Environmental noise is defined as "the noise emitted from all sources except in the industrial workplace" (Schomer and Associates, 2001, p. 1). Major sources of environmental noise come from road, rail and air traffic. In the United States, over 40 percent of the population is exposed to transport noise exceeding levels of 55 decibels (Schomer and Associates, 2001, p. 1). The decibel is a way to measure noise. The decibel allows people to understand sound strength using numbers ranging between 20 and 120 (Richards, 1973). Noise pollution continues to grow, especially in complaints in the area of air traffic. .
Annoyance is the most prevalent effect of aircraft noise. It is important that while the average noise level in the community is usually what is reported, some people will be more upset or annoyed with the sound. The effects of noise pollution of air traffic do not cause dramatic injuries, but they do affect physical areas of the body. Sleep disruption, masking of the television and conversations, and chronic stress, or even hearing damage (World Health Organization, 1999).
There are agencies that are currently dealing with noise issues. The Federal Aviation Administration (FAA) uses the (Average Day Night Sound Level) (DNL) metric for measuring noise in environmental assessments and so-called "Airport Part 150 Studies". These are studies that are done in the vicinity of airports. The FAA recommends a minimum of 65 DNL to impact residential areas (FAA, 2000). .
The Department of Defense (DOD) uses the DNL for "Air-Installation Compatible Use Zone Studies". These are studies for use noise impact in the vicinity of air installations. The DOD recommends a minimum of 65 DNL to impact residential areas (DOD, 1977).
Nearly all agencies and boards, people who set standards over noise producing sources use a DNL of 55 decibels as the threshold for noise impact in residential areas. The only agencies that are above the 55 decibel level are the Department of Defense and the Federal Aviation Administration (Schomer and Associates, 2001).