6.9 AIRCRAFT NOISE CRITERIA

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The noise of automobile and truck traffic along a freeway is relatively uniform,

with a few highs and lows in the noise level. On the other hand, the

noise due to the fly-over of aircraft from an airport is neither constant nor

uniform, even near the airport. Some large airports have takeoffs and landings

as frequently as one every minute or two, whereas smaller airports may

have only one or two takeoffs and/or landings each hour. The intrusive

noise of the aircraft may be as much as 30–40 dBA higher than the ambient

noise, in contrast to ground traffic noise. The intrusive noise for aircraft is

often more annoying than the more steady ground traffic noise, so different

methods have been examined to determine the effect of aircraft noise.

Acoustic Criteria 255

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6.9.1 Perceived Noise Level

The perceived noise level, LPN, was developed as a single-number rating of

annoyance to noise, or aircraft noise, in particular (Kryter, 1959). The

perceived noise level is developed from contours of equal perceived ‘‘noisiness’’

(Kryter and Pearsons, 1963). The units for the equal ‘‘noisiness’’

contours is called noys, in analogy with an older procedure of determining

contours for equal ‘‘loudness’’ in sones (Fletcher and Munson, 1933;

Stevens, 1972). The numerical values of the noys are selected such that a

noise of 4 noys is perceived as four times as ‘‘noisy’’ as a noise of 1 noy. The

conversion data needed for converting from octave band sound pressure

level measurements to an effective noy value are given in Table 6-20

(Pinto, 1962).

The procedure to obtain an effective perceived noise level, LEPN,

dB(PN), from experimental octave band sound pressure level data is as

follows. First, the octave band data is converted to noys using Table 6-20.

Next, the effective noy value Ne is calculated from the following expression:

Ne ј 0:3_Nj ю 0:7Nmax (6-13)

256 Chapter 6

TABLE 6-20 Contours of Equal Noisiness N, in noys

N, noys

Octave band center frequency, Hz

63 125 250 500 1,000 2,000 4,000 8,000

1 60 51 44 40 40 32 29 37

2 67 59 53 50 50 42 39 44

3 72 64 59 56 56 50 44 49

5 77 71 66 63 63 55 52 57

10 85 79 75 73 73 65 62 67

15 90 85 81 79 79 71 68 73

20 94 89 85 83 83 75 72 77

30 100 95 91 89 89 81 78 83

40 104 99 95 93 93 87 82 87

50 108 103 99 96 96 89 86 91

60 110 105 101 99 99 91 88 93

80 114 109 105 103 103 96 93 98

100 117.5 112.5 108.5 106.5 106.5 99 96 101

150 123 118 114 112 112 105 102 107

200 127.4 122.4 119.4 116.4 116.4 109 106 111

300 133.3 128.3 124.3 122.3 122.3 115 112 117

Source: Pinto (1962).

Copyright © 2003 Marcel Dekker, Inc.

The first term is the sum of the noy values for the octave bands, and Nmax

is the largest noy value in all of the octave bands. Finally, the effective

perceived noise level, LEPN, is determined from the following relationship:

LEPN ј 40 ю

10log10 Ne

log10р2Ю

(6-14)

It is noted that an increase of 10 dB(PN) is equivalent to a doubling of the

noisiness in noys.

Example 6-9. The sound level spectrum for a single fly-over at a particular

location around an airport is given in Table 6-21. Determine the effective

perceived noise level for the noise.

The noisiness values corresponding to each octave band sound pressure

level are determined from Table 6-20 and listed in Table 6-21. The

largest noy value or Nmax value is 74 noy; this occurs in the 250 Hz octave

band.

