components and industries. For his
part, Putnam focused his presentation on existing and foreseeable needs that noise control
engineers are positioned to help fulfill. In summing up his duties as a noise control engineer,
Putnam has said “I keep the people inside the plant from going deaf, and I keep the neighbors
from going crazy.” Thus, the principal division in his presentation separated factors inside the
plant, as shown in Figure 3.1-1, from those outside the plant, shown in Figure 3.1-2.
Putnam began the in-plant portion of the talk by focusing on in-plant regulatory
compliance. He asserted that few people, apart from acoustical and noise control engineers, are
sufficiently familiar with Occupational Safety and Health Administration (OSHA) hearing
conservation requirements and how to comply with them. In particular, Putnam highlighted two
underappreciated advantages of low-noise industrial environments habitually overlooked by
decision-making industrial facility managers and designers. First among these are the intangible
safety benefits inherent in low noise levels. Second are the benefits to increased efficiency and
productivity resulting from lowering workplace sound levels.
Those in the noise control engineering profession must continue to educate nonspecialists about the need for, and benefits from, noise improvements, Putnam stressed. These
non-specialists include everyone from equipment designers, architects and engineers (A&Es)
involved in plant and machinery design, plant managers and owners, shift supervisors, and the
employees themselves. Too often, Putnam lamented, a financial officer will say, “We're going to
postpone the installation of certain noise control measures because if it's too loud, we can always
go back and fix it.” Furthermore, A&Es with limited acoustical expertise will often include a
universal specification to the effect of “85 dB at 1 meter based on OSHA requirements.”
Misconceptions such as this regarding industrial noise control are rampant, he said. For example,
internet training module materials were shown, rife with misinformation.
Moving next to a discussion of standards, Putnam called them “vital to ensure that we are
talking to one another apples to apples across the table.” Contention often arises when noise
51
control measures are discussed, and standards allow all interested parties “to speak a common
language.” Though specifications are commonly regarded as separate from compliance testing,
the presenter said, any useful specification will incorporate compliance testing procedures, and
those who write such specifications need to understand this.
Outside the industrial plant, Putnam said, the objectives have similarities with, and
critical differences from, goals inside the plant. The principal difference is applicable local or
national community noise regulations apply outside of the plant. Considerations are summarized
in Figure 3.1-2.
“Community noise regulations,” Putnam stated, “can be clear and correct. Some are.
However, others are–we can make a list—effectively unenforceable, inappropriately imposed,
inconsistent, or just plain vague.” New and better regulations are required, along with requisite
education, Putnam said, and acoustical engineers can help with both aspects.
Next, Putnam called attention to two particular factors regarding industrial noise outside
the plant, which he believes to be habitually under-appreciated by all parties. Specifically,
community relations in general are too often overlooked in noise control decision-making.
Positive public relations are essential to the ongoing operation of new, planned, or upgraded
industrial facilities, and therefore noise control engineering plays a vital role that is too often
ignored. And the deliberately delayed installation of noise control measures can impose such an
adverse noise impact on neighbors that they become sensitized to the point that winning back
their acceptance is nearly impossible with measures installed later.
Regarding education, the presenter reiterated that all parties involved in indoor noise
decisions—from owners, operators, and A&Es, all the way down to employees—are equally in
need of education in terms of noise outside the plant. Additionally, neighbors outside the plant
must be included in educational efforts.
In addressing community regulations, Putnam touched on the importance of valid,
carefully considered community regulations, as well as clear and unequivocal equipment
specifications and compliance testing standards. He hopes for an improved catalog of standard
compliance testing procedures in the future. For instance, he noted that he is currently involved
in a revision of American Society of Mechanical Engineers (ASME) PTC 36 on measurement of
industrial sound. With this third revision, the standard will contain more detailed guidance about
such factors as close-in near-field testing and far-field multi-source testing.
Putnam concluded his presentation with a focus on “education, education, education.”
Noise control engineers are in a position to act as mentors to all players, from plant and machine
designers to the public to noise control engineers themselves. “We noise control engineers are all
mentors and we are all constantly a part of a turnover of people in standard-writing
organizations, in educational roles, and within our own industry.” As for mentoring younger
noise control professionals, he stated, “After all, noise control engineers don't come ready-made.
There is no undergraduate course out there that creates noise control engineers.” Through
educating others, Putnam concluded, experienced acoustical engineers can create an environment
that makes improved low-noise industrial environments a reality.
52
INSIDE THE PLANT
THIS SUGGESTS A “NEED”
 Machinery
Reduction
Noise
 Regulatory
Compliance &
Hearing Conservation
 Education
 Standards
Figure 3.1-1 Areas of need—inside the plant.
OUTSIDE THE PLANT
Regulatory
Compliance - AGAIN
Community Relations
– Operation/Build /Expand
Education – AGAIN
Standards - AGAIN
Figure 3.1-2 Areas of need—outside the plant.
53
3.2 AIR CONDITIONING, HEATING, AND REFRIGERATION INSTITUTE STANDARDS
AND THEIR CONTRIBUTIONS TO THE ENGINEERING OF QUIETER PRODUCTS
Steve Lind - Ingersoll Rand
AHRI standards allow users to compare equipment noise across manufacturers, which
encourages the development of quieter products. Also, with increased customer confidence
thanks to these standards, manufacturers can spend less time creating mock-ups and focus
instead on testing and improving their products.
Stephen Lind, who works for Ingersoll-Rand in the Trane Acoustics Laboratory, spoke from his
perspective as vice chair of the Air-conditioning, Heating, and Refrigeration Institute (AHRI)
technical committee on sound and based in particular on his work in the Trane acoustics
laboratory. He is also chair of the Acoustical Society of America (ASA) standards committee
S12 on noise.
AHRI and Trane primarily focus on sound power standards. Trane has been active in
acoustical standards since the mid-1960s, both at AHRI and its predecessor organization,
American Refrigeration Institute (ARI), and is also involved in ANSI and ISO standards. The
AHRI technical committee on sound is responsible for about 14 AHRI sound standards.
Lind spoke briefly about AHRI Standard 220, a reverberation room qualification and
testing procedure related to ISO 3741, but with some more stringent requirements to account for
not being able to move equipment around the reverberation room to reduce test uncertainty.
AHRI Standard 220 defines how to qualify a room and then determine the sound power, relying
on a comparison method.
Lind next explained AHRI 230, a recently adopted sound intensity standard. The Institute
has been trying to incorporate sound intensity as a viable method for determining the sound
power of equipment, he said, but found certain measurement details to be challenging.
AHRI 250 provides a calibration method for reference sound sources that uses ISO
Standard 6926; the method for determining the reference sound source sound power level is
chosen with the intent to remove some sources of variation inherent in the ISO standard. This is
very important to the industry, Lind said, because both the reverberation room standard and the
intensity standard rely on having accurate sound power for the reference sound source.
Lind next mentioned some standards for specific types of equipment, including those
listed in Figure 3.2-1. Most AHRI standards cover equipment sound power, and focus on steadystate sound. The goal is to provide information to help those responsible for acoustical analysis
install equipment in a manner that results in acceptable building sound levels.
The industry relies on various methods of sound power measurement, as summarized in
Figure 3.2-2. Reverberation room tests have been the “go-to method” for many years, he
explained, because of the number of tests required to address differences across installations.
Each installation has different heating and cooling requirements. The amount of airflow needed
and resistance caused by ductwork change with each installation, and both factors affect sound.
With the reverberation room, he stated, “we can get accurate sound measurements very quickly
for our equipment.”
Sometimes sound intensity measurements are used instead, because equipment is too
large or because a qualified room is not available. On the left side in Figure 3.2-2, a large air
handler is undergoing a ducted discharge intensity test. The bottom photo in the figure shows
54
another alternative, a test in a free-field over a reflecting plane, for instances in which the other
alternatives are not feasible. The approach requires the equipment to be set up in a large open
area or inside a hemi-anechoic space. With improvements in technology and decreasing prices
for needed equipment such as microphones and multichannel analyzers, sound power can now be
measured considerably faster than was previously possible.
The HVAC system is among the most common sources of noise in the built environment,
and is a common source of dissatisfaction. Given the difficulty of dealing with noise problems
post-construction, the goal is appropriate building design and equipment installation. Part of this
up-front process is obtaining accurate sound information from the equipment manufacturer.
For sound traveling into a certain space through various paths—including the inlet path
or the outdoor air path—sound power is typically provided to customers by octave frequency
bands. But AHRI measurement standards require that sound power be measured in one-third
octave bands so this more detailed information is available to those who are interested.
The goal is to provide information about the different ways sound will travel from the
equipment into the space, taking into consideration all equipment options and how the equipment
will operate. For this, “sound components” such as ducted discharge, ducted inlet, free inlet plus
casing, and casing radiated noise are determined. Figure 3.2-3 shows a commercial selfcontained unit in a mechanical room and the various sound paths that must be taken into account.
“The intent is that, as you're designing the building, you can calculate how all of the sound
would get into that space and what the resulting sound levels would be in that space,” Lind said.
Lind next discussed acoustics from subsystems or components versus from an assembled
unit, a topic summarized in Figure 3.2-4. It is important to note, he said, that standards take into
account the interaction of equipment components such as fans or compressors with the cabinet in
which they are placed. Because it is difficult to foresee the way sound is generated, given
unpredictable factors such as source location, directivity, and absorption, sound is much more
accurately measured with the noise sources installed in the cabinets than by separate measures of
the components with a cabinet effect added later.
Specifically, factors affecting unit sound include:



Noise sources that are aerodynamic, and the interaction of airflow with the cabinet walls
and other unit structures
o Turbulence near the fan wheel caused by the proximity of fan inlet or fan blades
to other equipment structures
o Regenerated noise—for example, when airflow is constricted or flows past an
object
Structural radiation that is difficult to predict
Attenuation due to equipment lining, coils, and some types of filters that provide
substantial absorption
Figure 3.2-5 shows an example of the substantial difference between fan-only sound
levels versus sound from the fan inside an air handler. Lind noted that fan-only standards are still
important, for designing equipment and evaluating how one fan compares to others.
Finally, Lind spoke about the benefits of AHRI standards. By allowing end users to easily
compare equipment between manufacturers or within choices from a given supplier, the
standards encourage manufacturers to provide quieter options. Standard methods can also result
in more customer confidence in the building plans and fewer mock-ups required. For example,
55
after AHRI 260 was passed in 2001, the number of mock-ups required dropped off dramatically.
Less—or no—mock-ups requested allows manufacturers such as Trane to spend more time on
equipment testing. “We are getting more data, better data on the products themselves,” Lind
concluded, “and actually spending our time on developing quieter products.”
Figure 3.2-1 Some key AHRI standards.
56
Sound Power Methods
Reverberation room when possible
Intensity because some equipment sizes
and details don’t lend themselves to
reverberation rooms
Free-field over reflecting
plane for some cases when
equipment is too large for
reverberation room and
intensity equipment is not
practical/available
Figure 3.2-2 Methods for measuring sound power.
Information provided to customers
Focus on information for good applications
– Sound power levels by octave band
• Acquired in 1/3 octaves so data is available if requested
– At conditions expected in each installation
– Sound for each of the common sound components or
paths related to the equipment
Ducted Discharge
Source: AHRI Standard 260 Sound Rating of
Ducted Air Moving and Conditioning
Equipment
Free Inlet+Casing
Figure 3.2-3 Information for customers, including comprehensive sound data.
57
Component vs Unit Acoustics
• AHRI Standards include interaction of components (e.g.
fans, compressors) with cabinet: much more accurate
– Distributed sources
– Structural radiation
– Turbulence and regenerated noise
– Aerodynamic changes
– Attenuation
• Component sound + cabinet effects can introduce
significant uncertainty/error
Fan noise generation
affected by inlet
conditions and proximity
of unit structure
Figure 3.2-4 Importance of component interaction with cabinets.
Fan only vs in unit
100
90
85
AHRI 260 ducted discharge at
2000 CFM and 4" TSP
80
75
AMCA 300/301 outlet at 2000
CFM and 4" TSP
70
65
8000
4000
2000
1000
500
250
125
60
63
Sound Power Level (dB re 1 pW)
95
Octave Band Center Frequency (Hz)
Figure 3.2-5 Fan-only, compared to in-unit, sound.
58
3.3 The Contributions of ASHRAE TC 2.6 in the Engineering of Quieter Products,
and Progress in Noise Reduction for Heating, Ventilating, Air-conditioning, and
Refrigeration Systems
Erik T. Miller-Klein - SSA Acoustics, LLP
ASHRAE Technical Committee TC 2.6 helps develop publications and standards for controlling
noise and vibration from Heating, Ventilation, Air Conditioning, and Refrigeration (HVAC&R)
systems in buildings. Among the Committee's publications is the ASHRAE HVAC Applications
Handbook (Chapter 48), and among the standards the Committee is focusing on currently is
ANSI/ASHRAE Standard 189.1 for the design of high-performance green buildings.
Erik Miller-Klein, with SSA Acoustics, spoke as vice chair of ASHRAE Technical Committee
TC 2.6 about the activities of this committee on sound and vibration. Specifically, he spoke
about noise reduction in the context of heating, ventilating, air-conditioning, and refrigeration
systems. Miller-Klein summed up the unique role of TC 2.6 within the industry, focusing on
noise and vibration, and described ASHRAE's expanded scope addressing building systems as
well as mechanical systems, as shown in Figure 3.3-1.
TC 2.6 creates and disseminates publications and standards based on information
compiled within and beyond ASHRAE. The organization's information is available for purchase
by the public. It starts with the ASHRAE Fundamentals Handbook, which includes a summary of
acoustic terminology and nomenclature used in the evaluation of sound and vibration in the built
environment.
The ASHRAE Handbook— HVAC Applications, for example, is a practical user's guide
based on over 50 years of research and information in the field of noise in buildings. It contains a
summary of research into criteria, guidelines for acceptable noise and vibration levels within
occupied spaces from building systems, and methods for calculating the sound produced by
heating, ventilation, and air-conditioning systems. It allows users to take information such as
published sound power levels for air systems and other systems and calculate how they are
expected to perform in a built environment. ASHRAE publications are summarized in Figure
3.3-2.
Miller-Klein discussed the challenge of providing enough information to engineers and
designers to help in understanding and accurately predicting how noise and vibration are
transmitted in buildings' occupied spaces. He discussed the broad areas of ASHRAE-sponsored
research, including university research that draws students to the field of acoustic research and
development.
Since 1961, ASHRAE has invested $55 million in research projects and grants on
heating and ventilation—on topics ranging from energy efficiency to acoustics. This research is
completely funded by individuals, companies, organizations, and income generated from
ASHRAE expositions. Figure 3.3-3 summarizes areas of past research successes.
Miller-Klein presented further data on ASHRAE's research: more than 700 projects since
1961, with 60 to 80 projects ongoing at any time including many multi-year projects. For each
project, a paper is published that is translated for general users. Much of the information is useful
for diverse applications—from those working on small consumer devices to full buildings.
Miller-Klein said that the ASHRAE research program is the largest program of fundamental and
applied research supported by a technical society in the world.
59
Miller-Klein summarized the process of undertaking a research project with TC 2.6, and
listed the organization's three ongoing studies: the first on annoyance thresholds of tones in
building system noise; the second on developing standard methods relating to dynamic
characteristics of vibration isolators; and the third on speech privacy and speech intelligibility in
high-performance buildings.
Looking ahead, one research topic under discussion is fluctuation criteria (how people
respond to sounds that are changing) and another is room effects (covering such factors as flow
noise and floor/ceiling constructions). Figure 3.3-4 lists other research topics under discussion.
Miller-Klein hopes that the acoustics community will come to share more information as
a way of propelling the community forward, rather than protecting information as a quality
metric or proprietary secret.
Miller-Klein next turned to the subject of standards and guidelines. People often point to
TC 2.6 information such as its HVAC Application Handbook Chapter 48 as their sound and
vibration “bible,” though the information is intended only as a guide.
Miller-Klein also spoke about ASHRAE's standards, with a focus on
ANSI/ASHRAE/IES/USGBC Standard 189.1-2014, Standard for the Design of HighPerformance Green Buildings. Standard 189.1 covers all building systems and defines acceptable
average and maximum sound levels, with consideration to interior noise sources, elevators, and
air systems and also exterior noise impacting the spaces. Though its standards are currently not
enforceable, TC 2.6 aims to convey to the building community that acoustics as addressed in
Standard 189.1 deserves a place next to light and energy efficiency in designing a truly “highperformance” building (as described in Figure 3.3-5).
Miller-Klein concluded that ASHRAE TC 2.6 “is concerned with the fundamental
scientific and engineering principles of sound and vibration, particularly as applied to the design
and performance of the built environment.” TC 2.6 will “provide effective tools and research to
assist all industries with their noise control efforts,” he said. “If we want to really move the
acoustics community forward, we [acoustics professionals and noise control engineers] have to
be able to share information … better so that we all improve”.
Responding to a question, Miller-Klein said ASHRAE's resources have achieved
advances toward better-designed, quieter buildings, but that “teeth” are needed for more
consistent acoustic performance. Energy efficiency has been the only requirement to define a
building as high-performance (or green), but Miller-Klein said it is quite possible that Standard
189.1 for high-performance buildings will become part of building codes in the next decade for
many U.S. cities, counties, and states. Very few acoustical building code criteria currently exist,
and converting Standard 189.1 from a best practice to an enforceable section in Green Building
codes (IgCC*) would be the “meat on the bones for acoustics.”
*IcGG – 2012 International Green Construction Code
60
Scope
• TC 2.6 is concerned with the fundamental scientific and engineering
principles of acoustics and vibration, particularly as they are applied
to problems of sound and vibration associated with the built
environment.
• Expanded scope includes architectural design and all building systems started
in 2013
• Origins in heating, ventilating, air-conditioning and refrigeration systems.
• Committee is made up of acoustic consultants, manufacturers, and academics
Figure 3.3-1 ASHRAE TC 2.6 expanded scope.
Standards & Publications
• Fundamentals Handbook, Chapter 8
• Summary of acoustic terminology and nomenclature used in the evaluation of
sound and vibration in the built environment
• HVAC Application Handbook, Chapter 48
• Summary of decades of research into criteria, guidelines for acceptable noise
and vibration levels within occupied spaces from building systems, and
methods for calculating sound from heating, ventilation, and air-conditioning
systems.
• Application of Manufacturers’ Sound Data (Blazier and Ebbing)
• A Practical Guide to Noise and Vibration Control for HVAC Systems
(Schaffer)
Figure 3.3-2 ASHRAE acoustics publications.
61
Areas of ASHRAE Research
Areas of Past Research Successes:
• Thermal Comfort & Indoor Air Quality (IAQ)
• Sound Criteria & Attenuation Methods
•
•
•
•
•
•
Property Data for Refrigerants, Other Materials & Food
Heating and Cooling Load Calculation Procedures
Weather Data
Simplified Energy Analysis Procedures
Cooling & Heating Applications Using Alternate Energy Sources.
Fire & Smoke Control Tests & Algorithms
Figure 3.3-3 ASHRAE research successes.
Acoustics Sponsored Research
• TC 2.6 champions ideas and areas of research within the
society to improve acoustical knowledge and algorithms.
•
•
•
•
•
Indoor Sound Criteria
Sound attenuation in ductwork
Determining Attenuation of Sound in Lined and Unlined Ductwork
Aero-Acoustic effects of inlets, plenum, and fans
Relationship Between Low-frequency HVAC Noise and Comfort in
Occupied Spaces
• Reflection of Airborne Noise at Duct Terminations (end reflection)
• These research projects are the foundation of the ASHRAE
Handbook Chapter 48 Sound and Vibration.
• Commonly cited section for vibration isolation and sound
attenuation for building systems.
Years
Number of
Projects
1965 – 1969
2
1970 – 1974
2
1975 – 1979
2
1980 – 1984
5
1985 – 1989
5
1990 – 1994
1
1995 – 1999
3
2000 – 2004
3
2005 – 2009
5
2010 – Present
6
Total
Figure 3.3-4 ASHRAE-sponsored acoustics research.
62
32
Benchmark Acoustic Research
• Noise Generation in Ducts (1965) – Uno Ingard, Industrial Acoustics
• A Study to Update Indoor Sound Criteria for Air Conditioning Systems (1975) – Louis
Goodfriend, Louis Goodfriend & Associates
• A Study to Determine Attenuation of Sound in Lined and Unlined Ductwork (1977) –
I. Ver, Bolt Beranek and Newman
• Improved Reliability of the Relation Between Sound Power Level and Sound Pressure
Level (Room Effect) (1983) – T. Schultz, Bolt Beranek and Newman
• Determination of Effect of Ceiling Systems and
Plenum Sound Power Radiated Through Ceilings
by Terminal Units (1997) – A.C.C. Warnock,
National Research Council of Canada
• Numerical Methods for Low-Frequency HVAC
Noise Applications (2006) – David Herrin,
University of Kentucky
Figure 3.3-5 ASHRAE benchmark acoustic research.
Future Research
• Funding acoustic research that covers the expanded scope of building
systems and the built environment.
• Currently in discussion, though outside ideas are welcome:
•
•
•
•
•
•
•
•
Fluctuation criteria
Room effects
Flow noise and insertion loss within ducts, louvers and dampers
Noise intrusion from exterior or adjacent spaces
Dynamic properties of building floor/ceiling constructions
Evidence based criteria
Non-fibrous duct liners
Plumbing noise
Figure 3.3-6 ASHRAE future acoustic research under discussion.
63
New Standards & Initiatives
• ANSI/ASHRAE Standard 189.1 Standard for the design of highperformance green buildings except low-rise residential buildings
• Working to integrate comprehensive acoustic criteria for high performance
buildings, including interior noise, sound transmission/footfall, and
reverberation time
• This standard is being adopted as code within certain building sectors and
regions
• Support the development of standards with ANSI with respect to
mechanical systems and buildings.
Figure 3.3-7 ASHRAE and high-performance green buildings.
64
3.4 Large Industrial Air Movement Devices
Dr. Geoff Sheard - AGS Consulting, LLC
As new regulations take effect and consumers push for more efficient, less noisy fans, the air
movement fan community is relying on continually improving computational capability—and
taking a page from the aerospace fan community's handbook.
Geoff Sheard, president of AGS Consulting, LLC, spoke on behalf of the Air Movement and
Control Association (AMCA), in his capacity as chairman of its board of directors. AMCA
represents air movement fan manufacturers worldwide.
Sheard kicked off his presentation by explaining that the air movement and control
community has a single major international conference every three years, which reflects the
community's interests and progress during the intervening time period. The conferences used to
focus on empirical research and experimental methodology, but the last two—“Fan 2012” and
“Fan 2015” in April of each year—saw the first papers that systematically applied computational
methods to predict flow-field features and correlate them with fan acoustic emissions. By 2015
the majority of research focused on application of computational methods to the prediction of fan
broadband noise and spectrum. Enhanced computational capability has been credited at least in
part for this trend, as it allows academics using large eddy simulations to conduct flow-field
simulations accurate enough to predict the features that constitute the near-field aerodynamic
origin of fan far-field noise.
The practical challenge: large eddy simulations require 100 to 1,000 times the
computational capacity available to even the largest air movement fan manufacturer. While this
problem may be overcome in the next few years, according to Sheard, academic researchers have
access to computer clusters today that make the computational effort associated with large eddy
simulations less of an issue. However, because of computational demands, interest remains in
semi-empirical and hybrid methodologies for predicted fan noise that require a small fraction of
the computational effort associated with large eddy simulations.
In its review of the Fan 2015 conference, AMCA concluded that, to meet forthcoming
regulatory requirements, the rate of new product development would have to increase by
approximately an order of magnitude by the end of the decade. Computers will be used to predict
fan noise, as well as performance, because time-consuming traditional approaches to
experimentally characterizing fan performance and fan noise will impede the industry's ability to
develop new products that comply with forthcoming regulatory requirements.
Forthcoming regulations include increased minimum allowable fan efficiency levels in
Europe and new minimum allowable fan efficiency levels in the U.S. The changes are expected
to take effect around the end of this decade, and according to Sheard, both are driven by an
underlying assumption that fan efficiency can be increased while maintaining acoustic
performance. Regulators in both Europe and the U.S. carefully considered the consequences of
minimum allowable efficiency levels for fan manufactures. However, this consideration was
within the context of energy saved and the percentage of fans currently sold that would not reach
minimum efficiency levels. There was little consideration of the acoustic consequences of
imposing minimum efficiency levels.
Sheard's example: a forward-curved centrifugal fan is compact and quiet but inefficient.
Forward-curved centrifugal fans may be regulated out of existence because it is not feasible to
65
increase their efficiency even when optimized using simulations requiring a very large computer.
In contrast, a backward-curved centrifugal fan, built to be efficient at a similar size to a forwardcurved centrifugal fan operating at the same duty point would be relatively noisy. Further, using
an axial fan for efficiency and acoustic performance would call for a significantly larger device.
Next, Sheard described two fans—one with market demands pushing pressuredeveloping capability, assuming that fan noise can be held constant; and the other with the
market requiring performance to stay constant, but driving acoustic emissions down. The first is
a tunnel ventilation fan, and the pressure developing requirements have been roughly tripled by
new tunnel designs.
A primary contributor to the pressure loss through a tunnel system is the loss through
ventilation shafts. In longer tunnels there is a need for ventilation shafts along the tunnel to
maintain pressure loss below pressure developing capability of the selected tunnel ventilation
fans. If the number of ventilation shafts is reduced, tunnel pressure loss between ventilation
shafts increases. If the diameter of ventilation shafts is reduced, velocity increases within the
shaft and consequently so does pressure loss.
A two-pronged approach to minimize tunnel construction costs is to reduce both the
number of ventilation shafts and the diameter of those that remain. It is therefore a desire to
minimize tunnel construction costs that has resulted in the need for increased tunnel ventilation
fan pressure developing capability. However, the required increase in tunnel ventilation fan
pressure developing capability overpasses the pressure developing capability of a single fan
stage. So alternatives must be examined.
Sheard discussed the three alternatives shown in Figure 3.4-1. One involves two counterrotating stages. Another is to switch from aluminum to titanium and simply run the fan faster.
The third is a two-stage co-rotating fan. In his example, the three alternatives each have the same
inlet and exhaust noise level, so the size of the silencers is a proxy for the fan's acoustic
efficiency. The two-stage co-rotating fan shown in Figure 3.4-1 is significantly more acoustically
efficient and, therefore, more desirable.
The speaker presented a CAD view of the co-rotating fan, whose motor has a doubleended shaft and an impeller stage on each end as shown in Figure 3.4-2. This option requires
design expertise more characteristic of industrial turbomachinery than fan technology. If
designed without due care to the aerodynamic performance of inter-stage vanes, the flow
separates and broadband noise increases. These two stages rotate together on different ends of
the same motor shaft, and can be “clocked” relative to one another. In this context, the term
clocked refers to the practice of building the fan with the blades of the first impeller at a different
angular position to the second. If they are inappropriately clocked, you get an undesirable tonal
peak—by Sheard's description, “It howls like a banshee.” In this case, traditional fan technology
falls short; the design requires adoption of methods originally developed by the aerospace fan
community.
The second example—a fan over a tube bank shown in Figure 3.4-3—involves a fan that
is not as large, but is in some ways more demanding. This intensely competitive market segment
is driven by a desire for the lowest possible noise. Around the year 2000, the air movement fan
community effectively reached the limits of traditional fan technology. As the market continued
to push for lower noise, the air movement fan community was driven to adopt experimental and
computational methods originally developed within the aerospace fan community.
Sheard next presented an example of the experimental data shown in Figure 3.4-4, taken
using an aerospace-developed measurement technique applied to measure the acoustic emissions
66
of an air movement fan. The figure shows:


