The relationship of the exchange rate to noise-induced hearing loss.
NIOSH 1992 Sep; :1-58
The use of the exchange rate concept for predicting noise induced hearing loss based on noise level and duration was reviewed and discussed. The selection of an appropriate exchange rate necessitates examining the growth of equal hearing hazard as a function of noise level and duration. This relationship depends on numerous variables, including the measure of damage, the audiometric frequencies to be protected, and various temporal and acoustic parameters such as the noise on time and off time and the level of quiet during interruptions. Several assumptions and methods for predicting permanent hearing damage were discussed. Evidence from several animal studies and certain field studies suggested the 3 decibel (dB) exchange rate, but to allow an adjustment to the maximum permissible exposure limit for outdoor, intermittent noise exposures. This was in contrast to a 5dB exchange rate, for which there appeared to be little scientific support. The amount of such an adjustment should ideally be determined by the temporal pattern of the noise and the levels of quiet between noise bursts. The author suggests that until further information becomes available, the adoption of a conservative approach would be to allow a small increase, such as 2dB to the permissible exposure limit for outdoor occupations.
NIOSH-Contract; Noise-induced-hearing-loss; Hearing-loss; Noise-exposure; Ear-disorders; Hearing-threshold; Steady-state-noise
Final Contract Report
NTIS Accession No.
Division of Standards Development and Technology Transfer, NIOSH, U.S. Department of Health and Human Services, NIOSH Purchase Order Report 9139562, 58 pages, 100 references