The effective noisiness is calculated from Eq. (6-13):

Ne ј р0:3Юр24 ю 47 ю 74 ю 56ю_ _ _Ююр0:7Юр74Ю ј р0:3Юр327Ю ю 51:8

Ne ј 149:9 noy

The effective perceived noise level is found from Eq. (6-14):

LEPN ј 40 ю

10 log10р149:9Ю

log10р2Ю ј 40 ю 72:2 ј 112:2dBрPNЮ

6.9.2 Noise Exposure Forecast

The noise exposure forecast (NEF) was developed to determine the land-use

compatibility around a commercial (not military) airport with the noise

generated by the aircraft using the airport (Galloway and Bishop, 1970).

The aircraft noise is usually much more significant than any other noise

source for those people living in the vicinity of the airport.

Acoustic Criteria 257

TABLE 6-21 Data for Example 6-9

Octave band center frequency, Hz

63 125 250 500 1,000 2,000 4,000 8,000

Lp(OB), dB 97 102 104 98 90 85 80 76

Nj , noy 24 47 74a 56 32 40 35 19

aNmax value.

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For a specific class of aircraft (i) on one of the flight paths р jЮ of the

airport, the noise exposure forecast, NEFрi; jЮ, is related to the effective

perceived noise level, LEPNрi; jЮ, and the number of daytime and nighttime

flights, ND and NN. A landing is considered as one ‘‘flight,’’ and a takeoff is

considered as another ‘‘flight’’ in determining the NEF:

NEFрi; jЮ ј LEPNрi; jЮю10 log10ЅNDрi; jЮю16:67NNрi; jЮ__88 (6-15)

The value of NDрi; jЮ is the number of flights between 7:00 a.m. and 10:00

p.m. (daytime), and NNрi; jЮ is the number of flights between 10:00 p.m. and

7:00 a.m. (nighttime), for a particular class of aircraft (i) and a specific flight

path ( j). The factor 16.67 arises fromthe fact that the ratio of daytime hours

to nighttime hours is р15=9Ю ј 1:667, and the noise during the nighttime

hours is weighted as 10 times as important as the daytime noise. The constant

88 is arbitrary; however, it was introduced to avoid confusion between

the NEF and the composite noise rating, used previously for rating aircraft

noise effects.

Values for the effective perceived noise level for various types of aircraft

and the detailed method for calculation of this parameter from measurements

are outlined in the literature (Pearsons and Bennett, 1974).

The NEF value at a specific location adjacent to the airport is found

by adding (energywise) the NEFрi; jЮ for each class of aircraft along each

flight path:

NEF ј 10log10

X

i

X

j

10NEFрi;jЮ=10

" #

(6-16)

For a rough approximation (within 3 dBA), the NEF can be calculated

from measured values of the day–night level (EPA, 1974):

NEF _ LDN _35 (6-17)

Noise exposure forecast contours have been used by HUD in evaluating

prospective land use around airports. The report on the determination of

the NEF contours is usually included in environmental impact studies dealing

with the noise from the aircraft operations around an airport area.

Representative land-use compatibility recommendations are given in

Table 6-22. The criteria of the U.S. Department of Housing and Urban

Development (HUD) are shown in Table 6-23 (HUD, 1971).

The detailed construction of the NEF contours for a specific airport is

a time-consuming process. An approximate procedure has been developed

to estimate the location of the NEF-30 and NEF-40 contours, based on the

flight schedules for the airport (HUD, 1971). The dimensions of the approximate

NEF-30 and NEF-40 contours are illustrated in Fig. 6-4. The numer-

258 Chapter 6

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Acoustic Criteria 259

TABLE 6-22 Land-Use Compatibility as a Function of

the Noise Exposure Forecast (NEF)

Land use

NEF

<24 24–30 30–40 >40

Residential S S Qa U

Commercial; industrial S S S U

Hotels, offices, public buildings S S Qb U

Schools, hospitals, churches S Qb U U

Theaters, auditoriums Qc Qb U U

S ј satisfactory; Q ј questionable; U ј unsatisfactory.

aIndividuals may complain, and some may complain vigorously.

New single-family dwelling construction should be avoided.

