What are the acoustical barriers to learning?

Classroom Acoustics Seminar
Removing Acoustical Barriers to Learning
Building Confidence:
From Sustainable Policy to Practice
UC Santa Barbara June 21 2004
David Lubman, FASA, Acoustical Consultant
14301 Middletown Lane Westminster, CA 92683
Voice/fax 714/373-3050, [email protected]
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Abstract
America is rediscovering the importance of good
acoustics to learning! Through interdisciplinary
cooperation, the noise, acoustics and hearing
communities developed the first American
standard for classroom acoustics, ANSI S12.602002. Proponents have convincingly shown that
attention to the acoustical design of schools and
classrooms can significantly boost student
achievement, improve student behavior, increase
social inclusiveness, and aid teacher retention.
continued
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Abstract … continued
Advocates believe that the modest costs for good
acoustics are returned to the community through
educational benefits. Everyone benefits from
good acoustics, but it is of inestimable
importance for persons with hearing, language,
or learning disabilities.
Leverage your standing as a building design
professional by becoming the ambassador for
good classroom acoustics in your community.
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Outline
Introductory film
Why is good acoustics important to learning?
Acoustics and Universal Design
What is “good” classroom acoustics?
What is the ANSI Standard for classroom acoustics?
What does it sound like?
Why is an acoustic standard needed?
What is the evidence for improved student achievement?
Key elements of the ANSI Standard
Costs and cost-benefits
Summary
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ANSI S12.60-2002
AMERICAN NATIONAL STANDARD
ACOUSTICAL PERFORMANCE
CRITERIA, DESIGN REQUIREMENTS, AND
GUIDELINES FOR SCHOOLS
Accredited Standards Committee S12, Noise
Available at http://asa.aip.org/classroom.html
The ANSI Standard
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Available free at http://asa.aip.org/classroom/booklet.html
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Available at low cost at http://asa.aip.org/classroom/booklet.html
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Why is acoustics important to learning
Speech communication is an important part of the
learning process
Students and teachers need good acoustics to
understand and convey spoken messages
Young students are still developing language skills
Many disabled students in classrooms
– Disabilities of language, hearing, learning, etc.
– Special education facilities are expensive
– More disabled students must be mainstreamed
Many adult students and teachers have needs similar to
disabled
Why Classroom Acoustics is Important
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Why acoustics is important to
children’s learning?
Kids are more vulnerable to poor acoustics than adults.
– Kids who must listen & learn in noise may sacrifice a year or more in
educational attainment.
– Engagement in learning is longer and deeper with good acoustics
Teachers have more verbal exchanges with students in
classrooms with good acoustics
Speech intelligibility research shows that
– HOH kids lag peers in educational attainment
As many as 1/3 of kids in typical classrooms have extra
sensitivity to poor acoustics due to:
– ESL, HOH, LD, ADD, speech disabilities, etc.
Why Classroom Acoustics is Important
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Everyone benefits from good acoustics
Teachers
– Teachers avoid voice problems from
talking over noise
– Students behave better in quiet
classrooms
Normal students
– Can understand nuanced
communication
– Learning is deeper and remembered
longer
Unmotivated and marginal learners
– Longer engagement in learning
– Fewer dropouts
Why Classroom Acoustics is Important
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ANSI S12.60-2002 is an attempt at acoustical
Universal Design
Definition of Universal
Design
“The design of products
& environments to be
usable by all people,
to the greatest extent
possible, without the
need for adaptation or
specialized design”
Good Classroom Acoustics as Universal Design
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Principles of Universal Design
Design is useful and marketable to people with diverse abilities
– Avoids stigmatizing users
Flexibility in use
– Design accommodates a wide range of preferences and abilities
Perceptible information
– Design communicates necessary information effectively to the user,
regardless of ambient conditions or the user's sensory abilities.
• Provide compatibility with a variety of techniques or devices used
by people with sensory limitations.
