Abstract
The temporary threshold shift (TTS) produced by intermittent noise of duty cycle less than 4 minutes was examined on five subjects with normal hearing acuity. The net duration of exposure was fixed as long as thirty minutes and the on fraction (R) and duty cycle (D) of intermittent noise were varied as follows. R: 0.2, 0.4, 0.5, 0.6, 0.8 D: 1, 4, 16, 60, 120, 240 sec. TTS at 2, 3, 4, 6, and 8 kc following each exposure of total thirty combination of R and D were compared with TTS produced by continuous exposure. Results obatained were as follows. 1. TTS at any test frequency (form 2 kc to 8 kc) was approximately proportional to the on fraction (when duty cycle was in the range from 1 second to 4 minutes). 2. Although TTS produced by noise of which duty cycle was 2 minutes or 4 minutes seemed to be smaller than those by shorter duty cycles, no signicant differences were recognized in the analysis of variance among duty cycles.
