Air Transport & Noise Pollution:

Atul K Mittalakmittal@civil.iitd.ac.in

Environmental Engineering LaboratoryDepartment of Civil EngineeringIndian Institute of Technology Delhi

Noise:

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Noise is defined as"unwanted sound”

In contrast to otherenvironmental pollution,noise pollution is special in that Personal and subjective judgment is a big part of recognizing asound as noise pollution or not.

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Noise is everywhere

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Basics of Sound:

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Characteristics of SoundPhysical ParametersSound FieldsMeasurements of sound

Characteristics of Sound -- Amplitude:

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P = Pressure Amplitude..

The higher the amplitude, the

higher the sound pressure

levelPressure Amplitude Pmax = maximum deviation of the pressure from atmospheric pressure

P = Pmax sin(kx-wt)

Characteristics of Sound -- Frequency:

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Frequency f = number of pressure fluctuations per second TheFrequency is related to the period:

f = 1/TFrequency is measured in

Hertz (Hz)1 Hz = 1 cycle per second

Characteristics of Sound -- Wavelength:

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Wavelength λ = The distance required for the wave to repeat itself

Wavelength is related to frequency by the speed of sound: λ = c/flow frequency – long wavelengthhigh frequency – short wavelength

Physical Parameters – Sound Pressure:

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Pressure equation: P = Pmax sin(kx-wt)Displacement equation S = Smax cos(kx-wt)

Pmax = (Bk) Smax

WhereB = Bulk modulous of elasticityk = angular wave numberw = angular frequency

If the velocity of sound = V then B = V2pSo Pmax=(V2pk)Smax = (Vpw)Smax

Physical Parameters – Sound Power:

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Kinetic Energy dK of a differential mass of air (dm = pAdx) propogationg the sound wave is

dK = ½ dm Vs2

dE/dt = 2dK/dt = pAVw^2Smax^2sin^2(kx-wt)Average power over a whole number of wavelengths

Power W = (dE/dt)avg = ½pAVw2Smax2

Physical Parameters – Sound Intensity:

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The Intensity of a sound wave is defined as the average rate at which power is transmitted per unit cross sectional area in the direction of travel.

I = ½(pVw2Smax2)or

I = Pmax2/(2pV)

Outdoor Noise Propagation:

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The Sound Intensity

I = Q (P/4pi r^2) or I = P/SWhere

Q = directivityP = PowerS = area (spherical or non-spherical)

Sound levels

Lp ~ Li = Le + 10 log(Q/r^2) - 11

Indoor Noise Propagation:

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The Sound Intensity

I = Q (W/4pi r2) or I = W/SWhere

Q = directivityP = PowerS = area (spherical or non-spherical)

Sound levels

Lp ~ Li = Le + 10 log (1/4pir2 + 4/R)

Where R = room constant

Measurement of Sound:

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A sound level meter (SLM) or a microphone &data acquisition system is used to measure

sound pressure levels

Sound Pressure Level (Decibels):

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Unit of measurement : DecibelDecibel is logarithmic

Decibel dB = 10 log(x/y)Where x – value of any measure

y = reference value of the same measure

Sound Pressure Level Lp(dB) = 10 log (P^2rms/4x10^-10)Sound Intensity Level Li(dB) = 10 log (I/10^-12) Sound Power Level Lw(dB) = 10 log (W/10^-12)

Some Numbers (SPL):

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• Rustling leaves: - 10db• Whisper: 30 db• Normal speech: 60 db• Television: 70 db• Traffic: 75-80 db• Blow dryer: 85 db• Noisy hall: 85 db

• Classroom: 85 db• Stereo: 90 db• Bagpipes: 90-110 db• Power saw: 100 db• Fire cracker: 115-120 db• Rock concert: 120 db• Gunshot/train/jet: 150 db

Mathematics of decibels:

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Decibels are logarithmic, not linear

Cannot simply add, subtract, or average sound levels

We can only add the ‘intensity values’, ‘power values’or the ‘rms values of pressures’