Tolerance for error
– Design minimizes hazards and adverse consequences of accidental
or unintended actions
Low physical effort
– Can be used efficiently, comfortably & with a minimum of fatigue
Good Classroom Acoustics as Universal Design
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Hearing impairments compound the
impact of poor acoustics
Almost 20% of K-12 kids have
significant hearing loss (HL)
on any given school day
Listeners with HL are more
adversely impacted by
background noise and
reverberation than normal
listeners
The most prevalent form of
HL, sensori-neural HL, is
characterized by the loss of
high frequency hearing.
Why Classroom Acoustics is Important
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Many K-12 students are English
Language Learners
In the Los Angeles Unified School District over 2/3
of students are non-native English speakers
Many large cities have similar mixed compositions
The ability to hear is a prerequisite for learning to
speak and read
Many teachers are non-native English speakers
A higher quality acoustic channel is needed for
intelligible communication with accented speech
Why Classroom Acoustics is Important
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Why learning requires better acoustics
Learning confronts students with unfamiliar material
– Unfamiliar words are harder to hear than familiar words
– Unfamiliar accents are harder to understand than
familiar accents
– Unfamiliar concepts harder to learn with poor listening
conditions
Learners have less knowledge to “fill in the blanks”
Poor listening conditions cause stress
– It is harder to learn under stressful conditions
– Shorter learning engagement under stressful listening
conditions
– Learning may require sustained attention
Why Classroom Acoustics is Important
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Key elements for good classroom acoustics
Low noise level.
– LA in decibels, or dB
Low reverberation time,
– RT, seconds.
High sound isolation.
– Sound Transmission Class, STC
– Impact Insulation Class, IIC
These topics are covered in 3 ASA publications
Acoustical barriers to learning
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Criteria in ANSI S12.60-2002
Achieve a speech-to-noise ratio of at least 15 dB
– Unoccupied classroom noise level must not
exceed 35 dBA
– Reverberation time must not exceed 0.6 to 0.7
sec at mid frequencies
The ANSI Standard
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Collaborative for High Performance Schools
(CHPS) Acoustic Criteria
Minimum Acoustical Performance (Required)
– “P2.1 Classrooms must have a maximum (unoccupied) noise level
of 45 dBA, with maximum reverberation times of 0.6 second”
Improved Acoustical Performance
(1 Point)
– “5.1 Classrooms must have a maximum (unoccupied) noise level
of 40 dBA, with maximum reverberation times of 0.6 second”
(2 Points)
– “5.2 Classrooms must have a maximum (unoccupied) noise level
of 35 dBA, with maximum reverberation times of 0.6 second”
ANSI S12.60-2002 acoustic criteria are stricter than CHPS!
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How quiet is the 35 dB required for core learning spaces?
Pretty quiet!
– Corresponds to fairly typical suburban living room with no activity
Similar to ASHRAE guidelines for conference rooms (NC 25)
This low noise level can be achieved with close attention to:
Quiet HVAC
– No wall mounted units or conventional unit ventilators
– Low airspeed ventilation
– Careful selection of HVAC components and layout
Sound insulating walls and floor/ceiling assemblies
If site is noisy special attention may be needed for
– Building orientations and room layouts (noise shielding)
– Selection of noise insulating building facades, roofs, entryways …
– Higher STC rated exterior doors and windows, inc. gaskets and seals
The ANSI Standard
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What does speech corrupted by noise
sound like in back row of classroom?
Speech samples demonstrating
Uncorrupted speech (no noise)
High (15 dB) speech-to-noise ratio
(Minimum goal of ANSI standard)
Low (5 dB) speech-to-noise ratio
– (close to CHPS 45 dBA max criterion)
Very Low (0 dB) speech-to-noise ratio
(Outmoded 50 dBA criterion)
What It Sounds Like
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Simulation of high frequency sensori-neural
hearing loss (no noise, no reverberation)
Normal hearing
SN Hearing loss above 2000 Hz
SN Hearing Loss above 1000 Hz
.
SN Hearing Loss above 500 Hz
Low-pass filtered speech samples from NASA CD
What It Sounds Like
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Reverberated Speech Samples
Dry speech (no reverberation)
0.6 second reverb. time
1.3 second reverb. time
5.0 second reverb. time
Reverberated samples from www.mcsquared.com
What It Sounds Like
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What is the evidence?