A radial distribution of noise from blade hub to tip
Normalized frequency where 1 is blade-passing frequency, and 2 is the first harmonic,
with the data being the coherence between near- and far-field noise.
This has allowed engineers to elucidate the different fan noise sources. Computational methods
may then be used to predict the existence, intensity, and trajectory of flow-field features
experimentally identified as acoustically productive. See Figure 3.4-5.
In combination, the experimental and computational methods may be used to both
identify noise sources and predict the location and intensity of the flow-field features that
constitute the origin of these noise sources. The experimental and computational methods form
the basis of a methodology that facilitates optimization of blade-tip end-plate design. This
optimization eliminates or minimizes the near-field flow features that are acoustically coherent in
the far-field.
The result of the first application of the methodology is a series of the prototypes shown
in Figure 3.4-6. The final design, more three-dimensional than its predecessors, achieved a
significantly lower-noise fan than any other marketed fan in its application. This design—which
was successfully patented—was only possible using the combination of experimental and
computational methods developed for the aerospace industry. It is labeled MVB in Figure 3.4-6.
Sheard reiterated that, given regulatory pressures on fan efficiency, some non-compliant
products are rendered nonviable. Meanwhile, consumer demands are causing the air movement
fan community to develop products in ways more typical of the aerospace fan community. The
choice is straightforward, he stated: “Pack up and go home or develop new products. I think
some will choose to pack up and go home. However, most will choose to develop new products.”
67
Figure 3.4-1
Example of three fan concepts, each designed for the same aerodynamic
operating point with silencers sized to give the same overall inlet and exhaust
noise. The silencers associated with Concept 3 incorporating a double ended
motor are significantly smaller than the alternatives.
68
Figure 3.4-2
Example of a reversible tunnel ventilation fan incorporating a double-ended
motor. The design of inter-stage vanes has an impact on the magnitude of fan
broadband noise. The relative angular position of one impeller relative to the
other has an impact on the magnitude of fan tonal peaks.
69
Figure 3.4-3
Example of a compact cooling unit fan fitted over a tube bank. The fan is an
induced draft fan, drawing air over the tubes of the tube bank. The fan inlet flow
is consequently both distorted and turbulent, increasing fan noise in an
application demanding low noise.
70
Figure 3.4-4
Example of laboratory data from a compact cooling unit fan measured using a
measurement technique originally developed by the aerospace fan community.
Noise control engineers working in the air movement fan community further
developed the technique. When developed, the technique facilitated
identification of fan rotor noise (RN), induced noise (IN), motor noise (MN),
turbulence induced noise (TIN), and secondary flow noise (SFN). In so doing
noise control engineers were able to gain an insight into the near-field
aerodynamic origin of fan far-field noise. This insight enabled them to develop
fan geometry, minimizing or eliminating those flow-field features responsible for
far-field noise. When built and tested, the developed compact cooling unit fan
had the lowest noise in its class.
71
Figure 3.4-5
Example of the results of a computational simulation of the flow-field though a
fan intended for application in compact cooling units. The method used facilities
identification of the intensity and trajectory of near-field flow-field features that
constitute the origin of fan far-field noise.
72
Figure 3.4-6
Example of prototype compact cooling unit blade tip end-plate designs. The final
design (MVB) reduced fan far-field noise to the lowest in its compact cooling
unit application.
73
3.5 INDUSTRIAL POWER GENERATION EQUIPMENT
James Barnes - Acentech Incorporated
Progress in noise reduction in the power generation context—including improved designs for
fans and transformers—has been coming to wide-ranging kinds of plants. Local residents and
workers alike are benefiting from steps being taken for sound attenuation.
James Barnes, with Acentech, spoke about noise themes within the power industry. He opened
by speaking about trends in this arena. Regulatory requirements put in place by OSHA and state
and local authorities are driving forces in noise control in new plants, he said, along with
changing community and worker expectations.
With deregulation a couple of decades ago, new power industry players including lowcost companies stiffened competition in the industry, increasing pressure to manage costs such as
capital and operating costs and in turn protect profits. Significant advances have occurred to
benefit the noise environment and preserve acoustic integrity which, Barnes said, “tends to be
value-engineered out of projects.” Plant control and monitoring systems, though not direct noise
technologies themselves, have achieved noise reduction by avoiding issues associated with
unnecessary steam releases and inefficient operation of equipment within the plants.
Barnes next summed up some industry trends—for example, a changing fuel mix from
coal to oil, and then back to cleaner coal designs; and significant electrical capacity still provided
by the nuclear industry although new plants have not been built. And he talked about plant types,
generally, as shown in Figure 3.5-1. These include the classic coal-fired power plant that is
located by a river or lake for fuel delivery and heat exchange, and relies on stacks for air and gas
movement. To achieve this movement, very large fans are required, including forced-draft fans,
induced-draft fans, and sometimes combustion air fans. About 20 years ago, the gas-fired
combined-cycle plant became a standard type. This plant uses what has been referred to as an
industrial turbine, which resembles a jet engine and which, combined with a heat recovery steam
generator, is highly efficient at generating electricity. A power generator supported by many
communities today is a combined heat and power plant, and in some cases, also a cooling plant
with steam absorbers. The plant is located within the community, near the actual demand,
eliminating the need for major transmission lines. Finally, wind turbines represent another power
generation alternative that can have associated noise.
Barnes next introduced some primary noise sources in various types of plants, which are
shown in Figure 3.5-2 with overall sound power level estimates normalized to a plant rating of
100 MWe. Coal-fired plants are near the top in terms of noise, at up to about 123 dB(A). The
simple-cycle turbine plant is at 100 dB(A), and the combined-cycle plant at 94 dB(A)—that with
noise control measures in place. With additional noise reduction steps, the gas turbine combinedcycle plant emits noise at only about 89 dB(A). “That's a pretty modest amount for putting out
that much electricity,” Barnes noted. As for wind turbines, at a 109 dB(A) level, this very
distributed energy source produces a great deal of sound on a per-megawatt basis.
Next, the speaker focused briefly on noise factors for combined-cycle turbine power
plants. Sources of noise can include fuel gas flow as it enters the site; an on-site fuel gas
compressor; a combustion turbine generator that is enclosed and typically indoors; a heat
recovery steam generator that may be indoors or outdoors; an air-cooled condenser or wet
74
mechanical draft cooling tower with very large fans; and electricity that exits and travels to stepup transformers.
Neighbors living relatively nearby benefit from any noise reduction steps put in place,
Barnes pointed out, and workers have benefited from some protections such as locating highlevel noise sources in their own isolated rooms and designing effective enclosures for
combustion turbines.
Owners interested in improving plant interior sound have options for attenuation. For
example, acoustic blocks can be used in place of concrete masonry units (CMUs). In smaller
plants such as those used for hospitals, universities, and research facilities, treated ceilings are
becoming more common. And sound absorption can also be considered when a steel roof deck is
selected.
Variable frequency drives (VFDs) designed for maximum loads can effectively reduce
noise. “Rather than choking everything down with flow control devices, one can slow the
machine down and get dramatic reduction with both lower-noise operation and lower energy
use,” the speaker said. Pumps and fans, in particular, can benefit from this approach.
Showing an aerial photo of various types of packaged cooling towers, Barnes stated that
towers with wider-chord fans are typically quieter, benefiting from fans running at slower tip
speed while still delivering the necessary amount of air. The potential downside: these towers
shift the sound spectrum so that more distant neighbors may be exposed to additional lowerfrequency sound.
Barnes next spoke about sound from reduced-speed fans and low-noise fans, as shown in
Figures 3.5-3a and 3.5-3b. Reducing from full speed to half speed—following fan laws, at about
55 times the log speed ratio for a packaged tower—the blade passing frequency and its second
harmonic drop significantly, and as expected, the overall level reduces from 94 to 76 dB(A). By
switching to low-noise fans (for example, by moving from 12 blades to 6 more aerodynamic
ones), real reduction can be achieved even while maintaining the same required fan capacity.
“You can see we are getting some nice broadband reduction,” Barnes said.
Barnes next addressed reduced-noise transformers with their more aerodynamic fan
designs and improved internal core and external casing constructions contributing to the sound
reductions as reflected in Figure 3.5-4. Measuring close in, the average overall sound level was
on the order of 63 dB(A) with all fans operating, compared to the standard NEMA “benchmark”
level of 77 dB(A). Efficient transformers are achieving much lower sound levels than standard
NEMA levels, Barnes explained, as people have become willing to pay an up-front premium to
achieve the energy saving payback over time, and as improved transformers that are designed
and built for low noise—perhaps 5 to 10 dB(A) or more quieter—become available.
As for wind turbines, the design has been improved by placing blades upwind of the
tower to avoid the “siren” effect inherent with the obsolete downwind turbine; using quieter
gearboxes; improving the design of the nacelles containing the gearboxes; improving the blades
(using a serrated blade on the trailing edge, for example); and improving monitoring so that pitch
and yaw can be better controlled.
To conclude his talk, Barnes talked about his predictions for the future of industrial
power generation. Smaller plants will become more common; regulatory pressures will be
ongoing; and people will be willing to pay more for noise control. Barnes said, too, that a softer
acoustic environment could potentially raise productivity, communication, and the ability of
workers to identify steam leaks and other equipment failures.
75
Trends – Plant Types
Coal, Nuclear, Gas Turbine Combined-Cycle, Combined Heat & Power, and Alternative Plants
TQA Follow-up 2015
Figure 3.5-1 Common power generation plant types.
Estimated Overall LwA for Various Types of
Power Plants (Normalized to 100 MWe Plant)
TQA Follow-up 2015
Figure 3.5-2 Sound levels for power plant types.
76
Reduced-Speed Fans
Reduce to
50% full speed
(12-bladed fan with narrow chord)
TQA Follow-up 2015
Figure 3.5-3a Sound measurements: reduced-speed fans.
Low-Noise Fans
12 Blades
6 Blades
TQA Follow-up 2015
Figure 3.5-3b Sound measurements: low-noise fans.
77
37/50/65 MVA Transformer
Measured:
58/62/63 dBA
vs.
Std. NEMA Levels:
74/76/77 dBA
TQA Follow-up 2015
Figure 3.5-4 Efficient transformers emitting less noise.
78
3.6 ADVANCED NOISE CONTROL TECHNOLOGY FOR
ELECTRICAL POWER GENERATOR SETS
Shashikant More - Cummins Power Generation
Cummins, Inc., has built a state-of-the-art “Acoustical Technology Center” for the design and
development of quiet products. The sophisticated, largest-of-its-kind facility was designed and
constructed to develop quiet electrical power generator sets to meet the noise goals of customers
and requirements of countries around the world.
Shashikant More is the Acoustics and Vibrations leader for global power generation for
Cummins Power Generation, but presented his own perspective on the development of quieter
electrical power generator sets (“gensets”). In addition to discussing progress, he spoke about the
standards used to govern the noise measurement process and how regulations are shaping noise
control goals.
Cummins Power Generation built a state-of-the-art “Acoustical Technology Center”
(ATC) that is the largest facility in the world in the diesel and power generation industries. As
listed in Figure 3.6-1, among other relevant standards and regulations that shape product design,
ISO 8528-10 and ISO 6798 are two standards that speak specifically to power genset noise
measurement, diesel engine noise measurement, and exhaust system noise measurement. ISO
6798 is used to characterize exhaust noise from a diesel engine. The European Union (EU)
Directive 2000/14/EC on noise from equipment for use outdoors, known as a CE (Conformité
Européenne) regulation, is another primary regulation applicable to the company's products,
applicable to outdoor products specifically. And India’s CPCB-II regulates noise as an emission
pollutant.
Cummins invested heavily in developing a noise measurement system to support the
design of quiet products. For decades, the company had used its open-air atmosphere “sound
pad” located in Minneapolis. But it built its multimillion dollar Acoustical Technology Center,
shown in Figure 3.6-2, in part to address the limitations of this sound pad for running big
gensets, such as very cold temperatures, several months of snow each year, and property line
noise restrictions. The center is the world's largest chamber in the power generation business—
105 feet long, 80 feet wide, and 36.5 feet tall (about 32 meters long, 24 meters wide, and 11
meters tall). The entire semi-truck with the trailer genset can enter through the main 16-by-16foot door (about 4.9-by-4.9 meters). The facility has two “massive” air mixing chambers that can
satisfy the air requirements for maintaining environmental conditions recommended per ISO
3744 and ISO 3745 standards. Two silencers reflect the company's commitment to quietness for
the community when exhaust is emitted in the open-air atmosphere. The chillers are required
because the facility supports all Cummins products, including diesel engines without cooling
systems.
More described the building, which has already been cleared for the next 30 years, as a
“futuristic vision.” The chamber can accommodate at least a 120-liter diesel engine genset,
which means a 4.4 megawatt capacity engine genset. In 2011 the company performed the
qualification under ISO 3745 and ISO 3744. Although the hemi-anechoic chamber was specified
for a 50 hertz cutoff frequency, the building is actually a precision-grade facility, with the
controlled area allowing for a 25 hertz cutoff frequency for most Cummins products.
79
A background noise measurement was also performed in the building, which has various
ventilation modes. For breathing air—general ventilation mode—the noise level was almost 15
dB(A). This, More explained, is an NC-20 criterion-based background noise level chamber.
Different modes apply to different genset sizes, with mode 4 being the highest mode, meaning
massive amounts of air. Even with some 222,500 cubic feet per minute of air in the chamber
(about 105 cubic meters per second), the state-of-the-art air handling system gave an NC 35
background noise criterion. This makes the largest facility in the world of its kind one of the
quietest, as well.
More explained the massive amounts of air are needed because the building is an
environmental parameter controlled facility. The chamber maintains a constant temperature of 23
degrees Celsius and a humidity of 50 percent. The barometric pressure is relatively constant due
to the height from sea level, but the small perturbation in barometric pressure is measured. With
this environmental parameter control, the noise data is associated with a zero correction factor.
At the facility, noise is measured for the 3 kilowatt to 3,500 kilowatt gensets (based on
the largest current product, though this can increase). The facility, which uses all Class 1
instrumentation, can accommodate 136 channels at a time. Its acoustic measurement capability is
summarized in Figure 3.6-3.
The sophisticated facility, and Cummins' huge range of products, is the “tremendous
advantage” that helps the company to develop the quietest possible products, More said. The
facility is so busy that projects are typically booked six to seven months in advance.
Figure 3.6-4 shows the use of microphones for conducting noise measurements at 1 and 7
meters to meet worldwide requirements such as those listed, which include requirements in the
U.S. and also in Europe and Asia. “We are able to produce a spec sheet for different
modifications by just taking the data once,” More explained.
Figure 3.6-5 lists the various product noise goals—many set by customer demands and
others arising from regulations. More stated that customers—even in Australia, the Middle East,
or South America—often consider CE as the quality benchmark.
The CE regulation has A-weighted sound power level as its primary metric, and limits are
applicable to gensets up to 400 kilowatts (15-liter diesel engine genset). Above 400 kilowatts,
noise levels must still be measured and displayed. Figure 3.6-6 summarizes the CE and the
CPCB-II noise limits. It is “compulsory for us to meet those if we want to sell that product in the
market,” More emphasized. “This is the governing equation for meeting the noise goals and
coming up with the quietest product.”
More also said that a few years ago, Cummins adopted a “Buy Quiet” principle as
described in Figure 3.6-7 in place of “Quiet by Design.”
More next presented a case study in which two air filter options were considered, leading
to the selection of the heavy-duty one. The heavy-duty filter might have been rejected on the
component level in favor of the normal-duty one, based on such factors as cost. But at the system
level, it was determined that the noise levels would have required a very costly enclosure design
to compensate for the unacceptable levels of middle-frequency and low-frequency noise. By
looking at the system level, More summed up, “ultimately we save a lot and then we also are
able to meet the noise goals and produce the quietest possible product.” The Acoustic
Technology Center has “perfected” the noise modeling technique for designing an enclosure,
said More. He next described the analysis-led design approach that Cummins uses to influence
the virtual build and, in turn, to devise optimal noise control strategies.
80
Cummins has developed a very quiet “T-series” product line with “Silent,” “SuperSilent,” and “Ultraquiet” gensets. More concluded his presentation by playing sounds measured
at 1 meter and 7 meters (about 3.3 ft and 23 feet) from an operating genset, along with music and
then human conversations. First he played the sound from the Ultraquiet genset at 1 meter and at
7 meters. At the 7-meter distance, “you're not really going to hear the genset, just the music
signal,” he pointed out. Next, he played human conversations at distances of 1 and 7 meters. The
Ultraquiet gensets were so quiet that speech intelligibility was high. “So this is how we work on
the sound quality,” More concluded. “And so noise levels are not a big deal for us anymore.”
Figure 3.6-1 Primary applicable standards and regulations.
81
Figure 3.6-2 Cummins' sophisticated Acoustical Technology Center.
Figure 3.6-3 ATC's measurement capability.
82
Figure 3.6-4 ATC's set-up for noise level measurement.
Figure 3.6-5 Noise limits for power gensets.
83
Figure 3.6-6 Noise limits: CE and CPCB-II.
Figure 3.6-7 Approaches to noise control.
84
3.7 INDUSTRIAL MOTOR NOISE CONTROL: HISTORY, COSTS, AND BENEFITS
Arno Bommer - CSTI Acoustics
The extent of noise from motors varies greatly depending on factors such as enclosure type,
speed, horsepower, and cooling method. Noise control treatments vary, too, depending in
particular on the source. While noise management standards and regulations can apply,
industry's lower noise goals—coupled with its firm demands for less noisy products—can be at
least as important in making quieter motors a reality.
Arno Bommer, with Collaboration in Science and Technology, Inc., (CSTI) presented a paper on
motor noise control on behalf of primary author Robert Bruce. Motors are ubiquitous, Bommer
said, representing nearly half of the estimated share of global electricity demand by end use, and
are used primarily in industry but increasingly in other areas as well (in cars, homes, etc.).
Induction motors, which are relatively inexpensive, are commonly used but have the
downside of slowing under load. Synchronous motors cost more, but offer the sometimesessential ability to run at a fixed speed.
A major difference among motors is the type of enclosure used, which affects noise
containment. Three enclosure types are shown in Figure 3.7-1—the open drip-proof (ODP) type
for indoor use; the Weather Protected II (WPII) kind, a larger motor that is fairly weatherproof
and commonly used outside; and the mainstay of motors, the totally enclosed fan-cooled (TEFC)
motor, which is completely enclosed and cools by airflow over the ribs on its side. The TEFC is
basically a heat exchanger, Bommer explained, which can be used in any environment, including
outdoors, and may be the most common general type.
Different noise regulations relating to such factors as sound pressure level and sound
power level can apply depending on the location of the motor's operation. Industry standards
exist, as well, such as IEC 60034-9, summarized in Figure 3.7-2, that provides certain levels that
must be met based on horsepower, RPM, enclosure type, and cooling type. The National
Electrical Manufacturers Association (NEMA) has standards for enclosure types. In terms of
government regulations, OSHA and EU spell out limits aimed at preserving hearing, and local
authorities sometimes regulate motors to diminish annoyance from noise.
Next, Bommer addressed the history of noise control. Once, industrial hygienists had a
primary role in the field. By the 1960s and 1970s, acoustical consultants were often relied on to
help meet OSHA regulations. And noise-control companies began to manufacture treatments
such as mufflers and to perform retrofits.
The speaker next summarized major noise sources from motors: aerodynamic sources
(primarily from cooling); magnetic sources; and general mechanical sources. Sound level
depends mostly on speed, horsepower, enclosure type, cooling method, and noise control efforts.
After showing the expected trend of increased noise with increased horsepower, Bommer
