Abstract
Ten young students with normal hearing acuity were exposed to white noise band-pass-filtered from 0. 9kHz to 9kHz for 24 hours in a reverberant room. Sound pressure levels of the exposure noise were 65, 70, 75, 80, 83 and 86dB. Thresholds of hearing at 2, 3, 4, 6 and 8kHz were measured before exposure, at some given time during the course of the exposure and after the exposure. Thresholds were also measured without noise exposure for 24 hours in the same way as was done with exposure to noise. The results showed that no significant threshold shift was observed when the subjects were not exposed to noise and that significant threshold shift was observed at all the levels of exposure noise when they were exposed to noise. Time after onset at which the temporary threshould shift (TTS) reached an asymptotic level ranged from 1. 6h to 46h. The asymptotic levels at 3, 4, 6 and 8kHz of the test frequencies were 4. 4, 3. 7, 8. 2 and 4. 2dB, respectively, when the exposure level was 65 dB and 14. 3, 21. 6, 21. 8 and 17. 6dB when it was 86dB. Linear relation between the asymptotic threshould shift and the exposure level was found and the slopes of the line were 0. 55, 1. 1, 1. 0 and 0. 81dB/dB for the test frequencies of 3, 4, 6 and 8kHz.
