Evaluation of proposed limits for intermittent noise exposures with temporary threshold shift as a criterion.
Schmidek-M; Henderson-T; Margolis-B
Safety standards for noise exposure in underground surface coal mine operations, developed by a working group of the National Academy of Sciences - National Research Council Committee on Hearing, Bioacoustics, and Biomechanics (CHABA), are found to be deficient in three ways. Mean temporary threshold shift (TTS) data, measured at 2 minutes after exposure (TTS-2) to select noise conditions providing the maximum exposure limits under the CHABA damage/risk criteria, suggest that the mean TTS-2 values for frequencies 2000 Hertz and above are not equal to nor in compliance with the CHABA standards. Concentrations of noise exposure are permitted in an 8- hour workday which can cause excessive amounts of TTS, posing risk of permanent hearing loss. The maximum permissible conditions of exposure do not yield equal effects on hearing and may not afford equal protection. Investigation of sound levels during breaks between periods of high level noise exposure reveals that the definition of interruption may need further clarification as to sound levels required to foster maximum aural recovery from the intense noise segments of an intermittent noise condition.
Noise-control; Hearing-loss; Protective-measures; NIOSH-Author; Sound-levels; Acoustic-environment; Mining-industry
National Noise Study, Division of Epidemiology and Special Services, National Institute for Occupational Safety and Health, Public Health Service, U.S. Department of Health, Education, and Welfare, Cincinnati, Ohio, 14 pages