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Source: B.G. Liptak, ed, 1974, Environmental engineers' handbook, Vol. 3 (Radnor, Penna.: Chilton Book Company).

aIf ear protectors are not worn, even the shortest exposure is considered hazardous at levels above 135 dBA. If ear protectors are worn, no exposure to levels above 150 dB, however short, is considered safe. These criteria assume that hearing loss will be within acceptable limits if, after 10 years, it is no greater than 10 dB below 1000 Hz, 15 dB up to 2000 Hz, or 20 dB up to 3000 Hz.

Source: B.G. Liptak, ed, 1974, Environmental engineers' handbook, Vol. 3 (Radnor, Penna.: Chilton Book Company).

aIf ear protectors are not worn, even the shortest exposure is considered hazardous at levels above 135 dBA. If ear protectors are worn, no exposure to levels above 150 dB, however short, is considered safe. These criteria assume that hearing loss will be within acceptable limits if, after 10 years, it is no greater than 10 dB below 1000 Hz, 15 dB up to 2000 Hz, or 20 dB up to 3000 Hz.

levels of noise. The EPA guidelines were developed to protect public health and welfare (U.S. EPA 1974). These guidelines are summarized in Table 4.4.3.

The Department of Housing and Urban Development (HUD) has established guidelines for noise levels in residential areas. They define categories of acceptability as follows: acceptable if the Ldn is less than 65 dBA, normally unacceptable if the Ldn is greater than 65 dBA but less than 75 dBA, and unacceptable if the Ldn is greater than 75 dBA (HUD 1979). According to EPA studies, the majority of complaints occur when the Ldn exceeds 65 dBA (U.S. EPA 1973).

When land uses are noise sensitive, as with hospitals, parks, outdoor recreation areas, music shells, nursing homes, concert halls, schools, libraries, and churches, more restrictive guidelines are used. Conversely, less restrictive guidelines are used for commercial and agricultural land uses. For example, Table 4.4.4 shows a set of U.S. Navy noise guidelines for various land uses.

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