変動騒音によるTTSの研究

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In order to investigate the temporary threshold shift (TTS) produced by fluctuating noises, two experiments were carried out changing the levels of white noise every five seconds in accordance with the previously arranged programs. In the first experiment eight kinds of noises having the following properties were selected and classified into two groups (A,B) according to the shape of correlogram. 1) Fluctuating levels follow the normal distribution with the mean, 95 dB, and the standard deviation, 3.60 dB. 2) The number of level-changing is 240. Consequently, whole exposure time becomes 20 minutes. (240×5 sec) 3) Correlogram for each noise is expressed as follows: noises of Group A a) ρ_k=1 for k=0 =0 for k>0 b) ρ_k=-1/(10)k+1 c)ρ_k=0.7^k d) ρ_k=0.775^k[cos k(58°54′) +0.151 sin k(58°54′】 where ρ_k is autocorrelation coefficient and k is integer. noises of Group B e) ρ_k=1 for k=0 f) ρ_k=-1/(20)k+1 g) ρ_k=0.8^k h)ρ_k=0.775^k[cos k(32°58′) +0.400 sin k(32°58′)] Seven subjects were exposed to noises of Group A and other five subjects to noises of Group B. They were also exposed for 20 minutes to steady-state white noise at 95 dB. TTS at 3,4,6 and 8 kHz were measured. Using the analysis of variance technique, TTS date for Group A and for Group B were respectively analyzed. There were no significant differences (level of significance: 0.05) in TTS between the exposure noises. In the second experiment the levels of exposure noises were changed alternately between S_1 dB and S_2 dB, holding the value of (S_1+S_2)/2 constant (100dB). The values of S_1 and S_2 were selected as follows: [table] (S_1-S_2=0 means that the noise is a steady-state noise at 100dB). TTS at 2,3,4,6 and 8 kHz produced by ten minutes' exposure to these noises were found to be approximately the same regardless of the temporal characteristics of the exposure noises.
社団法人日本産業衛生学会の論文
1969-08-20

変動騒音によるTTSの研究

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