Human Temporary Threshold Shift From 16-Hour Noise Exposures

Existence of an asymptotic development of change in threshold hearing sensitivity from long noise exposures has important implications for estimating the hazards of environmental and industrial noise. The present study investigated temporary threshold shift (TTS) resulting from 16 hours of continuous exposure to an octave band of noise, 300 to 600 Hz, at octave band levels of 80, 85, 90, and 95 dB. Ten subjects were tested at each level. Thresholds were measured at frequencies ranging from 125 to 8,000 Hz during and after the noise exposure. Group data indicate that the 16-hour exposure period was not long enough to clearly establish asymptotic levels of TTS. As a group, these subjects recovered to within 5 dB of preexposure threshold measures by 58 hours postexposure. Individual subject variability was notable in the pattern of TTS development.