Noise control features must be included in the building design

for apartment buildings.

bConstruction should be avoided unless a detailed analysis of

noise control requirements is made and the building design

contains the required noise control features.

cA detailed noise analysis is required for any auditorium where

music is to be played.

Source: HUD (1971).

TABLE 6-23 HUD Site Acceptability Categories as Related to Airport Noise

Category Location of the site from the runway center point

Clearly acceptable Outside the NEF-30 controur, at a distance equal to

or greater than the distance between the NEF-30

and NEF-40 contours

Normally acceptable Outside the NEF-30 contour, at a distance less than

the distance between the NEF-30 and NEF-40

contours

Normally acceptable Between the NEF-30 and NEF-40 contours

Clearly unacceptable Within the NEF-40 contour

Source: HUD (1971).

Copyright © 2003 Marcel Dekker, Inc.

ical values of the dimensions L and W are given in Table 6-24. The number

of ‘‘effective’’ flights considers the weighting of noise due to the nighttime

flights:

NEF ј ND ю 16:67NN (6-18)

The application of this approximate procedure is illustrated in the following

example.

It has been observed (Beranek, 1971, p. 583) that the simplified or

approximate procedure is conservative; i.e., the NEF contours according

to the approximate method are larger than those determined through a

more detailed analysis. For this reason, the simplified approach should be

260 Chapter 6

FIGURE 6-4 Description of dimensions used to determine the approximate location

of the NEF-30 and NEF-40 contours. (From HUD, 1971.)

TABLE 6-24 Dimensions for NEF Contour

Approximation

Effective number

of flights, NEF

a

NEF-30 NEF-40

W L W L

0–50 1000 ft 1 mile 0 0

(305 m) (1.6 km)

50–500 0.5 mile 3 miles 1000 ft 1 mile

(0.8 km) (4.8 km) (305 m) (1.6 km)

500–1,300 1.5 mile 6 miles 2000 ft 2.5 miles

(2.4 km) (9.7 km) (610 m) (4.0 km)

>1,300 2 miles 10 miles 3000 ft 4 miles

(3.2 km) (16.1 km) (915 m) (6.4 km)

aThe effective number of flights NEF ј ND ю 16:67NN

Source: HUD (1971).

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used only for preliminary planning, and the detailed analysis should be

utilized for more detailed planning purposes (Schultz, 1970).

Example 6-10. A small airport has two main runways: (a) an east–west

runway, which is 3 miles (4.83 km) long, and (b) a north–south runway,

which is 2 miles (3.22 km) long. The runways cross at a distance of 0.75

miles (1.21 km) from the west end of the east–west runway and 0.75 miles

(1.21 km) from the south end of the north–south runway, as shown in Fig.

6-5. There are 90 daytime flights (takeoffs plus landings) and 12 nighttime

flights during each 24-hour period. Determine the location of the NEF-30

Acoustic Criteria 261

FIGURE 6-5 Diagram for Example 6-10.

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and NEF-40 contours, using the approximate method. Also, determine the

limit for the HUD clearly acceptable category for land use.

The equivalent number of flights is found from Eq. (6-18):

NEF ј 90юр16:67Юр12Ю ј 90ю200 ј 290 flights

The dimensions for the NEF contours are found from Table 6-24:

NEF-40: L ј 1 mile (1.6 km) andW ј 1000 ft (305 m)

NEF-30: L ј 3 miles (4.8 km) andW ј 0:5 mile (0.8 km)

These contours are shown in Fig. 6-5.

The limiting line for the HUD ‘‘clearly acceptable’’ category is found.

The difference between the NEF-30 and NEF-40 contours is as follows:

_L ј 3 _ 1 ј 2miles р3:2kmЮ

_W ј 2640 _ 1000 ј 1640 ft ј 0:311 mile р0:500 kmЮ

The dimensions of the limiting line (measured from the runway) are as

follows:

L ј 3 ю 2 ј 5 miles р8:0kmЮ

W ј 0:50 ю 0:311 ј 0:811 miles ј 4280 ft р1:30kmЮ

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