Effective quiet and moderate TTS: implications for noise exposure standards.
Ward WD; Cushing EM; Burns EM
J Acoust Soc Am 1976 Jan; 59(1):160-165
Effective quiet, the highest sound pressure level of a noise that will neither produce a significant temporary threshold shift; or TTS, nor retard recovery from a TTS produced by a prior exposure to a higher level, is shown to be about 76 decibels for octave bands of noise centered at 250 and 500 hertz and around 68 decibels for those centered at 1000, 2000, or 4000 hertz. On the other hand, a mean TTS 2 minutes after exposure of no greater than 10 decibels at all frequencies from 500 to 5600 hertz is produced by a broad-band noise whose octave-band spectrum falls off at - 5 decibels per octave ("magenta" noise) and which has an A-weighted level of 90 decibels. When the group mean TTS is 10 decibels, less than 10 percent of normal ears will show a TTS of 20 decibels. Therefore if a 20 decibels TTS is tolerable day after day with no adverse effects, the present industrial noise exposure limit of 8 hours at 90 decibels A would adequately protect more than 90 percent of exposed workers in noise with similarly falling spectra. Correction factors for unusual spectra should, however, be developed.
NIOSH-Publication; NIOSH-Grant; Noise-induced-hearing-loss; Noise-levels; Noise-control; Acoustical-measurements; Hearing-threshold; Safety-measures; Ear-protection; Occupational-health; Control-measures; Safety-standards
Otolaryngology U of Minnesota Box 461 Mayo Minneapolis, Minn 55455
Journal of the Acoustical Society of America
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