presentasi basicnoisecalculations
DESCRIPTION
NOISETRANSCRIPT
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Virginia Tech - Air Transportation Systems Laboratory
CEE 4674Airport Planning and Design
Antonio A. TraniJulio Roa
Sample Airport Noise Computations
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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)
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Sound Exposure Level of Single EventsCalculating Sound Exposure Level (SEL)
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Measuring Single Flyover Events
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Location of Noise Meter
Sound Pressure Level (dBA)
Time (seconds)
Instruments can Record SPL every Second (slow
or fast mode)
Sound Exposure Level (SEL)
IntegrateNumerically
(Using Excel / Matlab)
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Virginia Tech - Air Transportation Systems Laboratory
Measuring Single Flyover Events
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Sound Pressure Level (dBA)
Time (seconds)
Instruments can Record SPL every Second
Sound Exposure Level (SEL)
IntegrateNumerically
(Using Excel / Matlab)
LE = 10log1t0
10L(t )/10 dtt2
t1
LE = Single event noise level (dbA)L(t) = Instantaneous Sound Pressure Level recordedt0 = reference timet1,t2 = times used to perform the numerical integration
In Practice we usea summation to compute
the value of LE
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Measuring Single Flyover Events
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LE = 10log1t0
10Li /10ti=1
N
LE = Single event Sound Exposure Level (SEL) (dbA)Li = Instantaneous Sound Pressure Level recorded at discrete intervals of timet0 = reference timet = is the delta time interval (typically 0.5 to 1 seconds)
LE = 10log1t0
10L(t )/10 dtt2
t1
LE = Single event Sound Exposure Level (SEL) (dbA)L(t) = Instantaneous Sound Pressure Level recordedt0 = reference timet1,t2 = times used to perform the numerical integration
Numericalapproximation
of SEL
Sound ExposureLevel (SEL)
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Numerical Example # 1: Single Flyover
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Sound Exposure Level (SEL) calculation
t1 t2
LAmax
LAmax-10 db
A319 landing event in recorded at PUJ in 2012
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Sample Single Flyover Event(Airbus A319 Landing at Punta Cana)
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Sound Exposure Level (SEL)
Calculation using all values of SPL dbA
recorded
Highest Valueof SPL recorded
(known as LAmax)in Casela 240 instrument
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Virginia Tech - Air Transportation Systems Laboratory
Sample Single Flyover Event(Airbus A319 Landing at Punta Cana)
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Sound Exposure Level (SEL)
Calculation using data from LAmax to LAmax -10 db
Highest Valueof SPL recorded
(known as LAmax)in Casela 240 instrument
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Virginia Tech - Air Transportation Systems Laboratory
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
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Measuring Average Sound Levelsover a Long Period of Time
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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.
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Equivalent Steady Sound Level (Leq)
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Leq = 10log1T 10
Li /10ti=1
N
Leq = Equivalent steady sound level (dbA)Li = Instantaneous Sound Pressure Level recorded at discrete intervals of timeT= time period to measure Leqt = is the delta time interval (typically 0.5 to 1 seconds)
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Equivalent Steady Sound Level (Leq)Numerical Example# 2 : Ramp Noise
Data capturedat PUJairport
Data sampledevery second
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Equivalent Steady Sound Level (Leq)Airport Ramp Data
Aircraft arrival
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Equivalent Steady Sound Level (Leq)Airport Ramp Data
Aircraft arrivalto ramp
Shown the recorded valuesbetween 540 to
630 seconds
You want the completearea under the SPL curve
Soun
d Pr
essu
re L
evel
(dB
A)
Time of Event (seconds)
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Virginia Tech - Air Transportation Systems Laboratory
Soun
d Pr
essu
re L
evel
(dB
A)
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Equivalent Steady Sound Level (Leq)Airport Ramp Data
Approximate areaunder the SPL curve
is the sum of the rectangles
Time of Event (seconds)
t = 1 second
t
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Equivalent Steady Sound Level (Leq)Computations using Excel
Calculations of
10Li /10
LE = 10log1T 10
Li /10ti=1
N
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Equivalent Steady Sound Level (Leq)Computations using Excel
Value of Leq
Thousands of recordings
at PUJ airport
LE = 10log1T 10
Li /10ti=1
N
T=2984 seconds
t = 1 second
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Equivalent Steady Sound Level (Leq)Punta Cana Data
Leq value = 78.89 dBA
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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
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Correcting Sound Levels for Night EventsCalculating Day-Night Sound Level (LDN
or DNL)
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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
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From Sound Exposure Level to Day-Night Level
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Sound Pressure
Level (dBA)
Time (seconds)
Background noise at the location can be extracted by readings made during periods of time with no aircraft operations
Single Flyover
Background noise
Average Steady Sound Level(Leq) - Requires further Integration
0 86,400
You know howto calculate SEL now
for these events
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Virginia Tech - Air Transportation Systems Laboratory
Day-Night Average Noise Metric (DNL)
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Sound Pressure Level (dBA)
Time (seconds)
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
Background noise
Day-Night Average(Ldn) - Requires further Integration
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Airport Planning and Design (Antonio A. Trani)
Numerical Example
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Airport Planning and Design (Antonio A. Trani)
LDN = 10log1T 10
(SELi+W )i /10
i=1
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LDN = Day-night Sound Level (dbA)SELi = Sound exposure level associated with the ith flyoverT= 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
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