Squirrel monkey temporary threshold shift from 48-h exposures to low-frequency noise.
Five squirrel monkeys were exposed for 1, 2, 4, 8, 16, 24, and 48 h to a 375--750-Hz band noise at an overall SPL of 95 dB. The TTS4.5 growth pattern for the 750-Hz test frequency was biphasic and did not reach an asymptote after 48 h of exposure. For all exposures, the mean thresholds of the five monkeys returned to within 5 dB of the preexposure mean 20 h after exposure. Recovery curves from all exposures at the 750-Hz test frequency appeared biphasic. Increasing SPL from 95 to 105 dB increased TTS4.5 by 4 dB at 750 Hz for a 1-h exposure. Recovery from the  105-dB exposure followed the same pattern as recovery from the 95-DB exposure. When compared with data collected from human subjects under similar conditions, these experiments indicate that the growth and recovery of TTS in squirrel monkeys are sufficiently similar to growth and recovery in man to justify further comparative investigation.
D000818:Animals; D001309:Auditory Threshold; D000882:Haplorhini / Q000502:physiology*; D006801:Humans; D008297:Male; D008722:Methods; D009622:Noise / Q000009:adverse effects*; D012453:Saimiri / Q000502:physiology*; D013997:Time Factors