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Table 4-53: Number of People Residing in High Noise Areas Around U.S. Airports^a,b,c

(Within 65 dB DNL noise-level contours)

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KEY: dB = decibels; DNL = day-night sound level; R = revised; N = Not applicable.

^a Noise-level contours are graphical representations of noise levels on a map, similar to elevation contours on a topographic map. Noise-level contours are lines that join points of equal sound levels. Areas between given noise-level contour lines would have a noise level between the two contour values. The U.S. Department of Transportation, Federal Aviation Administration (FAA) has identified DNL 65 dB as the highest threshold of airport noise exposure that is normally compatible with indoor and outdoor activity associated with a variety of land uses, including residential, recreational, schools, and hospitals.

^b Estimates are for areas surrounding airport property of 250 of the largest civil airports with jet operations in the United States. They exclude exposure to aircraft noise within an airport boundary.

^c 1975 exposure estimates were made by the U.S. Environmental Protection Agency. 1980-2003 estimates were made by FAA.

^dAs of 2004, the FAA no longer publishes the number of people exposed to noise. These are now tracked as percent reduction numbers, which were used to compute the exposure values for these years.

SOURCES

Exposure:

1975-2005: U.S. Department of Transportation, Federal Aviation Administration, Office of Environment and Energy (AEE-12), personal communications, Sept. 19, 2002 , Jan. 18, 2004, Mar. 15, 2005 and June 21, 2007. Performance and Accountability Report

Population:

1975-85: U.S. Department of Commerce, Census Bureau, Historical National Population Estimates, Internet site http://www.census.gov/popest/archives/1990s/popclockest.txt as of Mar. 17, 2005.

1990-99: Ibid., National Intercensal Estimates, Internet site http://www.census.gov/popest/archives/EST90INTERCENSAL/US-EST90INT.html as of Mar. 17, 2005.

2000-05: Ibid., Monthly Population Estimates for the United States, Internet site http://www.census.gov/popest/national/NA-EST2004-01.html as of June 19, 2007.