Temporary threshold shift to 8-h noise exposures in man and monkey

Abstract

Few investigators have studied the appropriateness of an animal model for the effects of noise on hearing in the human. The goal of our research is to provide such data for the squirrel monkey. Our approach was to reproduce industrial working conditions by using exposures of work-day length and recorded factory noises, in addition to octave-band and pink noises for both humans and monkeys. The results enable us to compare the effects of commonly used laboratory noises with those of recorded factory noises on man and monkey. We exposed 20 humans and 12 squirrel monkeys twice to each of five different noises (pink noise, two octave bands centered at 500 Hz and 4 kHz, stamping plant noise, and stall wrench noise) for 8 h at each of two levels. Auditory thresholds were determined after 1, 2, 4, and 8 h of noise exposure. TTS growth to each noise demonstrates that the squirrel monkey is similar to the human in the manner in which auditory thresholds shift as a function of time for these various noises. Presumably, the physiological changes underlying TTS are also similar for the two species. [Work supported by NIOSH.]