Rationale is discussed in Annex A of ANSI standard
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Educational rationale
Perceptual rationale
Developmental rationale
Speech intelligibility in background noise and reverberation
Children and teacher’s unawareness of selective barriers to learning
Scholastic achievement affected by acoustics
Special susceptibility of children to background noise and reverberation
Hearing impairment
More discussion in Classroom Acoustics II
– Why now? Massive program of new school building/replacement
– Rising interior noise levels due to increasing urban noise and HVAC
– Rising incidence of middle ear infections
Acoustics and Student Achievement
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Sample studies showing impact of poor classroom acoustics
on children’s learning
Lucas
Bronzaft
Evans & Maxwell
Crandell & Smaldino
Acoustics and Student Achievement
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Lucas (1974/81) (Steady street traffic noise)
Im pact of Str e e t T r affic No is e on
Acad e m ic Achie ve m e nt
( J . Luc a s e t a l, FH WA / C A / D OH S - 8 1 / 0 1 , S e pt 1 9 8 1 )
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Sixt h g rad e st ud ent s
8
6
Third g rad e st ud ent s
4
2
35
55
75
C - W e i g ht e d A mb i e nt N o i s e Le v e l , d B
( A - w e i g ht e d l e v e l s a b o ut 1 4 d B l o w e r )
Acoustics and Student Achievement
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Bronzaft & McCarthy (1975)
(Intermittent noise from elevated trains)
Grade equivalent Reading Score
R e a d in g S c o r e V s Tr a in N o is e
B r o n z a f t & M c Ca r th y ( 1 9 7 5 )
10
8
Q u ie t R o o ms
( m e a n + /- 1 s td d e v )
6
4
No is y Ro o m s
( m e a n + /- 1 s td d e v )
2
2
3
4
5
6
Grade
Acoustics and Student Achievement
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Summary
Excessive background noise and reverberation are barriers to
learning in classrooms.
Without acoustic design standards, new classrooms will continue
to build-in acoustic barrier to learning.
The CHPS acoustic guideline is a modest step forward
The new ANSI classroom acoustic standard developed by a
broad W/G is preferable for good learning
Good acoustics is cost-effective, especially when it can be
included in “green building” design requirements.
It’s the right thing to do for children’s education and a wise
investment in our children’s future.
ANSI S12.60-2002 promotes universal acoustical design
Wrapup
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THANK YOU!
We hope you could hear us
APPENDIX
Costs
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Building and Construction Costs are a small part of
the cost of K-12 Education
$300M is spent nation-wide on education in K-12 school
buildings
Construction cost <10% of total education investment in
school bldg.
– Biggest cost: education programs.
Typical cost for good acoustics < 1% or 2% of bldg costs
Less than 0.1 or 0.2% of cost of K-12 education
Costs repaid by benefits of good acoustics.
– Less failure, less stress, greater inclusiveness, better
student behavior, deeper learning.
What it Costs
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Building construction cost increase for good
acoustics
Overall increase estimated to range from 0.5% to 8%
– Cost increase vary widely.
Cost for quieter HVAC ranges from 0.3% to 6%
– Least for central systems
– Greatest for upgrade from wall-mounted HVAC.
Cost for better sound absorbing treatment: 0.2%
Cost for sound rated windows( if needed): 2%
Cost for better sound insulating walls and floors
– STC 45 $5.90/sq ft (mean + std dev)
– STC 50 $6.50/sq ft “
– STC 53 $6.90/sq ft “
– STC 60 $7.80/sq ft “
– Cost estimates from current (2003) published data
What it Costs
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Current Method for Estimating Costs of Good
Acoustics Is Flawed
Does not count costs of bad acoustics
– Reduced engagement in learning, higher stress levels
– High absenteeism, burnout, truancy
– Discouraged & disruptive students, dropouts, crime
– Wasted education dollars (est annual $7K/student in
year 2000)
Does not count $ benefits of good acoustics!
– What is it worth to hear all of the lecture?
– What is the dollar value of more effective education?
