CEE 4674 Airport Planning and Design Antonio A. Trani Julio Roa

Transcription

CEE 4674
Airport Planning and Design
Antonio A. Trani
Julio Roa
Sample Airport Noise Computations
Virginia Tech - Air Transportation Systems Laboratory
Topics Covered
•
Calculating SEL (Sound Exposure Level) for single
flyover events
•
Calculating Equivalent Steady Sound Levels (Leq)
•
•
Applicable over longer periods of time
Calculating Day-Night average sound levels (LDN)
•
Leq corrected for night effects (night events are
weighted more than day events)
2
Sound Exposure Level of Single Events
Calculating Sound Exposure Level (SEL)
3
Measuring Single Flyover Events
Instruments can Record
SPL every Second (slow
or fast mode)
Location
of Noise Meter
Sound Pressure
Level (dBA)
Sound Exposure
Level (SEL)
Integrate
Numerically
(Using Excel /
Matlab)
Time (seconds)
4
In Practice we use
⎡ 1 t1 L(t )/10 ⎤
LE = 10log ⎢ ∫ 10
dt ⎥
a summation to compute
t
2
⎣ t0
⎦
the value of LE
LE = Single event noise level (dbA)
L(t) = Instantaneous Sound Pressure Level recorded
t 0 = reference time
t1 ,t 2 = times used to perform the numerical integration
Instruments can Record
SPL every Second
Sound Pressure
Level (dBA)
Sound Exposure
Level (SEL)
Integrate
Numerically
(Using Excel /
Matlab)
Time (seconds)
5
⎡ 1 t1 L(t )/10 ⎤
LE = 10log ⎢ ∫ 10
dt ⎥
t2
t
⎣ 0
⎦
LE = Single event Sound Exposure Level (SEL) (dbA)
L(t) = Instantaneous Sound Pressure Level recorded
t1 ,t 2 = times used to perform the numerical integration
Sound Exposure
Level (SEL)
⎡ 1 N Li /10 ⎤
Numerical
LE = 10log ⎢ ∑10 Δt ⎥
approximation
⎣ t 0 i=1
⎦
of SEL
LE = Single event Sound Exposure Level (SEL) (dbA)
Li = Instantaneous Sound Pressure Level recorded at discrete intervals of time
Δt = is the delta time interval (typically 0.5 to 1 seconds)
6
Numerical Example # 1: Single Flyover
LAmax
LAmax-10 db
A319 landing event in
recorded at PUJ in 2012
t1
t2
Sound Exposure
Level (SEL) calculation
7
Sample Single Flyover Event
(Airbus A319 Landing at Punta Cana)
Highest Value
of SPL recorded
(known as LAmax)
in Casela 240
instrument
Sound Exposure
Level (SEL)
Calculation using all
values of SPL dbA
recorded
8
Sample Single Flyover Event
(Airbus A319 Landing at Punta Cana)
Highest Value
of SPL recorded
(known as LAmax)
in Casela 240
instrument
Sound Exposure
Level (SEL)
Calculation using
data from LAmax
to LAmax -10 db
9
Observation
•
The solution of SEL calculated using the full SPL
history trace recorded was 93.42 dBA
•
The solution of SEL calculated using the time
interval between highest value of SPL recorded and
Lamax -10 dbA was 93.23 dBA
•
The small difference indicates that considering the
time range of values with the peak signal (LAmax
and LAmax -10 dBA) is a very good approximation
10
Measuring Average Sound Levels
over a Long Period of Time
11
Equivalent Sound Level (Leq)
•
Measures the equivalent sound level over a longer
period of time
•
•
Used to measure noise over a long time
Applications:
•
•
Ramp noise at the airport
Runway operation noise etc.
12
Equivalent Steady Sound Level (Leq)
⎡ 1 N Li /10 ⎤
Leq = 10log ⎢ ∑10 Δt ⎥
⎣ T i=1
⎦
Leq = Equivalent steady sound level (dbA)
Li = Instantaneous Sound Pressure Level recorded at discrete intervals of time
T = time period to measure Leq
Δt = is the delta time interval (typically 0.5 to 1 seconds)
13
Numerical Example# 2 : Ramp Noise
Data captured
at PUJ
airport
Data sampled
every second
14
Airport Ramp Data
Aircraft arrival
15
Sound Pressure Level (dBA)
Airport Ramp Data
Shown the recorded values
between 540 to
630 seconds
Aircraft arrival
to ramp
You want the complete
area under the SPL curve
Time of Event (seconds)
16
Airport Ramp Data
Sound Pressure Level (dBA)
Δt = 1 second
Approximate area
under the SPL curve
is the sum of the rectangles
Δt
Time of Event (seconds)
17
Computations using Excel
⎡ 1 N Li /10 ⎤
LE = 10log ⎢ ∑10 Δt ⎥
⎣ T i=1
⎦
Calculations of
Li /10
10
18
Computations using Excel
⎡ 1 N Li /10 ⎤
LE = 10log ⎢ ∑10 Δt ⎥
⎣ T i=1
⎦
Thousands of
recordings
at PUJ airport
T=2984 seconds
Δt = 1 second
Value of Leq
19
Punta Cana Data
Leq value = 78.89 dBA
20
For Discussion
•
The approximation of the area under the curve looks
very crude using rectangles
•
The method shown uses a rectangular integration
method employing the actual observations as the
basis for the height of each rectangle
•
•
Can you improve the solution?
Discuss other numerical methods
21
Correcting Sound Levels for Night Events
Calculating Day-Night Sound Level (LDN
or DNL)
22
Converting from SEL to Day-Night
Averages
•
With known values of SEL for each aircraft
operations we can piece together a series events
throughout the day to estimate the total day-night
average sound levels (DNL) due to aircraft
operations
•
•
However:
Flight operations at night need to be corrected by an
empirical “annoyance factor”
23
From Sound Exposure Level to Day-Night
Level
•
Background noise at the location can be extracted by
readings made during periods of time with no aircraft
operations
Sound
Pressure
Level (dBA)
You know how
to calculate SEL now
for these events
Single Flyover
Average Steady Sound Level
(Leq) - Requires further Integration
Background noise
0
86,400
Time (seconds)
24
Day-Night Average Noise Metric (DNL)
•
•
LDN or DNL is computationally similar to Leq
However, Ldn includes correcting nighttime
operations (10 PM to 7 AM) by a factor of 10 dBA
Sound Pressure
Level (dBA)
Day-Night Average
(Ldn) - Requires further Integration
Background noise
Time (seconds)
25
Numerical Example
Airport Planning and Design (Antonio A. Trani)
26
⎡ 1 N (SELi +W )i /10 ⎤
LDN = 10log ⎢ ∑10
⎥
T
⎣ i=1
⎦
LDN = Day-night Sound Level (dbA)
SELi = Sound exposure level associated with the ith flyover
T = Reference time (86,400 seconds in 24 hrs)
The formula shown only accounts for the noise generated by
aircraft flyovers
If you want the contributions of ground vehicles and other
ramp noise you need to add those noise sources
27
28
29

CEE 4674 Airport Planning and Design Antonio A. Trani Julio Roa

Transcription

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