Abstract
Audiometrically normal, male students were exposed to Impact Noises by tapping machines (B duration, ca. 300msec) for 40 minutes and the following results were obtained.
1) Sound level of Impact Noises (10pulses/sec) were measured using a sound level meter which was set at the “slow”. It was 95dB. (all pass)
TTS growth (Test Frequency 4kHz) due to Impact Noises were not significantly greater than due to steady-state Noises. (95dB (all pass))
2) In the exposure to Impact Noise (1pulse/4sec), TTS growths of 125dB at the peak values were significantly greater than that of 120dB at the peak values at the both 1kHz and 4kHz.
From these results it is permissable to measure the sound level of impact noise (10pulses/sec, or more pulses per second) for the evaluation of harmfulness using the sound level meter. The data obtained by our experiment concerning TTS growth at 4kHz supports the criterion proposed by Coles.