Cost benefits
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Guidelines for school acoustics
neglected in the past
Until the advent of ANSI S12.60-2002, no widely-accepted acoustical
guidelines for US schools
Knudsen and Harris got it right in “Acoustical Designing in Architecture”
(1951) available from the ASA
Schools ignored Knudsen & Harris’s good advice, leaving acoustical
considerations vital for learning to architects
Architects allowed HVAC designers set noise guidelines for schools
ASHRAE* guidelines were very wide, reflecting educator indifference
One result was the “open-plan classroom” design fad of the 1970s
ASHRAE guidelines now tightened - consistent with ANSI Standard
*American Society for Heating Refrigeration & Air Conditioning Engineering
Why is a classroom acoustic standard needed?
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Poor classroom acoustics – widespread,
ignored, & growing
No wide-scale national study has been made, but a
GAO Survey: Environmental Conditions in Public K12 Schools (1995) found:
– "Acoustics for noise control" was the most unsatisfactory
environmental condition reported, affecting 28% of classrooms
nationally (34% in Calif)
An estimated 400,000 NEW students enter schools
throughout the U.S. each year requiring thousands of
NEW classrooms!
The number of new classrooms with poor acoustics will
continue to grow without remedial action!
Why is a classroom acoustic standard needed?
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Acoustical Gap in School Building Codes
Building codes require that learning spaces be adequately lighted and
ventilated.
Until recently, no acoustical code provisions existed for schools,
where verbal communication is vital.
The design community can help to eliminate this design gap.
An inconsistent set of new c.a. standards has begun to emerge
Countertrend: a partial list of governmental entities with acoustical
requirements for schools include:
- Washington D.C.
- State of New Jersey
- State of Washington
- State of Minnesota
- NYC schools
Why is a classroom acoustic standard needed?
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What are the acoustical barriers to learning?
Background Noise from
– Internal building equipment inside classrooms such as
HVAC and educational appliances
– Adjacent rooms that pass through internal walls, floors
or ceilings.
– Exterior transportation or industrial sources, and
playgrounds
Reverberation due to
– inadequate sound absorption on classroom ceilings,
walls, and floors
Acoustical barriers to learning
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Cost Benefits of Good
Classroom Acoustics
Cost benefits
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Cost savings for preventing a child failure
Some children fail because they don’t hear enough of the
lesson to remain engaged in learning
Problem is more severe for ESL students and poorly
motivated students
Consider savings if better acoustics prevents even one
student from dropping out.
Average annual cost of education was $7900/K-12
student in 1999-2000
School system saves $7900 and reduces overcrowding
each time a dropout is prevented.
Cost benefits
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Good C. A. Reduces the Number of Children
Receiving Costly Special Education Services
Excess annual cost for educating children with
hearing impairments averaged $4980 per child
(Colorado, ‘93)
1.05 Million hearing impaired (HI) & 2.68M
speech or language impaired (SLI) school-age
students received Special Education services in
1996-97 (IDEA 20th Ann Rpt)
Cost benefits
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Cost Savings for Fewer Children Receiving
Special Education Services
One study reports a 10% reduction of students receiving
special education services after 3 years of improved
acoustical access to education.
Savings predicted for acoustically fit schools is
$523M/year for HI students alone.
Savings for combined HI and SLI students after 3 years is
$1.83 B/year.
This offsets the initial cost of good acoustics!
Cost benefits
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What Is the Lifetime $ Worth of an Acoustically
Good Classroom?
Assumptions:
– Education in classrooms with good acoustics
increases average lifetime earnings by 1%.
– Lifetime annual earning averages $30K/year.
– Occupational lifetime of 40 years.
Conclusion I:
Good acoustics increases earnings by
$12K/person.
Cost benefits
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What Is the Lifetime $ Worth of an Acoustically
Good Classroom*? Part II
Assume:
– Treated classroom educate an avg 20
students/year & have 20-yr service lives.
Conclusion: Benefit is $4.8M per classroom!
At $10 per treated classroom, the benefit-to-cost.
ratio is 480:1!
Conclusion: Good classroom acoustics is a very
good investment!
Cost benefits
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