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Noise 101: Introduction to Acoustics and Aircraft Noise Terminology

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Noise 101: Introduction to Acoustics and Aircraft Noise Terminology The Shot Heard Round the World Chris Bajdek Harris Miller Miller & Hanson Inc. – PowerPoint PPT presentation

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Title: Noise 101: Introduction to Acoustics and Aircraft Noise Terminology


1
Noise 101Introduction to Acoustics and
Aircraft Noise Terminology
The Shot Heard Round the World
  • Chris Bajdek
  • Harris Miller Miller Hanson Inc.

2
Goals
  • To introduce
  • Aircraft noise terminology
  • Aircraft noise and land use compatibility
  • Application of acoustics to
  • noise mitigation programs in general, and
  • sound insulation programs in particular

3
Topics
  • A-Weighted Decibel, dB(A)
  • Maximum A-Weighted Sound Level, Lmax
  • Equivalent Sound Level, Leq
  • Sound Exposure Level, SEL
  • Day-Night Average Sound Level, DNL
  • Land Use Compatibility with Yearly DNL
  • Noise Level Reduction, NLR

4
A-weighted Sound Pressure Level
  • The human auditory system is not equally
    sensitive to all frequencies
  • To be a useful environmental analysis tool we
    need a way to measure sound the same way the ear
    hears it

A-weighting Correction Levels
  • The A-weighted sound level achieves this goal
  • The EPA has adopted the A-weighted sound level
    for environmental analyses

5
Common A-weighted Sound Levels, in dB
6
Maximum Sound Level (Lmax)
  • Because of the variation in level of a sound
    event, it is often convenient to describe the
    event with its maximum sound level, abbreviated
    as Lmax
  • Accounts only for sound amplitude (A-weighted
    level)
  • Two events may have the same maximum level, but
    much different exposures

Lmax 85
7
Equivalent Sound Level (Leq)
  • A constant sound level equivalent on an energy
    basis of a time varying sound level over the same
    time period
  • Leq is time-averaged
  • Accounts for sound amplitude and time

8
Sound Exposure Level (SEL)
  • A way to describe the noisiness of a complete
    noise event
  • Accounts for sound amplitude (A-weighted level)
  • Accounts for noise event duration

9
Sound Exposure Level (SEL)
10
Day-Night Average Sound Level (DNL)
  • A way to describe the noise dose for a 24-hour
    period
  • Accounts for noise event noisiness (SEL)
  • Accounts for number of noise events
  • Provides an additional weighting factor for
    nighttime operations
  • CNEL includes another weighting factor for
    evening operations

11
Day-Night Average Sound Level (DNL)
  • where
  • Ldn Day/Night Average Sound Level (denoted DNL
    in contour plots)
  • Log10 base 10 logarithm
  • 86,400 number of seconds in a day
  • SEL,j individual Sound Exposure Level readings
    during the day
  • N number of Sound Exposure Level readings
    during the day
  • Wj time of day weighting for the jth aircraft
    passby (10 dB for night)

  • (For CNEL Wj is 4.7 dB for evening)

12
Day-Night Average Sound Level (DNL)
13
Outdoor Ambient DNL at Various Locations
14
DNL Compared to Annoyance
  • Schultz developed accepted dose-response
    relationship in 1970s. FICON re-affirmed, 1992

Source FICON, 1992, Data USAF Armstrong
Laboratory
15
Land Use Compatibility
  • DNL is most widely accepted metric, worldwide
  • Part 150 provides FAA guidelines
  • All land uses compatible below DNL 65 dB
  • FICON reconfirmed in 1992
  • Local responsibility for determining
    acceptability
  • US Dept. of HUD publishes standards for federal
    funding of residential construction
  • Acceptable DNL 65 dB
  • Normally unacceptable DNL 65 to 75 dB (additional
    sound attenuation required)
  • Unacceptable above DNL 75 dB (case-by-case
    conditional approval)

16
FAA Guidelines
  • In the U.S., sound insulation program
  • guidelines are covered under
  • Airport Improvement Program (AIP) Handbook FAA
    Order 5100.38C

Source http//www.faa.gov/airports_airtraffic/ai
rports/aip/aip_handbook/
17
FAA Guidelines for Sound Insulation Effectiveness
  • Residential Structures
  • Achieve interior DNL lt 45 dB
  • Achieve minimum 5 dB improvement in NLR
  • School Sound Insulation Programs
  • Achieve interior Leq,7 lt 45 dB
  • Achieve minimum 5 dB improvement in NLR

18
Noise Level Reduction (NLR)
  • NLR SELoutdoor - SELindoor

19
Goals
  • To introduce
  • Aircraft noise terminology
  • dBA, Lmax, SEL, Leq, and DNL
  • Land use compatibility with aircraft noise
    exposure
  • For residential land use DNL 65 dB (exterior)
  • Application to noise mitigation programs in
    general, and sound insulation programs in
    particular
  • Residential DNL 45 dB (interior) and 5 dB
    improvement
  • Schools Leq 45 dB (interior) and 5 dB
    improvement

20
By the rude bridge that arched the floodTheir
flag to April's breeze unfurledHere once the
embattled farmers stoodand fired the shot heard
round the world.
  • Ralph Waldo Emerson, "Concord Hymn"

21
Questions?
  • Chris Bajdek
  • Harris Miller Miller Hanson Inc.
  • 77 South Bedford Street
  • Burlington, MA 01803
  • 781.229.0707
  • cbajdek_at_hmmh.com
  • www.hmmh.com

22
www.hmmh.com
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