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Noise 101 Aircraft Noise Terminology. Ted J. Woosley Director. 2001 Airport Noise Symposium University of California, Berkeley February 2001. What is Noise?. Noise is unwanted sound Noise is temporary Annoyance is subjective. Perception of Sound.

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Noise 101 aircraft noise terminology

Noise 101Aircraft Noise Terminology

Ted J. Woosley

Director

2001 Airport Noise Symposium

University of California, Berkeley

February 2001


What is noise
What is Noise?

  • Noise is unwanted sound

  • Noise is temporary

  • Annoyance is subjective

Noise 101 - University of California, Berkeley


Perception of sound
Perception of Sound

  • How people perceive sound depends on several measurable physical characteristics of the sound:

    • Intensity

    • Frequency Content

    • Changes in Sound Pressure Level

    • Rate of Change in Level

Noise 101 - University of California, Berkeley


Decibels
deciBels

  • Decibels (dB) are the unit of measurement on the loudness scale

  • The decibel scale is logarithmic, not linear

    • Smallest detectable change = 1 dB

    • 3 dB is readily detectable

    • 10 dB seems twice as loud

Noise 101 - University of California, Berkeley



Decibel weightings
Decibel Weightings

Noise 101 - University of California, Berkeley


Decibel addition
Decibel Addition

Twice the energy is equal to 3 dB

Noise 101 - University of California, Berkeley


Noise absorption attenuation
Noise Absorption/Attenuation

  • Air absorbs noise at the rate of 6 dB per doubling of distance (point source)

  • A typical Chicago-area house attenuates outdoor noise:

    • 15 dB with windows open

    • 25 dB with windows closed

Noise 101 - University of California, Berkeley


Rules of thumb
“Rules of Thumb”

  • 3 dB is noticeable to most people

  • Adding two like sounds adds 3 dB increase

  • Double or half the airport operations= +/- 3 dB

  • 10 dB sounds twice as loud or twice as quiet

  • Double or half the distance equates to 6 dB

  • Using DNL, 1 night flight=10 day flights

Noise 101 - University of California, Berkeley


Comparative noise levels db
Comparative Noise Levels (dB)

Saturn rocket 200

Walkman ½ volume 94

MD80 takeoff - 1,500 ft. altitude 85

dialtone 80

talking at 3 feet 65

quiet urban daytime 50

quiet urban nighttime 40

quiet rural nighttime 25

Noise 101 - University of California, Berkeley




Noise metrics
Noise Metrics

  • Lmax - Maximum noise level

  • SEL - Sound exposure Level

  • Leq - Equivalent Sound Level

  • DNL - Day-night average sound level

Noise 101 - University of California, Berkeley


Lmax maximum sound level
LmaxMaximum Sound Level

  • Lmax is the maximum A-weighted sound level for a given event.

Noise 101 - University of California, Berkeley


Sel sound exposure level
SELSound Exposure Level

  • SEL is a measure of the physical energy of the noise event which takes into account both intensity and duration.

  • SEL is typically used to compare noise events of varying durations and intensities.

Noise 101 - University of California, Berkeley


Leq equivalent sound level
LeqEquivalent Sound Level

  • Leq is the steady A-weighted sound level over any specified period.

  • Leq is used to identify the average sound level over a given period of time.

Noise 101 - University of California, Berkeley


Dnl day night average sound level
DNL Day-Night Average Sound Level

  • DNL is a 24-hour time-averaged sound exposure level with a 10 dB nightime (10p-7a) weighting.

  • DNL = Total Daytime Sound Energy + 10 times Total Nighttime Sound Energy divided by Time (in seconds)

  • DNL is the metric of choice in the airport world. It is used to define noise contours of equal exposure.

  • All Federal agencies have adopted DNL as the metric for airport noise analysis.

Noise 101 - University of California, Berkeley


Comparison of different sounds
Comparison of Different Sounds

SEL=100 dB

Leq=105

Event Duration=.3 sec.

SEL=100 dB

Leq=82

Event Duration= 70 sec.

SEL=100 dB

Leq=71

Event Duration= 900sec.

Noise 101 - University of California, Berkeley


Integrated noise model inm and noise contours
Integrated Noise Model (INM)and Noise Contours

  • The required tool for calculation of aircraft noise contours in studies seeking to make noise mitigation eligible for Airport Improvement Program (AIP) or Passenger Facility Charge (PFC) funding.

    Ingredients – INM

  • Airport information - runways, temperature, airport altitude

  • Where aircraft fly - flight tracks (definitions and usage)

  • What aircraft are flown - fleet mix data

  • How often they fly - operations levels – day/night (night=10dB penalty with DNL)

  • What engines are used - hush kit information

  • Where they fly from - runway usage

  • When they fly - time-of-day characteristics

  • How they are flown - climb/descent profiles

  • Where they fly to - performance data

  • Output includes Noise contours connecting points of equal noise exposure (typically 65, 70, 75 DNL), Tabular information, Noise levels at specific locations (grid point analysis)

Noise 101 - University of California, Berkeley


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