mentioned the progressively—and expectedly—higher noise levels with TEFC, ODP, and WPII
enclosures, as shown in Figure 3.7-3. Figure 3.7-4 depicts a similar analysis based on frame
design or frame size (basically, equivalent to horsepower): Generally, larger frame design means
more horsepower means more noise.
Aerodynamic noise can be the dominant noise source, especially with a high-speed fan
mounted directly on the motor shaft. Magnetic noise can dominate once fan noise is addressed.
Third, mechanical noise from general operational vibration can be another major source. And,
85
with variable frequency drives (VFDs), using varied electrical current to run at lower speeds can
result in a loud, high-frequency hum at a certain carrier frequency.
Bommer next addressed noise treatments. Historically, a noisy paddle-type fan was used,
but updated designs emit less noise. Varying the spacing of blades helps attenuate the tone at the
blade pass frequency, for example. Reducing the fan diameter is an option, though this approach
affects airflow. Porous materials may help. Bommer pointed to the data (albeit older
information) from Figure 3.7-5 showing the 10 dB or so noise reduction achievable by switching
from a nondirectional to unidirectional fan.
Various approaches can reduce aerodynamic noise, including using a quieter fan;
ensuring a minimum distance between operating fan blades and stationary parts; reducing rotor
vents; lining air chambers with sound absorptive materials when possible; or adding a motor
mute on the end of a TEFC motor for sound reduction.
As for magnetic noise from strong magnetic fields inside the motor, Bommer explained
the amount of sound varies depending on flux densities. Sound reduction options are summarized
in Figure 3.7-6. The goal is to get tangential forces on the rotors, which can be done using
today's improved computational methods to avoid resonances in the design and reduce
generation of sound and vibration.
Addressing mechanical noise involves using the best bearings possible, achieving optimal
balance, and designing a system to avoid any resonances so the driving frequency does not match
up with the system's structural resonances.
Bommer focused next on cooling method, which is often the noisiest, especially when
cooling air is taken from and discharged to the atmosphere. One relatively quiet approach is the
use of water-cooled motors, which have no vents and rely on heat exchangers so air blows
around inside the motor. Figure 3.7-7 presents data comparing air-cooled versus water-cooled
motors for driving large pumps.
Active noise cancellation has been tried without great success. Pulse width modulation, in
which the incoming electrical signal is varied, can be helpful for electromagnetic noise if load
varies. An energy-efficient motor can of course reduce noise by reducing reliance on cooling,
Bommer added.
On the subject of motor noise itself, the speaker emphasized that this noise must be
considered in the context of noise from the equipment (such as a compressor) that the motor is
driving. Motors are often tested at no load, reducing the practical usefulness of measurements,
but standards can provide corrections to predict noise under load.
On the advantages of being quieter, Bommer spoke first about cost. While exact figures
are hard to come by, achieving a 5 to 10 dB noise reduction typically results in an extra 5 to 10
percent in motor cost. An additional 10 dB reduction would naturally be expected to cost more.
Where industry in the past typically expected a noise level of about 90 dB(A) at 1 meter,
over time these expected levels have been reduced to 85 dB(A) and lower. Goals are one thing,
Bommer said, but often people accept noisier products. Real improvements will occur, he said,
when people “really stick to their guns and require these levels.” He concluded, “Trying to get
total packages down to 78 dB(A)—we see them asking for that, and when they start demanding
it, then we'll really see some results.”
86
Enclosure Types
[TMEIC]
• ODP
•
•
[Alibaba]
Open Drip Proof
Well-ventilated rooms
• WPII
•
•
•
Weather Protected Type II
Open-outdoor type
Inlet air travels through
three 90 degree turns
[Marathon]
• TEFC
•
•
7
Totally Enclosed Fan Cooled
Environments containing
corrosive or harmful gas
[RMS]
NAE Workshop on Progress
of Noise Control
Figure 3.7-1 Common motor enclosures.
Industry Standards -IEC 60034-9:2003
[IEC, 2003]
•
•
•
Rotating electrical machines - Part 9: Noise limits
Limits sound power level as a function of HP,
speed, enclosure type, and cooling
For example:
•
•
•
•
10
5000 HP motor
1800 RPM
TEFC, cooling air from shaft-mounted fan
Max Lw permissible – 115 dBA
of Noise Control
Figure 3.7-2 One IEC industry standard.
87
Lw of 3600 rpm vs HP &
Enclosure Type
20
[Toliyat, 2004]
of Noise Control
Figure 3.7-3 Noise level by enclosure type.
Comparison: Frame Design
[Toliyat, 2004]
21
of Noise Control
Figure 3.7-4 Noise level by frame design.
88
Quieter Fan, con’t
[Judd]
[Judd, 1969]
29
of Noise Control
Figure 3.7-5 Noise level comparison: nondirectional vs. unidirectional fan.
Reducing Magnetic Noise
[Vijayraghaven; Curiac; Goss]
• Enlarge the rotor/stator airgap - reduces the flux density
• Skew the stator or rotor slots in small motors
• Careful stator/rotor
mechanical design
• Adjusting stator/rotor slot
dimension and number
• Parallel paths in stator
windings
32
of Noise Control
Figure 3.7-6 Magnetic noise reduction strategies.
89
Comparison: Large Pumps Driven by
Air-Cooled vs. Water-Cooled Motors
[CSTI]
• Measurements made of numerous pumps
• Multiple test conditions
Test
Condition
35
Range of Noise Levels, dBA
Air-Cooled
Water-Cooled
Difference,
dBA
Low Pressure,
Low Speed
82 - 91
79 - 87
3–4
High Pressure,
High Speed
89 - 97
87 - 94
2–3
of Noise Control
Figure 3.7-7 Air-cooled vs. water-cooled motors.
90
3.8 COMPRESSOR NOISE
Michael Lucas - Ingersoll Rand, Inc.
Ingersoll Rand is an example of a company that has invested in noise abatement—in the case
relevant to this paper, reduction in noise from air compressors. The company's areas of focus
have included homing in on the best standards for noise measurement and designing quieter
products that meet consumer demands.
Michael Lucas, with Ingersoll Rand in Davidson, NC, spoke about progress made in reducing
noise levels from air compressors during the 16-year period he has worked for this company. In
particular, he spoke about progress in reducing compressor noise; types of engineering noise
abatements that have succeeded; and the role of technology in engineering noise control.
Air compressors are used in many areas, including in trucks transporting powdered
goods; in the oil and gas industries; in road construction; and in chemical plants for
manufacturing pharmaceuticals. Ingersoll Rand has worked to achieve noise levels that the
company believed consumers would find acceptable. While the Compressed Air Gas Institute's
CAGI PNEUROP S5.1 was once the standard for its air compressor testing and certification,
Ingersoll Rand began a transition around the year 2000 from CAGI to European ISO codes.
Essentially, this involved moving from a four-microphone test to a more stringent test under the
guidance of ISO 3744 or the two acoustic intensity standards 9614-1 and -2.
As illustrated in Figure 3.8-1, Ingersoll Rand provides its preliminary design groups with
documents containing relevant specifications. In this case, the company conveyed the range of
noise levels from the relevant design specification based on various operating conditions.
Lucas found that, with the new standard and a heightened interest in reducing noise, noise
levels have decreased industry-wide by 3 to 5 dB(A) and sometimes more. Types of successful
noise abatement methods include package cooling; pulsation dampeners and silencers; and
isolation mounts.
Before 2000, Ingersoll Rand achieved package cooling with propeller fans, which are
inexpensive and easy to source around the world. But propeller fans were falling far short for
package cooling, and in particular for noise. Problems included inadequate cooling, blades that
fluttered and broke, and fan motors that were burning out. After convincing product development
teams of the benefits of backward curve blowers, these increasingly replaced propeller fans.
Blowers were three to four times more expensive, but resulted in better reliability and fewer
failures in the field, along with reduction in noise. As illustrated in Figure 3.8-2, a dramatic
decrease in sound level is achieved by increasing static pressure and moving into the ideal range
of specific speed.
Figure 3.8-3 shows the type of backward curve blowers replacing propeller fans for
cooling a compressor package. The large blowers rely on six-pole motors running at lower speed
compared to the traditional fans with less costly four- or two-pole motors.
Ingersoll Rand relies on modern modeling tools to change its designs in keeping with the
introduction of new generations of compressors. Around the year 2000, the company switched its
silencer technology for reducing pressure pulsation. The change was made from venturi silencers
to advanced pressure pulsation devices, thanks to the introduction of computational fluid
dynamics (CFD) and acoustical finite element analysis/boundary element analysis (FEA/BEA)
models.
91
In designing a silencer, Lucas said, he strives to address 95 percent of the noise problems
occurring in the field. For the rest, specialized silencers are installed in the field that meet a
customer's specific needs based on acoustic resonances in the piping.
Lucas next discussed isolation mounts for noise abatement on an Ingersoll Rand
PETStar® project he worked on in 2015. The project supported a switch from the industry
practice of epoxy grouting the compressor frame to the factory floor to floating the machine on
pneumatic mounts, as shown in Figure 3.8-4. In addition to significantly reducing noise and
vibration, the change saved Ingersoll Rand millions of dollars.
The presenter moved next to a discussion of the role technology plays in engineering
noise control. First, he discussed the draft standard ISO 7849 on estimating sound emissions
from vibration measurements. Traditionally, sound intensity is used when trying to measure
sound power, but Lucas found that applying accelerometers to measure structure-borne sound
power levels can be equally useful and sometimes more accurate. He follows the draft ISO 7849
which, though never finalized, is highly effective for centrifugal, reciprocating, and screw
compressors, where most noise is structure-radiated noise. Figure 3.8-5 illustrates a comparison
of noise levels recorded for three screw compressor models using ISO 7849 (labeled “overall
measured levels using SAM”) and using the traditional microphone method based on ISO 2151,
which is a derivative of ISO-3744).
Ingersoll Rand also uses a technique called acoustic holography, in which a holography
system built in-house scans a compressor using a horizontal traversing mechanism. The
technique has been used to solve difficult noise and vibration problems.
Another tool the company uses to design low-noise compressor products is computational
fluid dynamics. Ingersoll Rand has invested significant financial resources in expanding this
CFD capability, and the presenter himself spent the last five years working on CFD and a related
field called “moving mesh.” In moving mesh, the movement of turbomachinery components is
simulated by moving the mesh representing the flow domain. CFD's availability to engineers can
be expected to broaden as cost decreases and computer speed increases.
The presenter next addressed the challenges associated with a variable speed drive, or
variable frequency drive (VFD). VFD is now available for most compressors, and its energy
savings can justify the extra cost of the drive. From a noise control engineering perspective, he
said, VFD is a problem when there are structural or fluid dynamic resonance instabilities. In
some products' speed ranges, a VFD can excite resonances and in turn cause significant noise
and vibration problems. Strategies for addressing these challenges include improved predictive
modeling; silencers; structural ribs or changes to housing casting; welded flanges or braces; and
sometimes, as a last resort, using skip speeds. There is a need for better methodologies for
predicting these problems and finding ways to eliminate resonances when they occur.
The presenter next discussed a challenge his company is currently addressing, illustrated
in Figure 3.8-6. The compressor shown (gearbox, electric motor, and fan) once operated at a
single fixed drive speed. The new product's variable speed drive operates over a continuous
range of drive speeds. As a result, the combination of pressure pulsation of the compressor, the
gear meshing frequency in the gear box, and the bending modes of the drive motor shaft can
become excited at different drive speeds. Structural resonances are excited that then cause noise
and vibration problems.
Lucas concluded by speaking about the customer-driven nature of noise level reduction
and advances made to meet those demands. Customers have desired lower-noise compressors for
health and safety reasons, and meanwhile better standards have been developed to more
92
accurately report product noise levels. In terms of translating technological progress into real life
improvements, Lucas himself has devoted time to educating and developing product teams,
which he says “are now knowledgeable on how to design low-noise products.”
Tabulated Example
Range of compressor operating conditions
Overall noise levels on average Have decreased 3 to 5 dBA
over the past decade
Figure 3.8-1 Sample design specifications.
93
5
Noise Improves with cooler
100
Sound Pressure Level, dB
Blue - No Honeycomb
Red - With Honeycomb
90
80
70
60
50
0
1000
2000
3000
4000
5000
6000
7000
Frequency, 1/sec
Pressure drop improves
blower performance and noise
8
Figure 3.8-2 Sound level reduction achieved by blower.
6 pole motor – 20,000 cfm
9
Figure 3.8-3 Backward curve blowers replacing propeller fans.
94
Float entire machine on pneumatic mounts
(Today)
13
Figure 3.8-4 Pneumatic mounts, an improvement over epoxy grouting.
Comparison between noise levels determined
using vibration (ISO 7849) and pressure
measurements (ISO 2151 & ISO 3744).
Side 3
Side 2
73
64
64
56
55
62
62
66
64
57
62
63
62
63
57
16
Figure 3.8-5 Noise level comparisons for two measurement methods.
95
Future Challenges – Variable Speed Drives
19
Figure 3.8-6 Variable speed drives introduce new noise issues.
96
3.9 POWER AND DISTRIBUTION TRANSFORMER NOISE
Ramsis Girgis—ABB Inc.
Mats S. Bernesjo – ABB Inc.
Modern methods for controlling transformer noise can minimize disturbance to neighbors. With
a significant R&D effort and investment, ABB developed, designed, and delivered ultra-low
noise transformers for Consolidated Edison (ConEd) in Manhattan that don't rely on sound
enclosures or panels and that have come to represent a global gold standard in the field. This
ultra-low-noise transformer technology is now being used by ABB Power Transformer factories
around the world to produce low-noise transformers for other metropolitan areas around the
world.
Ramsis Girgis spoke about power and distribution transformer noise on behalf of himself and
presentation co-author Mats Bernesjo. Both have worked in this area for many years as part of a
global ABB team. Low-noise transformers are needed, Girgis explained, because people living
near substations are otherwise subjected to “annoying” tonal noise. “Nobody wants to hear
transformer noise when they're trying to go to sleep.”
Girgis introduced the basics of transformer construction, as depicted in Figure 3.9-1.
Transformers shown include the most common type—a three-phase transformer with the
windings wound around the core's three limbs—as well as a small dry-type transformer like the
ones used inside buildings; a large power transformer, with its core made of sheets of electrical
steel and three limbs with yokes and clamps; and a distribution-size transformer with the same
type of construction.
The three components of transformer noise, based on their source, are core noise; cooling
equipment noise (from fans and pumps); and load noise (from windings and tank). The first type,
core noise, is generated because the core of the transformer is made of electrical steel
laminations that elongate and contract with increases and decreases in magnetic flux,
respectively. Girgis presented the typical frequency spectrum of core noise, shown in Figure 3.92. With a high flux density, components can include 480 Hz and higher, all tonal, he said. Also,
core resonance frequencies in close vicinity to any of the exciting frequencies of the transformer
can magnify a frequency component of the core noise by as much as 10 dB and the total core
noise by as much as 5 dB.
Cooling noise from fans and pumps creates both low-frequency and mid-frequency noise,
as shown in Figure 3.9-3. However, overall noise from these sources is mostly broadband and
typically is not as bothersome as tonal noise, Girgis stated. The relatively low frequency of the
fan blade passing noise contributes relatively little to the total transformer noise. But the higherfrequency broadband fan noise does contribute significantly to the total transformer noise when
high noise fans are operating.
Load noise—which is mostly, or entirely, 120 Hz (for a 60 Hz transformer)—is produced
by the transformer's windings and tank vibrations. More specifically, the noise is caused by
magnetic leakage flux from current flowing in the windings, which creates electromagnetic
forces that cause the windings to vibrate; and also from leakage flux impinging on the tank walls
causing the tank to vibrate due to magnetic pull forces. A typical load noise frequency spectrum
is shown in Figure 3.9-4.
97
To reduce transformer noise, manufacturers use HI-B electrical steel with high grain
orientation rather than the regular grain-orientation steel used by transformer manufacturers
decades ago. They also use step-lap joints in the core for a better flux distribution at the corners
of the core. While lower operating flux density is an option for reducing noise, this approach
creates not only a higher cost, but a bigger core whose dimensions and weight can make
transporting the transformer difficult.
Girgis spoke next about optimizing the design margin. With significant competition today
in terms of lower prices, liberal margins on the transformer's design are less of an option. Noise
level design margins today need to be in the 2 or 3 dB range, he explained, which requires a very
accurate calculation of noise level, including core and tank resonance frequencies. Vibration and
sound transmission must be minimized; for example, the transmission of the vibrations from the
core and coils to the tank needs to be minimized.
To manage cooling system noise, manufacturers use low-speed, low-noise fans; lownoise pumps; and ultra-low-noise fans with sound-absorptive shrouds. In more extreme cases,
fans are not even used.
To lower load noise, transformers are designed based on rigorous calculations and
modeling that involve relevant design parameters. Winding mechanical resonance is avoided,
and appropriate magnetic or conductive shielding is used inside the transformer tank.
To reduce both core and load noise, transformers are designed to reduce the tank’s
vibrations and sound radiation by properly dimensioning the tanks themselves, and the tank
stiffeners. Tank sound panels and sound enclosures are sometimes used, as well, but they are
more effective for higher frequencies and therefore less effective for reducing load noise.
Additionally, sound enclosures are very expensive, especially for load noise reduction, so
designing a lower-noise transformer can be the more cost-effective choice.
Girgis spoke next about a major ABB project for ConEd in New York City that kicked
off in 2004. This major energy utility needed ultra-low noise large transformers that would be
installed in close vicinity to extremely expensive Manhattan high-rise apartment buildings. The
company requested transformers with noise levels more than 20 dB lower than typical levels at
voltage over-excitation and full load, and they asked for guarantees on the levels at each main
frequency component of the transformer noise. Other “very tough” requirements for the
manufacturer included strict limitations on the width, height, and weight of the transformers to
allow them to be transported on Manhattan roads and bridges, and under overpasses.
Rigorous R&D was required to meet these varied requirements, resulting in three
generations of low-noise transformers as shown in Figure 3.9-5. The first of the ABBmanufactured ConEd transformers was produced in 2004 with a sound enclosure. After testing
the transformer with the enclosure to ensure it satisfied ConEd's noise level requirements, the
enclosure had to be removed for transportation and then installed again on-site once the
transformer was installed in the field.
Two second-generation transformers were developed the next year. This time, only sound
panels were used that cost significantly less than the sound enclosure, In addition to being less
expensive, the sound panels were also easier to install and could be transported along with the
transformer.
The last set of transformers in this series was produced in 2008 and 2009. Girgis stated
that the Generation 3 transformer became ABB’s low-noise transformer technology, used by
ABB designers worldwide to produce such transformers for other metropolitan areas. The ultralow-noise transformer technology does not use sound enclosures or sound panels and has
98
achieved the lowest noise level yet, along with significant savings in the weight and size of the
core and windings. “That's what doing rigorous development work produces,” the speaker said.
Girgis then explained why low-noise transformers are preferable to alternatives such as
using sound enclosures or sound walls: Sound walls are less effective at long distances from the
transformer, where residences are located; require more real estate; are more likely to catch fire;
and are not economical. Also, sound enclosures are inconvenient for maintenance and generally
hinder cooling efficiency. Girgis added that quiet transformers are perceived to be of higher
quality.
The presenter concluded with examples of future needs in this context: developing lower
magnetostriction core steels; examining interior noise reduction approaches; and using more
effective bracing of windings, improved modeling techniques, and improved transformer
mounting on-site.
In response to a question about whether trade-offs exist in terms of noise reduction and
electrical performance, Girgis stated that reducing noise levels while still satisfying electrical and
other requirements, and also controlling costs, is a challenge that requires tremendous expertise
in transformer design. It is important for both the transformer manufacturing industry and
electrical utility companies to generate interest in acquiring this expertise, he said. Finally, Girgis
concurred with a comment that energy-efficient transformers can not only perform efficiently,
but can also operate more quietly.
Construction of a Transformer
© ABB
May 8, 2016
| Slide 5
Figure 3.9-1 Transformer construction.
99
Core noise
Caused by Magnetostriction of Electrical steel

