Occupational hearing conservation.

Chronic exposure to high-intensity noise can produce permanent hearing loss, the amount of which depends on noise intensity, temporal and spectral characteristics, and the length of exposure. OSHA regulates workplace noise exposure in accordance with the Hearing Conservation Amendment of 1983. When noise levels equal or exceed an 85 dBA time-weighted average (TWA), the employer is required to provide annual audiometric screening. When noise levels exceed 90 dBA TWA, the worker's exposure must be reduced by engineering methods, administrative changes, or personal hearing protectors. If a worker demonstrates a standard (significant) threshold shift (10 dB or greater increased average hearing threshold at 2, 3, and 4 kHz in either ear) that is attributed to noise, the worker's exposure must be further reduced by one of the aforementioned methods.