Two sources with equal sound levels increase soundlevel by 3 dB

Example: 90 dB + 90 dB ≠ 180 dB90 dB + 90 dB = 93 dB

Noise Pollution

Sound that is unpleasant and unwanted by the listener because of its bothersome nature, interference with the perception of wanted sound or its harmful physiological and psychological effects

IndustrialVehicularAircraftOthers

Sound LevelsSound levels are measured in units of pressure

Decibels (dB)—each 10 dB indicates a doubling of sound/noise (logarithmic scale)

Types of Noises

ContinuousNear a busy Interstate highway

IntermittentThe approach to an airport runway with aircraft spaced a few minutes apart

ImpulsiveA fireworks explosion, a thunderclap, a vehicle backfire, or a single truck using “jake brakes”

Impulsive noises are the most disturbing to most peopleTransportation creates all three types

Effects

Health experts argue noise pollution in India is a major cause of heart attacks and other stress related illnesses. Most transportation noise in the US is now well below the pain thresholdNoise is much more a quality of life issue than a human health issue

Sleep disturbance is the most common complaint of people annoyed by noise

Probably has some health implicationsStartle or fear is nextSpeech interference is next

Excessive noise can reduce residential property values

How Noise Affects our Ears :

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Health effects of aircraft noise

High levels of aircraft noise that commonly exist near major commercial airports causes:

High blood pressureHearing lossHeart diseasesImmune deficiencyAsthmaOther stress related problems

Noise Regulation:

AMBIENT NOISE STANDARDS: CENTRAL POLLUTION CONTROL BOARD.S.No. Area LeqdB(A)

Day Time* Night Time**

1 Industrial Area 75 70

2 Commercial Area 65 55

3 Residential Area 55 45

4 Silence Zone*** 50 40

* Day Time -- 0600 hour to 2100 hour (15 hours)

** Night time --2100 hour to 0600 hour (09 hours)

*** Areas upto 100 metres around certain premises like hospitals, educational institutions and courts may be declared as silence zones by the competent authority

The Noise Regulation Rules 2000Section 3 of the Environmental Protection Act of 1986.

LOK SABHASTARRED QUESTION NO 398ON 21.08.2000

NOISE MODELING METHODOLOGY

To evaluate the expected noise levels for future conditions

Since future noise levels cannot be directly measured, it is necessary to simulate the expected future condition through noise modeling.

It is the only way that alternative airspace designs can be compared to one another to identify the relative noise effects for each proposal.

Data Req

General Study Data: NIRS requires general information about the study to perform the noisecalculations. Study area information such as the coordinates of the center of the study, the lengthand width of the study area and the altitude ceiling of the study are necessary inputs. Alsorequired is climatologically data such as average headwind speed, average annual temperatureand average annual pressure. Finally, any special regions within the study area need to beidentified.

IIT DELHI STUDY: Aircraft Operation

Predict the noise levels, in Delhi, due to the airports in the city. Noise levels at IIT were monitored in order to cross reference the predictionsAircraft noise is variable and intermittent. It is not continuous as in the case of road traffic noise. There are peak noise levels when aircrafts are flying overhead, or are taking-off and landing at the airports.

Environmental Conditions

Ground conditions may greatly impact noise propagation

Hard ground (e.g. concrete) has little impactMixed ground (e.g. grass and other vegetation) may attenuate noise to some extentSoft ground will absorb a great deal of noise

Wind either blunts the spread of noise or carries it farther, depending on the wind direction and speed; at short distances, wind effects are minor

Environmental ConditionsTemperature

On clear nights, temperatures may actually be lower near the ground and increase with altitude

This leads to an air inversionSounds are trapped near the surface and noises will carry farther near the surface under such circumstances

High ambient air pressure, cold temperatures, and low relative humidity/no precipitation are the best weather conditions for noise propagation

Airport Runway and Configuration Data:

Information specific to airport in the study. The location of each runway, the elevation of the runway ends, and the length of each runway.