120 / 240 / 360 / 480 Hz depending on core material and level of core flux density

Core resonance magnifies one or more components by as much as 10 dB
Sound Pressure level, dB (A)
50
40
30
20
10
0
80 100 125 160 200 250 315 400 500 630 800 1000
Frequency, Hz
© ABB
May 8, 2016
| Slide 8
Figure 3.9-2 Core noise—typical frequency spectrum.
Cooling equipment noise
Caused by fans and pumps

Moderate low – frequency (40 – 80 Hz) fan – blade noise
 Pumps / motor noise => Higher – frequency components
 Remainder is wide – band noise => High dB (A)
80
dB (A)
Sound Pressure level
70
dB
60
50
40
30
20
10
0
25 31.5 40
50
63
80 100 125 160 200 250 315 400 500 630 800 1000
Frequency, Hz
© ABB
| Slide 9
Figure 3.9-3 Cooling noise—typical frequency spectrum.
100
Load noise
 Caused by leakage flux
 Produced by vibrations of the windings & tank walls
 Mainly 120 Hz
Sound Pressure level, dB (A)
70
60
50
40
30
20
10
0
80
100
125
160
200
250 315 400
Frequency, Hz
500
630
800
1000
© ABB
| Slide 10
Figure 3.9-4 Load noise—typical frequency spectrum.
Result of development effort – 3 design generations
Generation # 2
Generation # 3
w / Sound Enclosure
w/ Sound Panels only
No sound panels
(2004)
(2005)
(2008)
Generation # 1
3.7 dB lower Core noise
9.2 dB lower Load noise
10 % less core weight
16 % less winding weight
© ABB
| Slide 18
Figure 3.9-5 Three generations of transformer noise control design.
101
3.10 ENGINEERING QUIETER VALVES AND PIPING SYSTEMS
Allen C. Fagerlund (first author) - Fisher Controls International
Eric W. Wood (presenting) - Acentech Incorporated
More and more, plant owners are considering noise levels when designing their facilities' valves
and piping systems. In consideration of employees' health and safety and neighbors' desire for
quiet—as well as a self-interest in systems that hold up—plants are being planned with modern
valves and piping systems that decrease noise while also improving system dependability.
Eric Wood, with Acentech, presented a paper focusing on valves and piping systems on behalf of
himself and first author Allen Fagerlund, with Fisher Controls. By way of introducing Fagerlund,
Wood stated that his co-author has expertise in computational modeling, physical testing, and
evaluation and control of noise from valves and piping systems.
Wood first summed up the function and structure of valves, which control pressure or the
flow rate of a gas or a liquid flowing in a piping system. Inlet diameters range from very large—
sometimes more than a meter—to only 5 centimeters or less in life science applications. For
information about valves and piping systems, the presenter recommended the Emerson “Control
Valve Handbook,” available for free download on the company's website:
http://www.documentation.emersonprocess.com/groups/public/documents/book/cvh99.pdf
If a valve and piping system with liquid flowing through it is causing excessive noise,
Wood explained, it is generally not normal but due to cavitation, which means the pressure
downstream of the valve is below the vapor pressure of the liquid, and bubbles are forming.
Noise is a symptom, but cavitation indicates the wrong valve is being used and the system may
sustain damage.
Wood turned next to the main focus of his presentation: valves and piping systems with
gas flows. With high flow rates and high pressure drops, noise radiates from upstream piping, the
control valve and the valve's attached control instruments, as well as from downstream piping or
an atmospheric vent.
Decades ago, noise in piping systems was not a consideration when designing a new
refinery, power plant, or industrial facility, Wood pointed out. “The buyer didn't care. The
manufacturer didn't care.” But today plant owners expect lower noise levels for various reasons,
including protecting the safety and health of the plant's employees; avoiding unnecessary
disturbance of residential neighbors; and preventing vibration-induced failures in the valves and
piping systems. Stressing a theme that he said Fagerlund also champions, Wood said, “Lower
noise is a good investment, not just an expense.”
Fagerlund and other engineers are performing computational and physical testing and
evaluations to develop low-noise piping and valve systems across manufacturers and industries.
Today control valves are readily available for even very severe flow conditions that produce 10
to 40 dB(A) less noise than earlier designs.
The extent of noise generation is related to the type and temperature of the fluids that are
flowing, the mass flow rates, upstream and downstream pressures, piping schedules and
diameters, obstructions within the piping, and perhaps most importantly, valve trim
configurations.
102
Wood and Fagerlund tend to divide noise reduction into two different components: path
treatments (reducing the noise radiating from the piping system—that is, after the noise is
generated) and source treatments. Path treatments to reduce noise radiation include heavier wall
piping and external lagging with a fibrous insulation covered with metal jackets.
Next, Wood discussed colleague Fagerlund's example piping schedule and path
treatments, without source noise control, as shown in Figure 3.10-1. Schedule 40 piping1 resulted
in 110 dB outside. With a heavier, Schedule 80 piping, noise dropped to about 102 dB. With
Schedule 40 piping and insulation and jacketing, radiated noise level dropped to about 95 dB.
After the insulation and jacketing was removed from the Schedule 40 piping, the noise returned
to about 110 dB.
Figure 3.10-2 illustrates a control valve with a sparger, or diffuser, installed downstream.
This relatively simply installed system increases back pressure on the valve, and reduces noise
generation and noise radiation.
For atmospheric vents downstream of the control valve, the piping releases steam or gas
to the atmosphere. High flow rates, with noise levels as high as 110 dB(A) at 90 meters, can be
objectionable to neighbors. Outlet mufflers can reduce this noise by at least 20 and even 30
dB(A). At Fisher, Fagerlund tests how to quiet noise from atmospheric vents.
Many manufacturing facilities use air compressors with small, high-pressure jets to
perform tasks such as moving, cooling, or cleaning parts along an assembly line. Reduced-noise
nozzles, mufflers, and diffusers are readily available to reduce noise by 10 to 20 dB(A).
Modern valves have been designed with special low-noise trims that contain many small
pathways through which air or gas travels. Examples are shown in Figure 3.10-3. The small fluid
passages provide favorable velocity and frequency spectra that reduce noise by as much as 30 to
40 dB(A) compared with standard trims.
Wood next turned to the inside of a pipe. Noise levels inside the piping with gas flow,
downstream of a standard control valve, can reach 150 dB and higher. Figure 3.10-4 shows
representative internal noise levels downstream of a standard and low-noise valve, using
calculation routines provided in IEC 60534-8-3. Frequency band sound pressure levels exceed
150 dB with a standard valve, and are reduced by 10 to 30 dB with the lower-noise valve. Figure
3.10-5 shows external sound pressure levels associated with a standard and lower-noise valve,
about 1 meter from the piping system, using the same IEC standard.
Wood next moved the discussion from the lab context to the real world. He said that “the
noise from valve and piping systems really matters for the people that work in the plant 8, 10, 12
hours a day, and also the residential neighbors.” People expect progressively lower noise levels,
while service conditions (pressure, flow, temperature) are rising. Fagerlund and other noise
control engineers are making progress, however. Their computer systems are increasingly
sophisticated, computational power is rapidly increasing, and new physical modeling data help in
the design of lower-noise systems.
Advances are being made, and will continue into the future, in the extraordinarily
complex area of making internal measurements of the spectral characteristics of sources
associated with the control valve inside of piping systems. And, as field conditions change,
testing will occur under conditions of higher pressure and higher temperatures. There will be
improvements in approaches for predicting or measuring the internal sound field; improved
1
Pipe schedule refers to pipe wall thickness for a range of pipe diameters. Pipe schedule tables are
available online.
103
understanding of how the internal sound field couples with the pipe walls; and a better
comprehension of the turbulence within the system.
In conclusion, Wood stated that U.S. engineers such as the workshop's attendees are
continually contributing to the design and development of quieter products for the global market.
Path treatments without source noise control
Engineering Quieter Valves and Piping Systems
Figure 3.10-1 Path treatments and noise (no source noise control).
104
Installation of a sparger (diffuser) downstream of
a valve increases backpressure and reduces
noise generation and radiation
Figure 3.10-2 Control valve with a sparger downstream to reduce noise.
.
Examples of low noise valve trims and cages.
Figure 6. Examples of low noise valve trim and cage
Figure 3.10-3 Examples of modern valves with low-noise trims.
105
Internal Sound Level Lpi (dB)
180
170
160
150
140
130
120
110
100
Lpi standard
90
Lpi low noise
80
10
100
1,000
10,000
Frequency (Hz)
Representative
internal sound pressure levels
Internal sound pressure levels (Lpi) for standard and low noise valves
downstream of a standard and a low-noise valve
A-weighted External Sound Level Lpe (dBA)
Figure 3.10-4 Internal noise levels downstream: standard versus low-noise valve.
120
110
100
90
80
70
60
50
40
Lpe standard
30
Lpe low noise
20
10
100
1,000
Frequency (Hz)
10,000
Representative
external sound pressure levels 1m
Figure 7b. External sound pressure levels (Lpe) for standard and low noise valves
downstream of standard and low-noise valves
Figure 3.10-5 External noise levels downstream: standard versus low-noise valve.
106
3.11 NOISE FROM GEAR DRIVES
Rajendra Singh - The Ohio State University
Given that gears are used to adjust speed and transmit power, their whine and rattle noise may
never be eliminated altogether. Still, efforts to improve gear and system design—and associated
manufacturing methods, as well—exhibit promise to achieve meaningful inroads in gear noise
abatement.
The Ohio State University's Raj Singh spoke about gear-associated noise issues. Gears are a $50
billion industry globally, with applications ranging from the transportation arena (automobiles,
off-road vehicles, helicopters, and submarines, for example) to industrial equipment (including
construction machinery, power plants, wind turbines, and automation actuators) to consumer
products (such as tools, hair clippers, toys, and even baby swings).
Gears will never be silent, Singh said, given their primary function of transmitting power.
About a decade ago, the American Society of Mechanical Engineers (ASME), in collaboration
with organizations such as General Motors, Boeing, and the U.S. Army, developed a 20-year
vision that included the goal of reducing gear noise while increasing speed and power.
The two major types of gear noise problems, as summarized in Figure 3.11-1, are
whine—the primary focus of Singh's presentation—and rattle. Gear noise is generally a function
of load and speed, and quieting gear whine noise becomes more difficult as the range of power
density increases. Conversely, rattle noise (generating vibro-impacts) is associated with very
light loads and clearances. Mechanical design and tooth modification are closely associated with
gear noise reduction, as is the manufacturing process. Very few gears have been designed and
manufactured to be ultra-quiet, Singh said.
The speaker next discussed the example of a simple gear pair. Looking at sources, mainly
vibrational sources (or mechanical sources) are seen at the gears' interface. The transmission
error is a deviation from the kinematic conjugacy2 of the order of a micron, which can create
significant noise. Given a one micron displacement amplitude at 1000 Hz, an almost 100 dB
noise level may be generated with perfect sound radiation surfaces.
In high-precision machinery, Singh pointed out, micron level accuracy is relevant in
terms of manufacturing errors and elastic deflections. Gear whine noise at mesh frequencies is
primarily a structure-borne path involving the gear bodies, the shaft, the bearings, the casings,
and the mounts, which affect gear noise by amplification and diffusion of energy throughout the
system. Ultimately, at the receiver, significant noise is observed at the gear mesh frequencies and
associated sidebands.
Some fundamental academic lessons about vibration isolation may not apply, Singh said,
because compliant bearing caps, flexible casings, and ill-designed shafts and bearings might
actually enhance motions or forces at the source. A geared system can be highly nonlinear with
significant interactions taking place within it.
Given a simple gear pair, the presenter said, a system-oriented model can go from the
gear sources to sound pressure. For example, contact mechanics codes can be used to help
identify sources in terms of transmission error, mesh stiffness variation, and sliding friction.
2
A list of gear nomenclature is provided at:
https://en.wikipedia.org/wiki/List_of_gear_nomenclature
107
A calculation code can provide the internal gear mesh and bearing forces, and then forces
or motions can be transmitted to the casing; bearing transfer properties are relevant in this regard.
Usually, the bearings are rolling element types, except in some cases of heavy equipment with a
hydrodynamic bearing or similar mechanism. Casing dynamics and mount properties are also
relevant for predicting sound pressure for a geared system. With respect to planetary gears or a
multi-mesh geared system, it can be more challenging to develop a mathematical model, given
multiple sources, paths, and other interactions.
Singh next spoke about NASA gear pairs—gears designed for research and experimental
work for helicopter transmission design. Figure 3.11-2 shows shaft displacements, in the line of
action (LOA) and off line of action (OLOA), as a function of torque. The gears are designed to
be quiet in terms of the transmission error, at the design load of 600-pound-inch torque, for
example, and the vibration level is relatively minimal. This assumes only one source
(transmission error), however. But when this source is minimized, other noise sources such as
the sliding friction arise. With vibration sources and paths well defined, determination of sound
radiation becomes easier.
Sound pressure level for any gear pair is a function of torque. As multiple sources start to
enter, the dip in the vibratory displacement vs. torque is usually not visible in terms of the noise
vs. torque curve.
Gear design is vital—for example, going from spur gears to helical gears and considering
the high-contact ratio gears. And micro-geometry modifications (in terms of the profile and lead)
may be the most important factors. For instance, profile modifications such as tip relief can be a
tremendous help in gear design. So when someone wants quieter gears designed, Singh said,
fundamental design and gear contact patterns are among the factors considered.
Manufacturing restrictions can make some designs impossible to achieve and some error
inevitable. Engineers may have little influence on the manufacturing side, Singh said, but the
introduction of a quieter design—even where significant resonances and dynamic interactions
within the system render conventional vibration control solutions useless—represents the “holy
grail” design.
Singh spoke next about gear rattle, which is compared with gear whine in Figure 3.11-3.
Unlike gear whine, rattle issues assume intermittent contacts and tooth separations, resulting in
the generation of periodic impulses entering under some external vibration source. Rattle
problems are more system-oriented than whine. Figure 3.11-4 shows the types of impacts based
on mean and dynamic loads, and Figure 3.11-5 depicts the role of backlash within a system: Too
little backlash could create a whine problem, while too much would induce rattle.
Singh moved next to trends in automotive transmission designs. Changes to fuel
economy over the last 40 years, he said, are directly associated with rattle problems in the U.S.
and around the world. Changes contributing to increased vehicle rattle include: decreases in
cylinder number; turbocharging; the use of diesel rather than gasoline; reduced flywheel inertia;
synthetic lubricants; the addition of transmission speeds; and high torsional system loads.
Turning to the subject of education, the presenter stated that gears receive only a brief
mention in undergraduate machine design courses. And when they are covered, involute gear
design is the focus, when in actuality it is impossible to produce a perfect involute and every gear
has various errors. In graduate education, few institutions address this topic, especially in the
context of noise and dynamics.
As for research, investigation in this area is rarely funded by government agencies and
other large research sponsors. And only two national laboratories are conducting research in this
108
field: NASA Glenn, which focuses on aerospace and helicopters, and the National Renewable
Energy Laboratory (NREL), which concentrates on wind turbines.
Future research should investigate many fundamental issues, given the complexity of
high-speed machines; the extensive nonlinearities in these types of physical systems; and time
and spatial variations of contact parameters involved. To achieve quieter products,
manufacturing improvements are also critical.
Increasing power density and a rising variety of products, along with problems in
manufacturing, require attention. Limited calculation capabilities and inadequate time allotted to
experts to solve complex problems in this field are additional challenges. While additional
knowledge must be generated, design guidelines (especially in the context of noise control) must
also be better disseminated, Singh emphasized. The Ohio State University is one institution that
has been teaching a short course in the area. More than 1,900 engineers (from over 350
companies) have taken the class over 36 years, and it is clear that the 50 or so students (from
industry) in each class are usually eager to learn about various aspects of gear noise.
Two Major Gear Noise Problems
Type
Nature (depends on geared system design, mean load,
speed, dynamic load, etc.)
Whine
Steady state noise at gear mesh frequencies and sidebands
Rattle
Backlash-induced periodic impulsive noise (vibroimpacts) under lighter loads
Gear Noise
NAE Workshop
Raj Singh, Oct. 2015
Figure 3.11-1 Gear noise: whine versus rattle.
109
3
Validation of Gear Noise Source Model (with NASA Spur
Gear Pair)
OLOA Displacement
LOA Displacement
100
Normalized Yp
Normalized Xp
Normalization
reference point
80
80
Mesh order: m = 1
40
m=2
60
40
20
m=3
0
0
500
600
700
800
500
900
600
700
800
900
Torque (lb-in)
Torque (lb-in)
Measurement: discrete points
Prediction: lines
Friction effects dominate the dynamics at “optimal” load
Gear Noise
NAE Workshop
7
Figure 3.11-2 Gear noise validation: shaft displacements vs. torque.
Whine vs. Rattle
Whine
Nature
Rattle
Backlash- induced vibroSteady state vibrations of
impacts and tooth
an elastic gear pair
separation
Analysis Domain
Frequency (modulated
pure tones)
Time (cyclic transients)
Excitation
 Internal (gear mesh
frequency regime)
 External (low
frequency dynamics)
External (torque
pulsation)
Mean Torque Load At all loads
Gear Noise
None to low
NAE Workshop
Figure 3.11-3 Comparing gear whine and rattle.
110
10
Vibro-Impacts Impacts Based on Mean & Dynamic Loads
F
F
x
x
No Impact
Single Sided
Impact
F
F
x
x
Double Sided
Impact
Gear Noise
Rapid Changes
in Mean Load
NAE Workshop
11
Figure 3.11-4 Vibro-impacts based on mean and dynamic loads, given backlash.
Role of Backlash on Rattle (and Whine)
F
whine
ΔL
(dB)
Rattle
Rattle reduced
with excessive
backlash (single
sided impact)
x
0-14 dB
Single Sided
Impact
3-5 dB
Backlash
 Backlash is desired for assembly and lubrication
 Rattle reduction concepts
• Control / minimize backlash
• Increase the mean load
• Reduce the dynamic load
• Use anti-backlash gears (if possible)
• Employ system design concepts (eigenvalue placements, isolation, etc.)
Gear Noise
NAE Workshop
12
Figure 3.11-5 Effects of backlash on noise and some concepts to reduce gear rattle.
111
3.12 Engineering Quieter Off-road Machines
Karl B. Washburn - RSG
Eric W. Wood - Acentech
Once, the attitude in the off-road machines industry was “the more noise it made, the better.”
But regulation such as the EU Noise Directive, new technologies, and market pressures have
helped make quieter off-road machines a reality.
From his perspective as a former John Deere staff engineer, Karl Washburn presented
information about noise from off-road machines. Washburn, currently a senior acoustics
consultant with RSG, started by clarifying that an “off-road machine” is a machine that does
work of some kind (rather than transporting people or goods): earth moving, mining, quarrying,
construction, demolition, road building, agriculture, grounds care, etc. These mobile machines
are becoming “factories on wheels,” Washburn said. Their power and weight range broadly, yet
tremendous overlap exists in noise-related and other challenges across the many machine forms.
Off-road machines are all about functionality, Washburn said, meant to perform their
tasks efficiently, quickly, and at the lowest possible cost. Historically, the presenter summed up,
“Noise was perceived as power. If you couldn't hear it, it wasn't doing the job.” Safety and
comfort—and therefore noise reduction—were secondary when it came to off-road machines
such as those shown in Figure 3.12-1. “No one cared how much noise it made and, to some
extent, the more noise it made, the better,” Washburn said, and these priorities resulted in many
workers in the industry suffering significant hearing deficit over the course of their careers. But
there has been a generational shift in this attitude.
As background, Washburn summarized the machine characteristics creating noise
historically, as illustrated in Figure 3.12-2: bare, exposed operator stations; unmuffled or poorly
muffled exhaust systems; open engine compartments; and inexpensive stamped steel paddle fans
for cooling, spinning constantly at full speed.
Today, off-road machines still have inherent characteristics that contribute to noise,
including: their engines (primarily diesel engines that achieve high torque at low speed);
hydraulics for work functions and for propulsion; cooling systems that are the predominant
sources of radiated noise; drivetrains; and cabs with powerful HVAC blowers. Also, sometimes
the work itself creates noise (for example, the gravel-steel interaction during dumping into a haul
truck’s bed, or noise generated by demolition tools attached to excavators). Many of these
sources are illustrated in Figure 3.12-3
For modern machines such as those shown in Figure 3.12-4, significant noise reductions
have been achieved over the last 15 years, thanks to (1) regulation; (2) advancing technologies;
and (3) market pressures.
Regulation
The EU Outdoor Equipment Noise Directive 2000/14/EC achieved significant noise
reduction across various machine forms, Washburn said, and “was an enormous shot across the
bow” in the off-road machinery industry. As off-road machines were being manufactured with
increasing power levels (in keeping with customers' desires), they were getting progressively
noisier. The EU Noise Directive turned that trend around.
112
Basically, its first phase set a limit for the emitted sound power level for each type of
machinery, and the limit increased as a function of engine power (based on 11 times the log of
the engine power in kilowatts). This stage took effect in 2002. The Directive's second stage,
which took effect in 2006, lowered the baseline sound power levels for all equipment by an
additional 3 dB(A).
This Directive (which was followed by similarly strict regulations in Japan and China)
