|Year||People (millions)||Percent of U.S. Resident Population||U.S. Resident Population (millions)|
KEY: db=decibels; DNL=day night sound level.
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 anoise level between the two contour values. The U.S. Department of Transportation, Federal Aviation Administration (FAA) has identified FNL 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 airport 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. 1980-99estimates were made by FAA. See the source and accuracy statement for more details on how exposure estimates are made.
SOURCES: Exposure: U.S. Department of Transportation, Federal Aviation Administration, Office of Environment and Energy (AEE-12), personal communications. Population: U.S. Department of Commerce, Census Bureau, Statistical Abstract of the United States 1999 (Washington, DC: 2000), table 2.