Agenda - 11-22-2004-c1 - Laserfiche WebLink

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23 Environmental Sound Page 8 /attachment 3 Effects of Noise The scientific community has documented many effects ofnoise on people and their activities. Some are directly related to the noise. Others aze related indvectly as a result of stress induced by the noise. The United States EPA has recognized clear evidence that noise of sufficient intensity and duration can Temporarily or permanently damage hearing, Affect performance of a complicated task, Interfere with speech and other auditory communication, Disturb sleep, and Be a source of annoyance, These effects could be expected to affectthe value ofnoise-impacted property. Studies based on aircraft noise have indicated a value reduction of .5 to 2.5% per decibel increase in average sound level for residential properties.. The level and duration ofnoise required for hearing damage is greater thanthatrequired for other effects.. Hearing loss is razely an issue m residentialareas. Hearing losses typically occur from work or recreational exposure to loud sounds. Heazing loss is an issue for participants and workers at the firing range. High sound levels cause a person at work to concentrate their attenfion to their most important task. This improves performance on simple tasks, but deteriorates it in more complicated cases where several tasks aze done at once. Most of the research in this area has been done for sound levels over 70 dBA which occur infrequently in residential areas. Communications interference, sleep interference, and general annoyance effects azewell documented noise problems in communities, These effects, especially annoyance, occur for a wide range of sounds varying in level, frequency and temporalchazacteristics. Non-acoustical factors also strongly influence annoyance. Stress induced by annoyance can affect the ability ofthe body to fight exisfing ailments. Annoyance, and interferences with communication and sleep are discussed in more detail below. Communications Interference Most people at one time or another have experienced communication difficulty as a result of background noise levels. The degree of interference depends on many factors. These include the level and steadiness of the interfering noise, (particularly the level of the noise at speech frequencies), the listener's prior knowledge or anticipation of part ofthe transmitted information, and the sound level of the transmitted information. The sound level of the transmitted information at the listener depends on the distance between the source and the listener. For a speaker and listener outdoors, around 6 feet apart, the beginning of speech interference by many common steady noises is at around 60 dBA.