was by far the largest single driver of lower noise emissions. Rather than making different
versions of each machine for different markets, manufacturers often made changes across the
board, thus achieving noise reductions in the U.S., as well.
Advancing Technologies
Installing efficient technologies—such as a high-efficiency fan running at a slower speed
compared to an inefficient one—can save a tremendous amount of fuel. In turn, the fuel savings
can attract customers to a manufacturer's product with the slower fan that is also much quieter. In
this way, the technology of improving fuel economy led, secondarily, to noise reductions.
The U.S. EPA "Tier 4" diesel engine exhaust gas emission requirements have been a
game changer. The requirements for reduced emissions led manufacturers toward integrating
engine, fuel, and exhaust controls as a system. The introduction of selective catalytic reduction
and diesel particulate filtration has eliminated the “bark and roar” of diesel engines. Along with
these advances came new challenges for noise: The new technology significantly increases heat
load, requiring a return to faster fans, and higher compression ratios can increase engine noise.
Washburn: “The point is, the technology was driving the noise reduction. The noise reduction
was not driving the technology.”
Market Pressures
Enormous monetary investment has been made in the U.S. in the last decade toward
reducing off-road machinery noise. Washburn pointed to what he called the “Ford F-150
effect”—referring to the quiet interior that some cars offer drivers—as an example of
manufacturers attracting customers by providing a more pleasant operating environment. Even
smaller manufacturers have sometimes been able to offer a quieter cab as a leg up on their larger
competitors.
With market expectations as one driver, important strides have been made since the year
2000. For example, some motor graders and four-wheel drive loaders have gotten more powerful
by about 15 percent, while noise has been reduced by 10 dB(A) within a decade's time. The
machines are putting out about one-tenth of the sound energy compared to a decade ago.
Some machines are now available with in-cab noise levels of 70 dB(A) or lower, a
significant achievement by the manufacturer’s noise control engineers. Noise reduction is
winning the attention of product managers and manufacturers as never before, while material
manufacturers have in recent years applied their new, noise-reducing materials to the off-road
machines market.
Next, the presenter discussed remaining challenges and opportunities. One challenge is
that power densities in off-road machines are continually increasing with no increase in the
machines' size. Increasing the dynamic power on a platform usually results in higher noise
levels. In addition, the cost of noise reduction is a constant hurdle for manufacturers. They have
also faced a changing customer base, as equipment is more often sold today to major fleets and
113
large operations; therefore it is not always clear to whom an improved operator environment is
being sold and whether it is worth the increased costs.
Washburn summarized the status of U.S. off-road machine manufacturers in designing
quieter machines: “If you look at the amount of laboratory equipment, hardware and software
tools, and people—highly trained people—that have gone into [noise reduction] in the last
decade, it's actually an enormous investment.”
Opportunities are increasing for noise control engineers to contribute their specialized
knowledge in the off-road machine context, Washburn said. As off-road machine manufacturers
are required to understand such issues as the EPA Tier 4 emission requirements and fuel
economy, they are looking at the machines from a systems perspective, requiring systems
engineering expertise. This approach is much more amenable to designing quiet machines.
Washburn concluded his presentation by speaking to the power of computation. He
illustrated the past decade's advances with a computation based on a project he conducted in
2013, using Lattice-Boltzmann Method Computational Fluid Dynamics (CFD) to estimate
cooling fan noise. The computation predicted the noise from a particular fan setup to within
about a dB straight from CFD—a feat he pointed out was impossible 10 years ago.
Figures 3.12-5, 3.12-6, and 3.12-7 illustrate his views of the future for off-road machine
engineering noise control challenges, new materials, and computational tools.
A history of “noisy machines”
Off-road machines are all about FUNCTION
• Perform the desired task(s)
• As efficiently and quickly as possible
• For the least cost (initial $, fuel consumption, maintenance)
• Everything else was secondary
• Safety (!)
The “old days”:
• Comfort
NOISE = POWER
• NOISE
Technology for a Quieter America, Keck Center, October 6-7, 2015
Figure 3.12-1 In the old days, noise = power.
114
4
A history of “noisy machines”
Bare (exposed)
operator station
Unmuffled or poorlymuffled exhaust
Open engine
compartment
Inefficient steel paddle
cooling fans
5
Figure 3.12-2. The noise environment of older machines.
Why so noisy? So many sources!
• Internal combustion engines
– Intake, Exhaust, Turbos
– Compression and combustion
Exhaust
– Mechanicals
•
•
•
•
•
Cab HVAC
Intake & Turbos
Hydraulic systems
Engine
Cooling fans
Powertrain
Cooling
Hydraulics
Drive trains
Cab HVAC
Functional Tools & Material Handling
Figure 3.12-3 Many noise sources.
115
Functional
Tools &
Material
Handling
6
Engineering
Figure 3.12-4. Examples
of modernQuieter
quieter machines.
Off-Road Machines
Karl Washburn, RSG & Eric Wood, Acentech
October 1, 2015
A view to the future: Challenges
• Plenty of machine forms still need work!
• Constantly increasing power densities lead to
higher noise levels
• Cost, weight, parts count, manufacturing,
support, …
• Who is “the customer”?
– Owners, fleet managers, operators
• Competition for trained talent
• Systems engineering
– Move beyond “slap some foam… here!”
Figure 3.12-5 Future challenges.
116
13
A view to the future: New materials
• Micro-perforated panels & poly fiber absorbers
– Formulated for harsh, off-road environments
• Multi-layered treatments
– (absorbing + blocking + damping)
14
Figure 3.12-6 Future materials.
A view to the future: Computational Tools
• Advanced acoustical &
vibration modeling
• More commercial
software with better preand post- tools
• Much more computer
horsepower & storage
• Cross-functional
analyses with mechanics
& fluid dynamics
Figure 3.12-7 Future computational tools.
117
15
3.13 MINING NOISE SOURCES AND THEIR CONTROL
James K. Thompson—JKT Enterprises
Day in and day out, miners are exposed to intense machine noise, which explains the pervasive
hearing loss within this group. While the federal government has developed technologies to tone
down the deafening sounds, the extra cost has so far been a barrier to widespread use.
Jim Thompson, of JKT Enterprises, spoke about noise in the context of the mining industry,
which he pointed out has a unique set of priorities and motivators in this regard. Focusing mostly
on underground mining, Thompson discussed noise overexposure; motivators for noise control;
progress; and remaining challenges.
Underground mining, in particular, is associated with major noise problems, thanks to a
contained environment in which people can work next to high-powered machines for 8 and even
12 hours each day. And, Thompson pointed out, the noise problem in mines has been
consistently increasing over the last 15 years, due to pressure for mines to become more
productive, which has translated into longer hours for workers and the use of bigger, more
powerful machines.
About 80 percent of underground miners (both metal/nonmetal and coal miners) suffer
from hearing impairment by age 60. Despite the condition's prevalence and seriousness, hearing
impairment is not a priority concern in mining operations, Thompson said. Figure 3.13-1 shows
data from CDC's National Institute for Occupational Safety and Health (NIOSH) about noise
overexposure and hearing loss among miners.
Many miners are overexposed to noise every day they go to work; the typical noise level
in underground coal mines and some metal/nonmetal mines is 95 to 100 dB(A). In “room and
pillar” coal mining, machines run continuously. In a so-called continuous mining machine, the
predominant noise source is the impact on other metal surfaces and the tail roller of the flight
bars on the conveyor chain that conveys coal to the rear of the machine to pick-up by the shuttle
car. This impact of metal on metal creates noise levels as high as 110 dB(A) around these
machines.
Despite the seriousness of the problem for miners, Thompson stated, no corporate and
marketing pressures have been brought to bear to decrease noise from these continuous mining
machines. Instead, it is the federal government that has led the way, with the cooperation of
manufacturers. NIOSH has developed some solutions, shown in Figure 3.13-2, such as a dual
sprocket chain that stabilizes the motion, and urethane-coated flight bars that reduce noise from
the impact. In some cases, these types of equipment adjustments have reduced sound power by 9
dB(A) (from 118 to 109 dB(A)), as illustrated in Figure 3.13-3. “So big changes are possible,”
Thompson summed up, “by making some pretty simple changes to the mechanism itself.”
For a mine, incorporating these types of improvements comes at a significant cost,
however. Manufacturers have priced the dual sprocket chain at about 50 percent higher than the
standard chain, and the dual sprocket chain with the urethane coating doubles the cost.
Thompson next spoke about longwall coal mining, illustrated in Figure 3.13-4, in which a
machine runs up and down the coal face stripping off coal. Roughly 50 percent of coal produced
from underground in the U.S. is mined with this “very big, efficient”—and noisy—machine
(with the other half done by room and pillar). The operator sits in a confined, reverberant space
118
next to a machine with a 500- to 1,000-horsepower (373- to 746-kW) motor running the cutter all
day long.
NIOSH, working with a manufacturer, was able to redesign the cutting head to reduce
noise. Changes to reshape the modal response of the machine's drum were developed
electronically and ultimately demonstrated in the field. The project achieved a significant 3
dB(A) improvement at high frequencies, with an extra cost of less than 10 percent because the
current drum was retrofitted. Information about this approach appears in Figure 3.13-5. The plan,
Thompson said, is to work on achieving even greater noise reductions.
The longwall system also uses a noisy stage loader, which includes a coal crusher,
conveying equipment, and hydraulics. Quieting this part would require enclosing it, Thompson
said, a prospect that has not received much attention to date.
The presenter discussed metal/nonmetal mining noise next, which involves different
sources and types of noise such as those associated with entering very small or very large spaces;
repeatedly drilling holes and blasting; and carrying mined ore by haul trucks. One area of focus
for noise reduction in this setting has been the cooling fan. As illustrated in Figure 3.13-6,
significant reductions, from 102 to 93 dB(A), have been achieved by switching to a larger fan
and running it at lower speeds with a better blade design. With this change, allowable exposure
time increased from 1.6 to 5.1 hours.
Thompson next listed additional sources of noise in metal/nonmetal mining: “jackleg
drills,” tools for horizontal drilling that expose operators to not only noise, but hand-arm
vibration (as well as the risk of injury from flying pieces of rock); and jumbo drills, which drill
deep holes for blasting and expose operators to noise levels that can reach 127 dB(A) or higher.
Some jumbo drills have cabs that were designed for dust control, but also benefit users by
controlling noise.
In summary, Thompson said effective noise controls exist in some areas, but not yet in
others. Even available controls are limited in their use. “We’ve gotten some people to use them,
but it's a very topsy-turvy environment in which the government is coming up with the noise
controls and then trying to get people to use them.” Mining equipment manufacturers are
receptive to learning about quieter equipment, but without noise control engineers on staff,
designing products with noise control measures has not been a priority. And designing quieter
systems is the best path to solving the noise problem, he said. “We've struggled trying to get
mining equipment manufacturers to see that, and to make the investment.” Given the decreasing
price of minerals, which makes operational costs a growing concern, winning attention to noise
issues “gets to be a bigger and bigger problem.”
Following his presentation, Thompson was asked about the availability of robotics in the
mining industry to reduce humans' exposure to noise. He responded that sophisticated
technologies have been developed, but that there has been resistance to automated approaches
that could cost miners their jobs.
119
Noise overexposure and hearing loss are
“facts of life” for miners
Percent with hearing impairment
100
UG Metal
Coal Prep. Plants
UG Coal
Surf. Coal
Stone (Surf. & UG)
Sand & Gravel
0
20
40
60
80
100
80
Metal/nonmetal miners
60
40
Coal miners
20
Non-noise exposed
0
20
25
30
Percent of exposures exceeding MSHA PEL
5/8/2016
35
40
45
50
55
60
65
Age
Source: Miners sampled in NIOSH Cross-Sectional Surveys
Source: John Franks, NIOSH
MINING NOISE SOURCES AND THEIR CONTROL– J K THOMPSON
5
Figure 3.13-1 Miners' noise exposure and hearing loss.
Continuous Mining Machine Solutions
• Dual sprocket chain standard product from Joy Global – fitted on
35% of operating CMMs
• Coated flight bars an option from Joy Global – number of units old
represents less than 5% of operating CMMs
• Dual sprocket chain 50% price increase
• Coated flight bars 100% price increase
• Best solution is a new design with noise
reduction as a key parameter
5/8/2016
Figure 3.13-2 Reducing noise from continuous mining machines.
120
11
Evaluation of Controls
Joy 14CM-9 with Standard Joy Chain
Standard Chain: 118 dBA
Urethane Coated Chain: 112 dBA
Urethane Coated Chain and Tail Roller: 109 dBA
110
100
90
80
70
al
l
ve
r
O
8,
00
0
10
,0
00
6,
30
0
5,
00
0
4,
00
0
3,
15
0
2,
50
0
2,
00
0
1,
60
0
1,
25
0
80
0
1,
00
0
63
0
50
0
40
0
31
5
25
0
20
0
16
0
12
5
60
10
0
A-weighted Sound Power Level (dB)
120
1/3 octave band center frequency (Hz)
5/8/2016
10
Figure 3.13-3 Controlling mining noise.
Longwall Mining System Shearer
o Roughly 50% of the coal is mined using the
longwall mining system
Cutting drum
Shearer
Shields
o Over 305 m long
o Operators follow the course of the shearer
along this length for each pass
o Confined and highly reverberant space
AFC
5/8/2016
Figure 3.13-4 The longwall mining system.
121
13
Shearer drum noise control
• Field trials confirmed lab and modeling
results – 3 dB(A) reduction achieved (96
– 93 dB(A))
• Further work to make more significant
noise reductions – extra cost less than
10%
• Noise from armored face conveyor
(when lightly loaded) may be a limiting
factor – may require additional controls
5/8/2016
15
Figure 3.13-5 Noise reduction in longwall mining.
Evaluation in Field
• Resulted in a 9 dB reduction in the TWA
• More than tripled the time to reach the MSHA PEL
• Maintained adequate airflow
5/8/2016
• Stock condition, or baseline
• New barrier material Duracote 5356
• 32” sickle fan and fan hub pulley ratio from 1:1 to 0.9:1
Figure 3.13-6 Cooling fan noise reduction in metal/nonmetal mining.
122
21
3.14 NATURAL GAS PIPELINES: NOISE FROM COMPRESSOR STATIONS
AND OTHER SOURCES
Reggie Keith - Hoover & Keith, Inc.
Natural gas pipelines, no matter the type, require compression stations with the potential to
create disturbing levels of noise in a community. But Federal Energy Regulatory Commission
regulations limit sound levels, leading facilities to enclose compressors and take other noisecontainment measures.
Reggie Keith, of Hoover & Keith, spoke about compressors and other sources of noise associated
with natural gas pipelines, and interstate pipelines in particular. This topic has been “very
dynamic” for the last 20 years, he said, as the environment on both supply and demand sides is
constantly evolving.
As background, Keith stated that the continental U.S. contains about 200,000 miles
(322,600 km) of interstate pipelines, which range in approximate diameter from 20 to 40 inches
(50 to 100 cm) (the biggest practicable size for seamless pipe). Natural gas travels through the
pipeline at pressures ranging from 200 to 1,500 psi, and every 40 to 100 miles (65 to 160 km) or
so is a natural gas compressor station. The lower the pressure, the more compressor stations are
needed. Distributions from the main pipelines to the end user require the pressure be reduced to
less than 300 psi for a large electrical power plant to less than 10 psi for residential use. In
addition to clean-source power generation, uses of natural gas include feedstock for
petrochemical and the manufacture of hydrogen for car fuel or another use.
The sound from compressor stations—such as the station shown in Figure 3.14-1, which
has run continuously for more than 50 years—can disturb neighbors. In the 1970s, as the pipeline
industry was developing delivery systems, it faced the challenge of handling environmental
sound in the face of only scattered local regulation. In response, the Federal Energy Regulatory
Commission (FERC) created noise regulations within the provisions of the Natural Gas Act of
1938 to govern the development of new natural gas compressor stations or augmentation of
existing ones. At the nearest existing noise-sensitive area—typically a residence, school, or
house of worship—sound was limited to a day-night sound level (“LDN”) of 55 dB(A). This
number came from the EPA's 1974 report “Information on Levels of Environmental Noise
Requisite to Protect Public Health and Welfare with an Adequate Margin of Safety.”
The day-night average sound level is not a direct measurement, but rather is computed
based on daytime and nighttime measurements. The associated formula appears in Figure 3.14-2.
The formula is a skewed average using nighttime sound levels (between 10:00pm and 7:00am)
that are 10 dB higher than the actual ones. Explaining this sound level metric to a pipeline
representative can be challenging, Keith pointed out. Given an LDN of 55, with daytime noise
levels equal to nighttime noise levels, compressor stations run at a constant “purr” without spikes
and dips; by this assumption, measuring 48.6 dB(A) translates into a 55 LDN level.
Having an objective permit condition of LDN 55—an absolute, not relative, criterion—
removes the challenge from persuading company representatives to reach the level, Keith stated.
The regulation specifies that 60 days are allowed from the time production is initiated to create a
report demonstrating compliance. If that fails, the facility is granted a year to make modifications
and submit a report showing compliance. Because of the prospect of having a $200 million to
123
$300 million project shut down, noise mitigation in design has become an essential part of the
development process.
Compressor stations tend to be classified according to two technological factors, the
driver and the compressor. Three major types are: reciprocal compressors driven by
reciprocating engines; centrifugal compressors driven by combustion turbines; and reciprocal or
centrifugal compressors run by electric motors. The devices themselves are no less noisy than
they were 30 years ago when he started working in this field, Keith said, “and they're not going
to get quieter.” And so the sound must be managed using add-on noise control treatments, he
said.
For example, a typical compressor unit out in the field emits engine and compressor noise
by its operation. To address fan noise—the biggest offender—and exhaust noise, the compressor
can be housed indoors, with the fan on the outside. Most cooling fans are inefficiently designed,
Keith explained, without consideration to aerodynamics. Reducing fan noise relies on reducing
fan speed, so the goal is to move the same amount of air with slower fan speeds.
Figure 3.14-3 shows a high-efficiency station for a reciprocating engine-driven unit.
Engines are housed inside a high transmission-loss (TL) building, and relatively large mufflers
are used, to reduce both low- and high-frequency sounds. The direct-drive coolers are no longer
used, eliminated in favor of motor-driven coolers. More, bigger, and lower-speed fans are used,
and variable frequency drives (VFD) can avoid the need for fans running at a constantly high
speed.
Figure 3.14-4 shows a combustion turbine-driven centrifugal compressor inside a
building that has internal sound absorption to reduce the sound within the building which also
reduces the sound that is transmitted through the building walls. Outside the high sound
transmission-loss building are high-performance exhaust and intake mufflers, along with
acoustical pipe lagging.
Figure 3.14-5 shows an electric motor-driven compressor inside a building. With the
4,000-horsepower (3000-kW) electric motor, of course electrical service is needed, but the
upside is the building need not have many openings.
Keith next discussed a meter station with a meter skid coming off the main line. Noise
can be created in several ways—by the required drop in pressure, for example, and by an orifice
needed for measurements.
The presenter concluded by speaking about a type of compressor station introduced in the
U.S. in the mid-1990s, when fuel supplies were low, to import and store foreign-source liquefied
natural gas. More than a decade later, when the gas supply returned to high levels, these stations
were transformed into liquefaction facilities to liquefy extra gas and sell it. This type of gas
processing facility, shown in Figure 3.14-6, amounts to a “giant refrigeration plant” that can
liquefy incoming gas, reducing its volume by about 600 times as it waits to be shipped out in
special tanks as needed. A single-train facility can require about 300 12- to 14-foot (3.7 to 4.3 m)
diameter fans—presenting a challenging noise issue.
124
Not So Fun Fact:
People do not like the sound of
Compressor and Meter Stations!
Figure 3.14-1 Noise from compressors and meter stations can irritate neighbors.
Federal Energy Regulatory Commission
(FERC)
Regulate many aspects of interstate pipeline
systems
Including approval, permitting and siting for
new projects and expansions of existing
facilities.
Currently the baseline noise environmental
noise criterion is an A-weighted Day-Night
Sound Level (Ldn) of 55 dB
9
æ 15
ö
Ldn = 10 log10 ç 10 Ld /10 + 10 ( Ln +10 )/10 ÷
24
è 24
ø
Figure 3.14-2 LDN level must meet FERC requirements.
125
Engine Driven Reciprocal Compressor Installation
Large Engine Exhaust
Mufflers
High TL Bldg.
Low Speed Electric Drive
Coolers
Figure 3.14-3 Higher-efficiency station for reciprocating engine-driven compressor.
Combustion Turbine Driven Centrifugal
Compressor Inside Building
Combustion Turbine Driven Centrifugal
Compressor Inside Building
Figure 3.14-4 Combustion turbine-driven centrifugal compressors.
126
Electric Motor Driven Reciprocating
Compressor
Electric Motor Driven Reciprocating
Compressor
Figure 3.14-5 Electric motor-driven reciprocating compressor.
LNG Liquefaction Facilities
Figure 3.14-6 Liquefaction facility.
127
3.15 NOISE CONTROL ENGINEERING FOR MILITARY NOISE SOURCES
Kurt Yankaskas - Office of Naval Research
The U.S. Navy's research investment in noise control and hearing conservation has achieved
engineering breakthroughs that promise to safeguard the health—and improve the professional
performance—of military service members.
Kurt Yankaskas, program officer with the Office of Naval Research's (ONR) Noise-Induced
Hearing Loss Program, spoke about the noise Sailors and Marines are commonly exposed to, and
about the Navy's progress and plans in the context of hearing conservation for improved health
and job performance.
The military is interested in hearing conservation because noise is pervasive throughout
the military system, in both operations and training. Some examples of noisy settings:




