The Natural History of Foster City, California
by James K. Sayre
a draft manuscript
12 May 2005
Noise
Noise comes from many human inventions, such as leafblowers, automobiles, airplanes and from natural phenomena - such as ocean surf, wind and birdsong. In Foster City, much manmade noise comes from the flow of traffic on major highways such as the Bayshore Freeway, Route 101 and Route 92, the road running from San Mateo across the San Mateo Bridge over to Hayward. San Francisco International Airport (SFO), which lies just seven miles north of Foster City, produces jet plane noise as planes fly over Foster City in their landing paths. The San Carlos Airport, located only two miles south of the closest border of Foster City, which serves general aviation (private planes), also produces some noise in Foster City. Several governmental agencies, including the City and County of San Francisco, have done studies of aircraft noise in the areas around the San Francisco Airport. These studies have produced contours of the hypothetical noise levels experienced by residents in these areas. These noise contour maps have shown noise levels in the eastern parts of Foster City area of maximum of 66 decibels when jets are landing at SFO [City of Foster City, 1981]. One criteria for measurement of noise is called CNEL, or Community Noise Equivalent Level, which is expressed in decibels, and puts greater emphasis on noise at night. The CNEL is an average A-weighted noise level during the 24-hour day, with the addition of 5 db from 7 pm to 10 pm and the addition of 10 db from 10 pm to 7 am [City of Foster City, Final EIR,4/93, pg.184]. The Environmental Protection Agency (EPA) has set the noise level of a maximum of 55 decibels for protection of human health.
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