Damage-risk contours for intermittent noise exposures.
NIOSH 1977 Aug; :1-21
NIOSH-sponsored research was conducted on the development of contours that would specify equal risk for intermittent noise exposures. A total of about 300 different exposures to steady and intermittent broad, narrow, and octave band noises were given to 10 young normal listeners. A complete preexposure audiogram at half octave intervals was administered to each subject before the exposure and 16 hours after its termination. Results indicate that: 1) exposures need not be quite 8 hours long to give valid results; 2) for octaves except 2000 and 4000Hz, reducing exposure by means of intermittency cuts the amount of temporary threshold shift (TTS) down so drastically that even the 5dB exposure rule is over conservative; 3) effective quiet levels were about 76dB for octave bands at and below 500Hz, and around 68dB at 1000Hz and above; 4) contours defining SPLs that produced 10 or 20dB of TTS2 after an 8 hour exposure were not as flat as the 0dB TTS2 contour; 5) not all hazardous real life noises have a constant spectrum, although most do; 6) even in the exposure with the greatest disparity among levels, the TTSs at 500 and 1400Hz were identical to those produced by steady 90dBA noise; 7) burst duration varies in actual work situations; 8) intermittency of noise reduces noise hazards; 9) alcohol appears to pose no synergistic threat to the hearing of workers in noisy industries; and 10) testing produced no significant alterations in the subjects' hearing.
NIOSH-Grant; Hearing-tests; Environmental-control; Exposure-limits; Long-term-exposure; Noise-control; Sensory-perceptual-processes
Otolaryngology U of Minnesota Box 461 Mayo Minneapolis, Minn 55455
Final Grant Report
Department of Otolaryngology, University of Minnesota, Minneapolis, Minnesota, Terminal Progress Report, NIOSH Grant No. R01-OH-00350, 21 pages, 10 references
University of Minnesota Minneapolis, Minneapolis, Minnesota