Carrier flight deck—126 to 150+ dB(A)
Aircraft cockpits—115 to 120 dB(A)
Amphibious vehicles—105 to 118 dB(A)
Engine rooms—84 to 118 dB(A)
Not only is noise a health hazard, but it also affects performance. “If you can't hear what's
going on, you can't hit the target,” Yankaskas said. In a 1991 U.S. Army study, Garinther and
Peters showed performance of tank gunners declined with poor speech intelligibility. In other
words, the harder it is to understand speech (commands) as found in high noise environments,
the harder it is to aim and hit the correct environment. Similar results are found in a series of
experiments being conducted by Dr. D. Keller at the Naval Surface Warfare Center-Dahlgren.
And beyond health and safety, the monetary costs of hearing issues are high and climbing along
with incidence: The cost to the Veterans Administration (VA) disability compensation system is
about $2 billion annually for hearing loss and tinnitus.
The Office of Naval Research established a Noise-Induced Hearing Loss (NIHL)
Program in 2008 that conducts the full spectrum of basic to applied research with a multidisciplinary approach. The NIHL portfolio includes four major research areas (lanes) that are
depicted in Figure 3.15-1. In the noise context, it is difficult to fully understand susceptibility
characteristics and incidence rates, Yankaskas stated: “It's noisy everywhere, but our Sailors and
Marines move around every couple of years so they get different exposures.”
The Navy has 40 dB earplugs, but these devices can act as a hindrance by blocking out
useful sound. For example, Soldiers and Marines in combat rely on hearing even very faint
sounds. To find a better way, Yankaskas said, the Navy is working to marry hearing aid, cochlear
implant, and microphone technologies.
Yankaskas called the Navy's diver helmet one of ONR's “huge successes.” Inhaling at
depth exposes a diver to 97 dB(A) each time, and over a couple of decades, divers experience
high levels of hearing loss. In a recently completed project, 27 dB of this exposure has been
removed by putting a simple muffler on the expansion chamber to control airflow. Some other
recent ONR successes in noise reduction are shown in Figure 3.15-2.
128
Of the critical nature of the Navy's noise engineering research in the combat context, the
presenter said: “Noise control is a warfighter performance enhancer. Our primary objective is to
win the battle, and noise is a distracter. It gives away your position.”
Over 30 or 40 years, the Navy's submarines have gotten significantly quieter, and the
Navy's destroyers got quieter by about 30 dB with a $60 million investment. Aircraft carriers,
once the “acoustic monolith” of the U.S. Navy, are now significantly quieter, thanks to a modern
quiet propeller developed by the Navy, which is the same sort of propeller in modern fans on
today’s cars.
Progress in noise reduction in ships was achieved, in part, by contract incentives for
quieter products. The use of higher-quality, resiliently mounted equipment such as balanced
pumps and balanced motors have paid off in terms of smoother performance and less
maintenance required.
In its gas turbine ships, a difference was observed between the CG47 and DDG51, with
the latter having a noise exposure dose about 5 dB lower. The engine room specification had
been changed for the DDG51 to 90 dB(A) by changing engine room components such as fans
and ventilation. All told, about 80 ship alterations were developed and used within the U.S. Navy
to reduce noise exposure. Figure 3.15-3 shows common sources of shipboard noise, and Figure
3.15-4 shows the results of some investments in quieter submarines, surface combatants, and
carriers.
Focusing next on warfighters in particular, Yankaskas played a video recording of an F18 launch, pointing out that people are within a wingspan of the intense noise—above 130 dB(A)
lasting 30 to 40 seconds. A person can adjust to the noise to some degree, but still, “It is noise
hazardous by definition,” he said.
Directly below in berthing spaces the noise levels are 89 to 105 dB(A). The overhead is a
primary path, with vibration measurements demonstrating high vibration levels. To reduce the
noise sufficiently, not only does the overhead have to be treated, but so do the bulkheads which
are additional radiating surfaces.
Under an ONR contract, a prediction and analysis tool called “Designer NOISE™” was
developed by Noise Control Engineering, LLC to support engineering solutions for reducing
noise and vibration on ships. Using a CAD-based model borrowing instrumentation from the
automotive industry, the Navy created a 3-D acoustic holograph, as shown in Figure 3.15-5.
With 32 microphones and a camera, the device takes a picture of the room, and acoustic intensity
is laid over it. The “red hotspot” revealed the structural bulkhead; treating this surface alone
dropped the noise level by 7 to 8 dB—a 75 percent weight savings over blindly treating all five
surfaces.
Figure 3.15-6 summarizes the Navy's process for mitigating noise on the gallery deck, a
process currently being applied to the USS Dwight D. Eisenhower. To verify the extensive
model, the Navy covered about 21 percent of the area under the flight deck with 112 sensors to
map the acoustic propagation throughout the structure and its piping and also airborne paths. The
model is then imported into the computer with drawings.
Figure 3.15-7 shows predictions for gallery deck noise before and after treatment.
Reducing noise by some 20 dB(A) would require the treatment of the whole gallery deck, adding
100 tons (91 tonne) of weight to a ship. Given the added weight penalty of this approach, the
Navy is continuing to evaluate which critical areas to treat.
The Navy is also modeling hydroelectric plants using this technology for the Bureau of
Reclamation. After measuring and modeling some dams and applying noise control to some
129
smaller hydroelectric plants, noise levels have been decreased by 7 to 10 dB. To achieve this,
ceramic damping was sprayed on. The easy-to-spray material also acts as a vapor barrier,
Yankaskas said, which can address problems associated with chill water piping eventually
dripping onto the deck. Reduction of condensation dripping on the deck can help combat ship
deck rusting that requires deck replacement.
The same design modeling tool “Designer NOISE™” technology that has already been
applied to ships and vehicles is being applied to structures and will ultimately be applied to
aviation hangars, Yankaskas said.
Noise-Induced Hearing Loss Portfolio
Systems Approach for an Integrated 6.1 / 6.2 / 6.3 Program
Source Noise
Reduction
Medical Prevention &
Treatment
Incidence, Susceptibility
& Evaluation
Cell regeneration
Assessment tools
Personal Protective
Equipment (PPE)
Shipboard PPE
Shipboard noise
assessment
Pharmacologic interventions
and drug delivery
Shipboard noise
path validation
3D Digitization for
“Prescription” Ear Plugs
Hearing loss simulator
Jet noise
Reduction
In-Ear Dosimetry
Laboratory
modeling/ scale tests
of jet noise reduction
Modeling Tools
Blast interventions
Underwater comms &
hearing protection
3
Figure 3.15-1 ONR's NIHL research portfolio for noise-induced hearing loss.
130
Source Noise Reduction
Goal: To reduce hazardous noise exposures at the source
FY08 – 14 Achievements:
• Successful First 3-D Acoustic Holography Measurement 2012
• Enabled Verification of CVN acoustic model (Designer Noise),
2012
• Developed Acoustic Damping Treatments to Mitigate Hazardous
Noise on an aircraft carrier 2012/13. Planned installation on
CVN 72
• JSF DT-1 testing Nov 2014
• Developed Diver Helmet breathing noise reduction 2014
• Measured USMC transport vehicle, 2012,
• MIL-STD 1474E Noise Requirements for shipboard noise control
• Developed Jet Noise Reduction via modeling and simulation
• Full Scale chevrons tested on F/A-18E tests w/ GE, 2012
• F-35 Jet Noise Reduction Concepts Study completed 2013
• Published ANSI ASA S12.75-2012, Methods for the
Measurement of Noise Emissions from High Performance
Military Jet Aircraft September 2012
Shipboard noise
assessment
Shipboard noise
path validation
Jet noise
Reduction
Laboratory
modeling/ scale tests
of jet noise reduction
UNCLAS, Distribution Statement A: Approved for public release; distribution is
unlimited.
Source Noise Control – Warfighter Performance Enabler
4
Figure 3.15-2 Examples of ONR's recent accomplishments in noise reduction.
Shipboard Noise Control
Sources of Noise are well known !
The
usual
acoustic
culprits:
–Fans
–Ventilation
–Motors
–Pumps
–Propellers
6
Figure 3.15-3 Major sources of shipboard noise.
131
Previous Quieting Investments
CV 63
CVN 68
CVN 76
CVN 78
Noise Level
FF 1040
FF 1052
LCS
DD 963
CG 47
DDG 51
DDG 1000
SSN 594
SSN 637
SSN 688
SSN 688I
Surface Combatants (S0229) & Submarines
Have a Legacy of Acoustic Quieting
(Time & Money Investments)
SSN 21
NSSN
Time
5
Figure 3.15-4 Investments in shipboard noise reduction.
Acoustic Holography Array
SR-03-92-0-L Cat 2 Launch - Hornet
Structural Bulkhead
Looking FWD
Non-Structural Bulkhead
Looking Aft
Overall SPL in SR-03-92-0-L: 91 dB(A)
13
Figure 3.15-5 Acoustic holograph technology.
132
5
Engineering Controls to Mitigate Noise
on Gallery Deck
Technical Approach:
• Predict noise levels using Designer NoiseTM software
• Test program undertaken on USS Dwight D. Eisenhower (CVN69)
–
–
–
–
•
Use test data to:
–
–
–
–
•
Area of focus: “12-pack” area under Catapult #2
Baseline measurements taken prior to application of controls
Apply spray-on damping material on bulkheads
Retake measurements to determine effectiveness
Validate noise model accuracy (treated and untreated)
Validate source level assumptions
Verify effectiveness of treatment
Quantify acoustic and structureborne energy paths into gallery deck
Use validated noise models to develop optimized noise control
treatment plan for full gallery deck
14
Figure 3.15-6 Gallery deck noise mitigation.
Predicted Noise Level Maps
(CVN Gallery Deck)
Before Treatment
After Treatment
17
Figure 3.15-7 Gallery deck noise predictions, before versus after mitigation.
133
3.16 NATIONAL AND INTERNATIONAL NOISE EMISSION STANDARDS
FOR CONSUMER AND INDUSTRIAL PRODUCTS
Robert Hellweg - Hellweg Acoustics
Noise emission standards, including ISO and ANSI standards, have served as an instrument in
product noise measurement and control, while stimulating the development of quieter consumer
products and industrial equipment. Standards are continually created and revised as needed to
improve measurements and spur additional progress in noise reduction.
Robert Hellweg—an expert in noise emission standards who has worked as a noise control
engineer for the Illinois Environmental Protection Agency, the computer industry, trade
associations, and most recently an environmental firm—spoke about noise emission standards
and their effect on consumer and industrial products over the last 10 to 20 years. Specifically, the
speaker addressed topics including national and international standards themselves, some
product-specific standards, the impact of standards on product development, and the role of
standards in quieting products.
Noise emission standards can be used as a tool in product noise control, and may have
contributed to the significant progress seen over the years, Mr. Hellweg stated. For coverage of
the ISO and IEC standards in general, the speaker suggested three papers, listed in Figure 3.16-1.
Standards support product development in many ways. For example, they improve
competitive analysis. Manufacturers have an accurate knowledge of the noise emissions of their
competitors’ products; measured product noise values are accurate; and measurement techniques
are reliable, repeatable, and practical and reflect actual operating and mounting conditions.
Changes measured in a product after noise mitigation reflect reality, not measurement
uncertainties. Data from measurements can be used to predict product noise emissions from
component measurements during the design stage, before prototypes become available; to help in
specifying components such as fans, compressors or motors; and to support accurate noise level
reporting to customers and regulatory agencies. (See Figure 3.16-2.)
Mr. Hellweg briefly summarized the basic sound power standards. The ISO 3740 series
includes seven different standards, summarized in Figure 3.16-3, which have all been modified
within the last five years. Additional standards include a new standard on high-frequency sound
power levels, as well as sound intensity standards. The presenter noted that these sound power
standards are available as ANSI national adoptions, and can be obtained via the Acoustical
Society of America (ASA) website (at a significant discount for ASA members).
The speaker mentioned that major recent changes to these standards include the addition
of information on uncertainty in noise measurements. ISO 3744 has seen two major changes:
The environmental correction factor K2A for a measurement laboratory has increased from 2
dB(A) to 4 dB(A) but there are no octave band requirements for the environmental correction.
However, the uncertainty did not change in the standard. Also, the default hemispherical
measurement surface was changed to the one applicable to a product with tones. Manufacturers
with many products, Mr. Hellweg pointed out, often build a test chamber to meet the more
stringent ISO 3745 chamber requirements to eliminate consideration of the environmental
correction.
Mr. Hellweg returned to discussing the measurement of high-frequency sounds (in the 16
kilohertz octave band) in ISO 9295, which considers larger air absorption and the high directivity
134
of these sounds. Where previously the standard applied only to information technology (IT)
products, it is now applicable to all types of products.
The presenter next discussed emission sound pressure level standards, which are sound
pressure levels at an operator's position—measured in a hemi-anechoic environment and not
taking into account workspace factors such as reflections from walls. There are five basic ISO
standards in the ISO 11200 series that apply in this regard.
Noise declaration standard ISO 4871 covers the reporting and declaration of a product's
sound emissions. Two quantities are important: the mean value, which is measured, and the K
factor, an overall uncertainty taking into account unit-to-unit variations and measurement
uncertainty. And there are two ways of reporting sound emissions under the standard: a
combined single number representing an approximate maximum statistical value; or reporting
both the mean value and K factor. A draft U.S. standard by the ANSI/ASA S12 standards
committee is preparing an American version of the very old ISO 4871.
Product-specific noise emission standards specify the aforementioned applicable ISO
standards for measuring sound power and sound pressure and include operating and mounting
conditions for particular product types, such as printers, saws, refrigerators, etc.
New standard ISO 26101, approved in 2012, applies to anechoic and hemi-anechoic
chambers. Along with the latest revision of ISO 3745 on hemi-anechoic rooms, the new standard
eliminated a loophole relating to chambers and the determination of the 6 dB drop-off with
distance. The new ISO 26101 inadvertently caused some good chambers to fail this requirement;
however, amendments to ISO 3745 and ISO 26101 are being written to correct this issue.
Standards exist for two metrics relating to sound quality: loudness (ISO 532 and
ANSI/ASA S3.4) and prominent discrete tones (ISO/PAS 20065, ISO 7779 Annex D and
ANSI/ASA S1.13 Annex A). The 40-year-old ISO 532 standard is the subject of two revisions:
one is an updated Zwicker method based on German standards, and the second is the MooreGlasburg for stationary (i.e., not time varying) sounds, based on a current American standard:
ANSI/ASA S3.4.
Next, the presenter addressed the fact that the acoustic standards' instrumentation sections
refer to IEC microphone and IEC sound level meter standards, but do not take into account
computerized data acquisition systems. The newly approved standard ISO 6926 on reference
sound sources added provisions for computerized data acquisition systems indicating they must
meet applicable sections of the new IEC sound level meter standard for periodic tests (IEC
61672:2013 Part 3).
Next, the presenter turned to examples of how standards have spurred product
development. To address the lack of meaningful sound power level data at the operating point of
fans, for example, George Maling developed a plastic plenum in which the fan is mounted. This
device, known as the "Maling box" and shown in Figure 3.16-4, could be adjusted to allow the
measurement of sound power levels under loading conditions approximating system conditions.
This plenum led to the development of a recommended practice in 1985 by an INCE/USA
technical group that, in turn, became an ANSI standard and then an ISO standard. This standard
has been used by the IT and other industries to assist in selecting fans for products.
An INCE/USA technical group also developed another recommended practice in 1996
for measuring structure-borne fan noise to address the problem of fans' vibration into computer
chassis. The recommended practice became an ECMA, ANSI, and ISO standard.
Figure 3.16.5 shows a half-size fan plenum in which a small fan is mounted to a damped panel
and vibration acceleration measurements are made near the fan mounting points.
135
With such standardized testing methods for fan sound power levels, it was possible to
have reliable fan specifications for product design. Fan manufacturers began providing
information on sound power levels based on these tests.
Another standard was born of a problem with computer equipment emitting highfrequency tones in the 16 kilohertz octave band. ECMA 108 was developed to measure the sound
power level of these products by addressing unique measurement problems associated with high