Input data for configuration data includes annual percentage use for each operational configuration for each airport within the study. This data includes annual configuration use for the airports and runways use for each of those configurations.

INPUT

Airport settingsLatitude and longitude of the airport referencepoint (decimal degrees)Runway end-point x, y positions relative to thereference point (feet)Airport elevation (feet MSL)Airport average annual day temperature (degreesFahrenheit)Airport average annual day relative humidity(percent)Airport average annual barometric pressure

Population and Grid Location Data:

Users input population centroid identification, location & population

Flight Event/Track Data:

FLIGHT

FLIGHT EVENT FLIGHT TRACK

•Flight identification,•City-pair•Time•Runway•Airframe/engine type

•Geometry of the fight in series of points

•Latitude, •Longitude•Altitude

Aircraft types & Input Database

Aircraft flight operation type Number of flight operations for each of three time periods (day, evening, and night) during an average annual day

an acoustic database of noise vs. power vs. distance (NPD) values

Assumptions

•No military flights land on the airports.•No cargo planes land on the airports.•All flights (national or international) land on IGI Airport only.•Out of the two existing runways only the one that is used mostoften shall be considered.•Flight schedule for one week is fixed and is repeated everyweek.•The weather conditions in every part of the city are constant.•For one whole flight series (e.g. Boeing 737, Boeing 734,Boeing 738) only one representative aircraft (e.g. Boeing 737)will be considered.

Airport Data

Elevation: ............. 777 Feet / 237 MetersIATA: .................. DELICAO: .................. VIDPLatitude: .............. 28°33' 59" NLongitude: ............. 77°6' 11" ERunway 1 Length: ......12500 Feet / 3810 MetersRunway 2 Length: ....... 9229 Feet / 2813 Meters

Exposure Based Contour (SEL)

Metric → Actual (dB) INM Metrics

Day↓ SEL (dB) PNLTM (dB) LAMAX (dB)

Day 1 78 >80 75-80 75-80

Day 2 72 >80 75-80 75-80

Day 3 71 >80 75-80 75-80

Day 4 79 >80 75-80 75-80

Day 5 72 >80 75-80 75-80

Day 6 73 >80 75-80 75-80

Day 7 76 >80 75-80 75-80

Noise Levels at IIT

Noise levels at the selected locations

Metrics → PNLTM (dB) SEL (dB) LAMAX (dB)

Location ↓

IITD 75-80 >85 75-80

V.VIHA 80-85 >85 80-85

AIMS 70-75 >85 70-75

R.G. 40-45 70-75 30-35

LNAGAR 65-70 >85 70-75

R.M.L. 40-45 70-75 35-40

DU.S.C. 55-60 >85 50-55

R.S.TB. 60-65 >85 55-60

C.P. 35-40 65-70 35-40

Noise Levels in Selected CitiesMoEF Study

Cities New Method Standard Method

Day/Night Industrial Commercial Residential

CalcuttaDay

Night7867

8275

79 65

Mumbai DayNight

76 65

7566

7062

Chennai DayNight

71 66

7871

66 48

How to tackle noise from the aircrafts: Solution I: Noise reduction at the

source

•Changing the flight path of the aircrafts at theairport.

•Changing the flight schedule and trying to spreadout the noise evenly throughout the day.

•Using less noisy engines in the aircrafts.•Changing the location of the airport.•Shortening the length of the take off and landing

flight segments.

Solution II: Noise reduction at the target

We can use many kinds of sound barriers to this effect.

These barriers can be further subdivided in two categories: passive and active.

The Web-based program pinpoints a home’s location relative to the aircraft noise contours. Anyone with Internet access can type in a street address and quickly learn if the property is within one of the noise contours.

As of December 31, 2004 total disbursements for 106 schools with executed grant agreements as $252.4 million.

Or Community is outreaching

Aircraft Noise Reduction