(Within 65 dB DNL noise-level contours)
|Year||Exposure||U.S. resident population (millions)|
|People (thousands)||Percent of U.S. resident population|
KEY: dB = decibels; DNL = day-night sound level; R = revised.
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.
1975-2003: U.S. Department of Transportation, Federal Aviation Administration, Office of Environment and Energy (AEE-12), personal communications, Sept. 19, 2002 , Jan. 18, 2004, and Mar. 15, 2005.
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.
2000-2003: Ibid., Monthly Population Estimates for the United States, Internet site http://www.census.gov/popest/national/NA-EST2004-01.html as of Mar. 16, 2005.