directivity and atmospheric absorption. It was an engineering grade standard with three
reverberation room procedures and one hemi-anechoic room procedure. ECMA-108 formed the
basis for ISO 9295, which is now applicable to all types of products and equipment.
Mr. Hellweg opined on the future developments of the ISO and ANSI sound power and
sound pressure standards. One goal is to simplify them. Consideration will be given to
consolidating lengthy measurement uncertainty sections in each of these standards into a single
standard. Also, the lengthy background noise correction standards may be shortened, with
atypical situations covered separately. An electronic guide is being developed to simplify the
application of ISO 3744. Since the standards are intended to cover 99 percent of situations
encountered, consideration will be given to cover some more complex issues in an annex,
thereby simplifying the basic standards.
An advisory committee for the ISO Technical Committee (TC) 43 (acoustics standards
committee) is preparing a guideline for instrument sections on computerized data acquisition
systems. (The content of the newly revised ISO 6926 mentioned previously is only a first step.)
ISO TC 43 will ask IEC—in collaboration with those using acoustic standards—to develop a
standard for acoustic data acquisition systems for use in ISO TC 43 standards.
Mr. Hellweg concluded his presentation by acknowledging the significant contributions
to acoustic and noise standards development by trade associations and other organizations,
including but not limited to AHRI, AHAM, AMCA, ITI, ASHRAE, ASA, ASME, ASTM,
ECMA, and INCE/USA.
136
Figure 3.16-1 More information about noise emission standards.
Figure 3.16-2 The role of acoustic standards in product development.
137
Sound Power Level Standards
• Reverberation Room
•
•
•
•
ISO 3741 (Precision)
ISO 3743-1 (Engineering)
ISO 3743-2 (Engineering)
ISO 3747 (Engineering or Survey)
• Anechoic
• ISO 3745 (Precision)
• Hemi-Anechoic Room
• ISO 3744 (Engineering)
• ISO 3745 (Precision)
• ISO 3746 (Survey
(All are available as ANSI National adoptions: ANSI/ASA S12.5x)
6
Figure 3.16-3 ISO 3740 series sound power level standards.
Figure 3.16-4 The plastic plenum, or "Maling box," for fan noise testing.
138
Figure 3.16-5 Half-size plenum with damped panel for measuring small fan airborne sound and
structure-borne noise (vibration).
139
140
4
INSTITUTES OF NOISE CONTROL ENGINEERING
4.1 INTERNATIONAL INSTITUTE OF NOISE CONTROL ENGINEERING
Rajendra Singh - The Ohio State University and I-INCE Vice President of Technical Activities
The International Institute of Noise Control Engineering (I-INCE) was founded in 1974. It is a
worldwide consortium of over 40 organizations concerned with noise control, acoustics, and
vibration. The primary focus of the Institute http://i-ince.org/index.php is on unwanted sounds
and vibrations producing such sounds when transduced. I-INCE is the sponsor of the INTERNOISE series of International Congresses on Noise Control Engineering held annually in leading
cities of the world. For instance, the next two congresses will be held in Hamburg, Germany
(INTER-NOISE 2016 http://www.internoise2016.org/) and Hong Kong (INTER-NOISE 2017
http://www.internoise2017.org/). I-INCE also co-sponsors symposia on specialized topics within
the I-INCE field of interest. The quarterly magazine Noise/News International (NNI) is jointly
published by I-INCE and the Institute of Noise Control Engineering of the USA (INCE/USA).
An overview of technical activities is given below and some elements are explained later.
Also, Noise/News International published an editorial by the I-INCE Vice President of Technical
Activities (Rajendra Singh) entitled “Expanding Horizons of I-INCE Technical Activities” in its
2012 June issue; the article is on page 47. Please go to http://i-ince.org/activities.php for more
details.
Activity
Summary
Overview of Technical Study
Groups (TSG)
Each group studies one important aspect of noise
and its effect on society, and then issues a formal IINCE report
Future Congress Technical
Planners Meeting (FCTP)
Plan the technical programs of next congresses and
offer advice on other aspects via meetings held at
congress
Young Professionals Grant
Program
Offers 12 to 18 travel grants (600 Euro per recipient)
to young professionals to attend the next INTERNOISE Congress
Young Professionals
Workshop
A mentorship session for young professionals and
students held at INTER-NOISE Congress
I-INCE Annually Sponsored
Symposia
Symposia on Noise sponsored by I-INCE
1.
Miscellaneous
I-INCE report on noise control engineering
education (based on the books on prior
education workshops).
2. I-INCE Website and Information
Dissemination
141
I-INCE instituted a program to undertake technical initiatives on critically important
issues of international concern within the I-INCE field of interest. This initiative has resulted in
several reports and a number of Technical Study Groups. Each group studies one important
aspect of noise and its effect on society, and then issues a formal I-INCE report. Recent reports
include the following: Lawrence S. Finegold, Guidelines for Community Noise Impact
Assessment and Mitigation, I-INCE publication no. 11-1, 2011; Philip J. Dickinson, Outdoor
Recreational Noise, Volume 1: A Review of Noise in National Parks and Motor Sport Activities,
I-INCE publication no. 12-1, 2012; Andre Fiebig and Paul Schomer, Supplemental Metrics for
Day/Night Average Sound Level and Day/Evening/Night Average Sound Level, I-INCE
publication no. 2015-1, 2015. Links to the above reports and more can be found at: http://iince.org/activities.php.
The Future Congress Technical Planners (FCTP) offer advice on technical program
aspects of a congress including the maximum number of parallel sessions, the type of structured
sessions, and plans for plenary or keynote and poster sessions. The FCTP may recommend new
concepts for future INTER-NOISE Congresses. The concepts may involve items that are specific
to a particular congress and which depend upon local circumstances and local ideas. The FCTP
holds two meetings at the INTER-NOISE Congress, a Pre-FCTP meeting on Sunday and the full
FCTP meeting on Wednesday. The Pre-FCTP meeting is an informal meeting wherein the
minutes of the previous FCTP meeting are discussed. The full FCTP meeting discusses the
technical plan for the next two congresses and the experience of the congress that has just ended.
In 2010, I-INCE initiated a grant program for noise control engineering students and
young professionals who are within the first 10 years of their careers. The goals of the grant are
to expose students and young acousticians to senior professionals, give them experience in public
presentation and paper writing, and assist them in developing networking abilities. In the
beginning, I-INCE allocated 12 to 18 grants, with 500 Euros per recipient, to pay for conference
registration and some travel expenses. This grant enabled these young professionals and students
to attend the INTER-NOISE Congress and network with senior engineers. The Board approved
an increase in the grant from 500 EUR to 600 EUR from 2014 (and at least 15 grants per year).
Over a seven-year period since 2010, I-INCE has awarded 104 I-INCE grants; successful
candidates have come from 34 countries of origin (and 30 countries of work). I-INCE has
allocated 10,000 EUR each (9000 EUR for at least 15 grants and 1000 EUR for the Young
Professionals Workshop) for INTER-NOISE 2016 and INTER-NOISE 2017. This would bring
the total allocation of funds by I-INCE to 72,500 EUR over eight years. Noise/News
International published a feature article by the Vice President of Technical Activities (Rajendra
Singh) entitled “I-INCE Young Professionals Program Offers Grants, Advice and Opportunity”
in its 2012 September issue. For more details, go to http://i-ince.org/travel_grants.php.
To meet the expanding needs of the noise control engineering field, I-INCE has also
established a Symposium series. Finally, I-INCE is assuming a leadership role in formulating
global noise policies; this includes an ongoing collaboration with CAETS (International Council
of Academies of Engineering and Technological Sciences). For further details, go to http://iince.org/.
142
4.2 INSTITUTE OF NOISE CONTROL ENGINEERING OF THE UNITED STATES OF
AMERICA
Eric W. Wood - Acentech Incorporated and INCE/USA Past President
The Institute of Noise Control Engineering of the United States of America (INCE/USA) is the
premier professional society dedicated to noise control engineering. We have about 800
members and associates from the U.S. and about 20 other countries. Members are from
universities, industry, government, consulting practices, and interested members of the public.
New members and associates are always welcome. Applications are available on our website at
www.inceusa.org. See Figure 4.2-1
INCE/USA has sponsored well-attended noise control conferences in North America
every year for 42 years—most recently, in San Francisco, Fort Lauderdale, and Denver.
We have 17 technical committees formed by people interested in particular aspects of
noise control engineering. As examples, we have one technical committee on sources and
propagation, another on passive noise control, another on transportation noise control, and
another on community noise. We have two new committees that address wind turbine sound and
motor vehicle noise.
Our members and associates receive two INCE/USA publications: the peer-reviewed
Noise Control Engineering Journal and Noise/News International, a quarterly publication
containing news on global noise control activities and noise generally. Members also have free
access to our INCE/USA digital library of more than 20,000 papers and journal articles on noise
control engineering that are searchable by key words, title, and authors. And our website offers
several public information documents for download without charge.
We have awards, honors, and travel grants for students each year funded by the INCE
Foundation. Additional awards include the Outstanding Educator Award, the Distinguished
Noise Control Engineer Award, the Award for Excellence in Noise Control Engineering, the
Distinguished Service Medal Award, the Martin Hirschorn IAC Prize for the best paper written
about noise control engineering during the past two years, the Leo Beranek Student Medals, and
the Laymon N. Miller Award for Excellence in Acoustical Consulting.
INCE/USA offers board certification to our exceptionally qualified members based on
education, experience, and passing an eight-hour professional exam. This is intended to be
similar to state-level professional engineering registration.
Questions about INCE/USA
contact me at
Membership in INCE/USA
We invite and welcome new members.
Eric W. Wood
INCE/USA, Past President
INCE Foundation, President
Acentech, Principal Consultant
Additional information is available at our website:
www.inceusa.org
A membership application form is also available.
Free membership for students, the future of our profession.
[email protected]
617.499.8034
www.inceusa.org
Figure 4.2-1 INCE/USA Membership Welcome and Q&A.
143
144
5
OBSERVATIONS
Workshop presenters addressed a wide variety of noise-associated issues in the context of
consumer and industrial products. A generation ago, machine noise was equated with power.
Loud construction machines with minimal exhaust mufflers were assumed to have the power
needed to get the job done. However, machine operators and workers in industrial plants suffered
noise-induced hearing loss. Household vacuum cleaners, dishwashers, kitchen fans, and clothes
washers could be heard throughout the home. Times have changed. Today, consumers still desire
power, but with less noise. And manufacturers have been responding with many quieter
products. It is now common to see advertisements that promote “quiet” and even “ultra quiet”
alongside “quality” and “efficiency.” This move toward less noise is also occurring within and
outside large industrial facilities.
Product manufacturers have determined that “quiet” pays as does “sound quality.” Lower
sound levels and enhanced sound quality both help to differentiate their products. They provide
additional brand recognition. They also increase sales and help the bottom line. And it has been
found that in the course of designing a product to decrease noise, sometimes performance is also
bolstered.
Product noise labeling methods and new standards are being developed to help inform
consumers wanting to use sound levels as a reliable part of their buying decisions. These new
labeling methods are similar to the fuel efficiency and energy efficiency ratings that have
become popular.
Listening panels that represent a cross-section of consumers are being used by engineers
to guide product design goals and directions.
Home appliances including waste food disposers, dishwashers, clothes washers, vacuum
cleaners, electric toothbrushes, and ventilation fans are now available that are considerably
quieter than they were a few decades ago. Even home-kitchen and commercial blenders are now
available that are considerably quieter than earlier models.
Leaf blowers used for lawn care are a significant source of annoyance for neighboring
residents, but a manufacturer has invested the time and effort to develop a line of leaf blowers
that can get the job done while producing about 10 dB(A) less noise than others.
Power and distribution transformers are now available that are as much as 20 dB quieter
than were typically available a few decades ago. This has helped during transformer site
selection studies and reduces the annoyance of local residential neighbors about tonal noise
radiated at even harmonics of the line frequency.
Automobile interior noise performance is being considered by manufacturers during the
design phase along with other performance elements such as visual appeal, fuel economy, power,
durability, safety, handling, and comfort. Interior noise for many small, medium, and large cars
has declined considerably during recent decades due to the focused efforts of noise control
engineers working with the manufacturers.
Reduced noise cabs are now available for large engine-powered mobile equipment like
that used in earth moving, mining, quarrying, construction, demolition, road building,
agriculture, forestry, and grounds care. Noise levels operators are exposed to are now much
145
lower than they were in the past, and are providing a safer and more comfortable work
environment for the operator. In a particularly quiet cab, the noise level is now as low as 70
dB(A). And industrial facility managers have learned that workers are more productive in a
workplace with lower noise levels.
Valves and piping operating in severe conditions, high gas flow rates, and high pressure
drops have been major noise sources within many industrial plants. But today plant owners
expect lower noise levels for various reasons, including protecting the safety and health of the
plant's employees; avoiding unnecessary disturbance of residential neighbors; and preventing
vibration-induced failures in the valves and piping systems. It is now recognized that “lower
noise is a good investment, not just an expense,” according to Acentech’s Eric Wood,
INCE/USA past president.Well-designed valves and piping systems are now available that
produce noise levels much as 10 to 40 dB(A) lower than earlier designs.
Large air moving devices have historically been a major source of noise, and highpressure high-flow centrifugal and axial fans were not quiet. Noise control engineers relying on a
combination of experimental techniques and continually improving computational capabilities
have developed fans that are more efficient while producing less noise.
Underground mining is noisy with people working for 8 and even 12 hours each day in a
contained environment next to high-powered machines. Many miners suffer from occupational
noise-induced hearing loss. Unfortunately, the noise problem in mines has been consistently
increasing over the past decade or two, due to pressure for mines to become more productive,
which has translated into longer hours for workers and the use of bigger, more powerful
machines. Effective noise controls exist in some areas in this context, but not yet in others.
Design modifications for continuous mining machines have been developed and tested that
reduce radiated noise by as much as 9 dB(A). The cooling fan for haul trucks carrying mined ore
has also been reduced by 9 dB(A). For longwall coal mining, updated designs of the cutting head
and the machine's drum were developed and demonstrated in the field that reduced noise by 3
dB(A) at high frequencies.
New standards are being published defining appropriate and consistent methods to
measure and report product and equipment sound pressure and sound power levels. Additional
standards are currently being developed. Some large stores are now showing noise ratings for
various products on their shelves that help consumers make informed choices. The INCE/USA
product noise committee is developing an enhanced product noise rating (PNR) method and logo
designed for widespread use.
The U.S. military’s considerable efforts and research investments in noise control and
hearing conservation are achieving engineering breakthroughs to both protect our Sailors and
Marines from excessive noise exposures and enhance their professional performance. Examples
include reducing shipboard noise, reducing diver helmet breathing noise, enhancing hearing
protection devices, reducing noise and vibration inside and outside of tracked military vehicles,
and reducing noise inside and outside of military aircraft.
Employees at power generation plants and nearby residential neighbors are benefiting
from the efforts of noise control engineers who are now incorporating equipment designed with
reduced noise including fans, transformers, and gears, as well as better mufflers and equipment
enclosures.
The Federal Energy Regulatory Commission (FERC) has adopted a regulation that limits
environmental noise from gas compressor stations to a day-night average sound level (“LDN”)
of 55 dB(A) at the nearest existing noise-sensitive area—typically a residence, school, or house
146
of worship. Gas transmission companies are now employing engineers and consultants to design
quieter gas compressor station.
Gears with a primary function of transmitting power are used in applications ranging
from the transportation arena (automobiles, off-road vehicles, helicopters, and submarines, for
example) to industrial equipment (including construction machinery, power plants, wind
turbines, and automation actuators) to consumer products (such as tools, hair clippers, toys, and
even baby swings). Engineers are learning about the generation and control of gear noise at
institutions such as The Ohio State University where a short course has been attended by more
than 1,900 engineers (from more than 350 companies) over 36 years. The 50 or so students (from
industry) in each class have been eager to learn about various aspects of gear noise.
Customers want lower-noise compressors for health and safety reasons, and better
standards have been developed to more accurately report product noise levels. With new
standards and a heightened interest in reducing noise, noise levels have decreased industry-wide
by 3 to 5 dB(A) and sometimes more.
Good progress has been made, but more needs to be done. With noise-induced hearing
loss costing the VA about $2 billion annually, there is clearly room for improvement.
Buy quiet programs need to be better known and more used. Manufacturers and buyers
need to know that more can be done to reduce noise emission levels.
The Nation needs academic research, and this research needs to be applied to innovative
product designs.
Existing technology needs to be transferred more widely. Government advances need to
be transferred to private industry and vice versa.
Even if competitive issues restrain the transfer of technology, examples of low-noise
technology need to be published and widely disseminated. If competitors know about others’
achievements in this area, they will have the incentive to do as well or better.
As for the cost per dB of noise reduction requested by a buyer of a new large power
transformer: When a buyer requests only a modest degree of noise reduction, the cost per dB is
relatively small compared to the total cost of the transformer. The cost per dB increases
significantly when the buyer requests a transformer with a large degree of noise reduction. The
additional cost for a quieted transformer is typically less than the cost of installing noise walls
surrounding the transformer instead.
The added costs for including appropriate noise controls at a new industrial project near a
residential area, or inside a new residential building, are typically less than the future costs of bad
will and litigation resulting from excessive uncontrolled noise.
Product sound quality engineering, the “sound of quality,” was a subject addressed during
many of the workshop presentations and the subject of several previous symposia conducted by
INCE/USA. It was said that quality sounds of a consumer product are not just a feature; they are
a benefit to both the manufacturer and the consumer. Manufacturers need to learn how to
communicate this to the public, as the presentation on kitchen sink food waste disposers
demonstrated.
Standards were identified as important to the noise control engineering profession. The
“product noise rating” (PNR) addressed during the workshop does not use decibels and is
expected to be useful to the public.
It was noted that post-occupancy evaluations by the Center for the Built Environment at
the University of California at Berkeley indicate noise and speech privacy are among the top
147
problems in buildings. Concern was expressed that those problems could get worse in greener
buildings, but ASHRAE and others are making progress in addressing such issues.
Today, unlike 20 or 30 years ago, noise control engineers’ use of advanced computational
fluid dynamics on modern computers is making quieter fans available for many air moving
applications.
Noise control engineers are dealing with increasingly complex “system problems” that
now often include multi-sources, multi-paths, and in many respects multi-receivers—thus raising
increasingly complex problems.
One challenge identified is understanding current and future customer noise requirements
and getting the requirements into product design cycles at an early stage. It was reported during
the workshop that an apparent linkage exists between hearing loss and early onset of dementia,
and that maybe common knowledge of this connection could help achieve change.
One presenter who receives products from other companies for laboratory testing has
observed a downward trend in noise levels because manufacturers want to gain that market
advantage. They want to be seen as the market leader, with the best—and quietest--product. That
applies to consumer home appliances and medical equipment. In the consumer world, quiet
equals quality, and that is expected to spread to other industries as they recognize the payback
from investments in noise control.
It was asked if salespeople bring up low noise as a sales advantage. One sales example
offered was the new geared turbo fan jet engine that produces less noise and provides increased
fuel efficiency. Another example offered was certain air conditioning equipment where reduced
noise and improved efficiency were two major design goals. One presenter mentioned that,
during a recent shopping experience at a large box store, salespeople brought up the noise
produced by several home appliances.
In association with a redesign of a home appliance to make it quieter, one presenter
reported that engineers invested a great deal of time educating the company’s own marketing and
sales forces on how to communicate with people—including not only end users, but also big box
and supply house executives--about the sound improvement. Sales kits included appliance parts
used to demonstrate the improvement. The extensive investment in internal education, and in
turn external education, was in recognition of an unavoidable fact: If you raise the product’s
price, you have to educate consumers about what they’re paying for.
148
Appendix A
Workshop Agenda
Progress on Consumer and Industrial Product
Noise Reduction
A Follow-up Workshop to the NAE Technology for a Quieter America Report (2010)
Organized by the INCE Foundation
An International INCE Symposium
6-7 October 2015
The National Academies Keck Center
500 5th Street, NW
Washington, DC 20001
Final Program
8:30 – 9:00
Welcome
Dan Mote, President, National Academy of Engineering
Opening Remarks
Adnan Akay, Eric Wood, and George Maling
Workshop Co-Chairs
Participant Introductions
Consumer Products at Home
9:00 – 9:20
Progress in Noise Reduction for Home Appliances
Wayne Morris, American Home Appliance Manufacturers
A-1
9:20 - 9:40
Evaluation of Consumer Product Noise
Mark Connelly, Consumer Reports
9:40 – 10:00
Sound Quality and Engineering Noise Control of Various
Consumer Products
David Bowen, Acentech Incorporated
10:00 – 10:20
Trends in Appliance Noise Control
Kevin Herreman, Owens Corning
10:20 – 10:40
BREAK
10:40 – 11:00
Kitchen Sink Food Waste Disposers
Cynthia Jara-Almonte
InSinkErator, Emerson Commercial & Residential Solutions
11:00 – 11:20
Yard Care, Quieter Leaf Blowers
Larry Will, Echo, Inc. (retired)
11:20 – 11:40
Information Technology Equipment
Marco Beltman, Intel
11:40 – 12:00
PNR. A Simplified Product Noise Rating Method for the
General Public
Matt Nobile, Hudson Valley Acoustics
12:00 – 1:00
Lunch in the NAE Cafeteria
1:00 – 1:20
Automobile Interior Noise
Shung H. (Sue) Sung, General Motors (retired)
1:20 – 1:40
Group Discussion: The Costs, Benefits, and Economics of
Noise Control for Consumer Products
Discussion Leader: Adnan Akay, Workshop Co-Chair
Commercial and Industrial Products
1:40 – 2:00
The Need for Quieter Machines for Industrial Facilities
Bob Putnam
2:00 – 2:20
Air-conditioning, Heating, and Refrigeration Institute
Standards’ Contributions to the Engineering of Quieter Products
Steve Lind, AHRI and Ingersoll Rand
2.20 – 2:40
BREAK
A-2
2:40 – 3: 00
The Contributions of ASHRAE TC2.6 in the Engineering
of Quieter Products and Progress in Noise Reduction for
Heating, Ventilating, Air-conditioning, and Refrigeration
Systems
Erik T. Miller-Klein, SSA Acoustics LLP
3:00 – 3:20
Large Industrial Air Moving Devices
Geoff Sheard, AGS Consulting LLC and Air
Movement and Control Association (AMCA) Board of Directors
3:20 – 3:40
Industrial Power Generation Equipment
Jim Barnes, Acentech Incorporated
3:40 – 4:00
BREAK
4:00 – 4.20
Advanced Noise Control Technology for Electrical Power
Generator Sets
Shashikant More, Cummins, Inc
4:20 – 4:40
Industrial Motors: History of Noise Control with Costs and
Benefits
Arno Bommer, Collaboration in Science and Technology, Inc.
4:40 – 5:00
Compressor Noise
Mike Lucas, Ingersoll Rand, Inc.
OCTOBER 07 PROGRAM
Commercial and Industrial Products (Continued)
8:30 – 9:00
Opening Remarks
Adnan Akay, Workshop Co-chair
Robert Hellweg, Workshop Co-chair
Eric Wood, Workshop Co-chair
9:00 – 9:20
Power and Distribution Transformer Noise
Ramsis Girgis, ABB, Inc.
9:20 – 9:40
Valve and Piping Noise
Allen Fagerlund, Fisher Controls, and Eric Wood, Acentech
Incorporated.
9:40 – 10:00
Noise From Gear Drives
Rajendra Singh, The Ohio State University
A-3
10:00 – 10:20
BREAK
10:20 – 10:40
Engineering Quieter Off-road Vehicles:
Construction, Demolition, Mining, Forestry, Agriculture, and
Grounds Care
Karl B. Washburn, RSG, and Eric W. Wood, Acentech Incorporated
10:40 – 11:00
Mining Noise Sources and their Control
James K. Thompson, JKT Enterprises
11:00 – 11:20
Natural Gas Pipelines: Noise from Compressor Stations and Other
Sources
Reggie Keith, Hoover-Keith, Inc.
11:20 – 11:40
INCE/USA, the INCE Foundation, and International INCE
Eric Wood and Rajendra Singh
11:40 – 1:00
Lunch in the NAE Cafeteria
1:00 - 1:20
Noise Control Engineering for Military Noise Sources
Kurt Yankaskas, Office of Naval Research
1:20 – 1:40
National and International Noise Emission Standards for
Consumer and Industrial Products
Robert Hellweg, Hellweg Acoustics
1:40 – 2:00
Group Discussion: The Costs, Benefits, and Economics of
Noise Control for Industrial Products
Discussion Leader: Adnan Akay, Workshop Co-Chair
2:00 – 2: 20
Workshop Summary
George Maling, Workshop Co-Chair
2:20 – 3:00
Discussion and Workshop Wrap-Up
A-4
Appendix B
Workshop Attendees
Adnan Akay
Provost
Bilkent University
06800 Ankara, Turkey
+90 312 290 1213
James D. Barnes
Principal Consultant
Noise and Vibration
33 Moulton Street
Cambridge, MA 2138
(617) 499-8018
Mark Connelly
Senior Director, Product Testing
Consumer Reports
101 Truman Ave.
Yonkers, NY 10703
(914) 378-2325; (914) 450-8354
Ramsis S. Girgis
Manager
Research and Development
ASEA BROWN BOVERI
4350 Semple Avenue
St. Louis, MO 63125
(314) 679 - 4803; (314) 409- 7080
Willem M. Beltman
Principal Engineer
Intel Corporation
2111 NE 25th Ave
M/S JF2-86
Hillsboro, OR 97124
(503) 712-1547; (503) 709-7051
Robert D. Hellweg
Hellweg Acoustics
13 Pine Tree Road
Wellesley, MA 02482
(781) 431-9176; (781) 690-0751
Mats S. Bernes
Senior Development Engineer
ABB Inc.
4350 Semple Avenue
St. Louis, MO 63120
KevinM. Herreman
Research Associate/Program Leader
Acoustic Research Center
Owens Corning
2790 Columbus Rd, B75
Granville, OH 43023
(740) 321-6865
David L. Bowen
Principal Consultant and
Director Noise and Vibration Group
Noise and Vibration
33 Moulton Street
Cambridge, MA 2138
(617) 499-8068
Arno S. Bommer
Principal
CSTI acoustics
16155 Park Row Blvd
Suite 150
Houston, TX 77084-6971
(281) 492-2784
Cynthia C. Jara-Almonte
Staff Engineer
Product Engineering
InSinkErator, Div. Emerson Electric
4700 21st Street
Racine, WI 53406
(262) 554-3593; (262) 818-2461
Reggie Keith
Hoover & Keith, Inc.
11391 Meadowglen, Suite D
Houston, TX 77082,
United States
(713) 496-9876
B-1
William W. Lang
29 Hornbeck Ridge
Poughkeepsie, NY 12603
(485) 471-5493
Stephen J. Lind
Acoustic Engineer
Applied Acoustics, Mechanics, and
Packaging
Ingersoll Rand
3600 Pammel Creek Road
Bldg 12-1
La Crosse, WI 54601
(608) 787 4351; (608) 386 1706
Mike Lucas
Ingersoll-Rand
Rotary Compression Div.
P.O. Box 1600
Davidson, NC 28036,
United States
(704) 655-4716
George Maling
Workshop Co-Chair
60 High Head Road
Harpswell, ME 04079
(207) 729-6430
Erik T. Miller-Klein
Associate Partner & Acoustical
Consultant
SSA Acoustics, LLP
222 Etruria St, Suite 100
Seattle, WA 98109
(206) 839-0819; (206) 658-7920
Shashikant More
Group Leader
Acoustics, Global Applied
Technology
Cummins, Inc.
1400 73rd Ave. NE
Minneapolis, MN 55432
(763-528-7121)
Workshop Attendees (cont.)
Wayne E. Morris
Vice President
Technical Operations and Standards
Association of Home Appliance
Manufacturers
1111 19th Street NW, Suite 402
(202) 872-5955 x 313
Matthew A. Nobile
Acoustical Engineer (ret.),
23 Mountain View Road
Poughkeepsie, NY 12603
(845) 454-3009
(914) 475-3578
Robert A. Putnam
Consultant
955 Dyson Drive
Winter Springs, FL 32708
(407) 366-9603;(407) 393-8620
Proctor Reid
Director, Project Office
500 Fifth Street
(202) 334-2815
Anthony G. Sheard
President
AGS Consulting LLC
P.O. Box 79267
Atlanta, GA 30357
(678) 974 9565; (678) 974-9565
Larry N. Will
Vice President Engineering (ret.)
ECHO Inc.
1182 Staghorn Trail
Nicholson, GA 30565
(479) 256-0282
Rajendra Singh
The Ohio State University
201 West 19th St
Columbus, OH 43210,
United States
(614) 292-9044
Jason A. Williams
500 Fifth Street
Washington, VA 20001
(202) 334-1597
Shung (Sue) H. Sung
Independent Consultant
4178 Drexel Dr.
Troy, MI 48098
(248) 641-7026; (248) 705-3427
James K. Thompson
JKT Enterprises
3962 Polly Court
Williamsburg, VA 23188
(412) 228-8029; (412) 228-8029
B-2
Eric W. Wood
Principal Consultant
Noise and Vibration
33 Moulton Street
Cambridge, MA 02138
(617) 499-8034
Kurt Yankaskas
NIHL Program Officer
Office of Naval Research (ONR
342)
875 North Randolph Street
Arlington, VA 22203
(703) 696-6999
Appendix C
Acronyms, Abbreviations and Units
AHAM
A&E
AHRI
AI
AMCA
ANSI
ARI
ASA
ASHRAE
ASME
ASSE
ASTM
ATC
BEA
B&K
CAD
CAETS
CAGI
CDC
CE
CFD
CG47
CMM
CMU
CPCB
CR
dB
dB(A)
DDG51
ECMA
EPA
EU
FCTP
FEA
FERC
FWD
GM
HVAC
Association of Home Appliance Manufacturers
Architect and Engineer
Air-conditioning, Heating, and Refrigeration Institute, formerly ARI
Articulation Index
Air Movement and Control Association
American National Standards Institute
American Refrigeration Institute, predecessor to AHRI
Acoustical Society of America
American Society of Heating, Refrigerating and Air-Conditioning Engineers
American Society of Mechanical Engineers
American Society of Sanitary Engineering
American Society of Testing and Materials
Acoustical Technology Center (Cummins)
Boundary Element Analysis
Brüel & Kjær
Computer Aided Design
International Council of Academies of Engineering and Technological Sciences
Compressed Air Gas Institute
Centers for Disease Control and Prevention
Conformité Européenne, a mark indicating conformity with EU regulations
Computational Fluid Dynamics
Class of US warship
Continuous mining machine
Concrete Masonry Unit
Central Pollution Control Board, India
Consumer Reports
Decibel, a logarithmic unit of measurement in acoustics
Decibels of an A-weighted sound level accounting for human perception of sounds
at low-, mid-, and high frequencies
Class of US warship
Ecma International, originally the European Computer Manufacturers Association
Environmental Protection Agency
European Union
I-INCE Future Congress Technical Planners
Finite Element Analysis
Federal Energy Regulatory Commission
Food waste disposers
General Motors
Heating, ventilation, and air-conditioning
C-1
Hz
IEC
IES
IgCG
I-INCE
INCE/USA
ISO
IT
ITI
KBIS
LDN Ldn
LOA
MPH
MSHA
MWe
NAE
NASA
NCEJ
NEMA
NIHL
NIOSH
NNI
NREL
ODP
OLOA
ONR
OSHA
PAS
PC
PEL
PNR
SPL
SQ
RPM
TC
TEFC
TL
TQA
TWA
USGBC
VA
VFD
WOT
WPII
The unit of frequency
International Electrotechnical Commission
Illuminating Enginering Society
International Green Construction Code
International Institute of Noise Control Engineering www.i-ince.org
Institute of Noise Control Engineering of the USA www.inceusa.org
International Organization for Standardization
Information Technology
Information Technology Industry Council
Kitchen and Bath Industry Show
Day-night Sound Level
Line of action
Miles per hour
Mine Safety and Health Administration
Megawatts of electrical energy
National Aeronautics and Space Administration
Noise Control Engineering Journal
National Electrical Manufacturers Association
Noise-Induced Hearing Loss
National Institute for Occupational Safety and Health
Noise/News International
National Renewable Energy Laboratory
Open drip-proof motor enclosure type
Off line of action
Office of Naval Research
Occupational Safety and Health Administration
Publicly Available Specification
Personal Computer
Permissible exposure level
Product Noise Rating
Sound Pressure Level
Sound Quality.
Revolutions per minute
Technical Committee
Totally enclosed fan-cooled motor type
Sound Transmission Loss of a Building Element
Technology for a Quieter America
Time weighted average
U.S. Green Building Council
Veterans Administration
Variable Frequency Drive
Wide Open Throttle
Weather Protected II motor enclosure type
C-2
This report, Engineering a Quieter America, describes
progress on consumer and industrial product noise reduction

Engineering a Quieter America - Institute of Noise Control Engineering

Transcription

Similar documents

theBoom "O"

Epiphanies

March: Stock Car Racing Noise – Conflicts and Feasible Controls

Pantallas Acusticas Pared Verde (EN)

Fosi Vegue - Cosmos Arles Books

August 10, 2016 Danny Page Valecraft Homes Ltd. / Jean

Low Frequency Noise Induced Vibration of Housing Structure–

code on noise levels

Groove Tubes Specifications

NFPA 1500