知的作業時の精神疲労に及ぼす航空機騒音の影響 : 防音室内曝露実験

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Studies of mental fatigue caused by exposure to the aircraft noise was carried out experimentally on 9 female students engaged in some intellectual performance. The tape-recorded noise of the flying Jet engine was controlled from 85dB(A) to 95dB(A) in the peak level. The subjects were exposed continuously to the noise during 50 minutes and 100 minutes, respectively, in an insulated room protected from general outer noise.<BR>Through the noise exposure period, the subjects performed intellectual tasks, that is, the Kraepelin- Uchidas test and card-sorting test. At the same time, pulse rates and pulse waves of their fingertips were measured. Before and after each exposure, the mental fatigue was measured by the critical fusion frequency (C.F.F.), the color naming test (C.N.) and the discriminative reaction of the multiple performance test (M.P.). And the information of subjective sensations of human fatigue were collected by the questionnaire, Cornal Medical Index (C.M.I.) were used for psychophysiological complaints. The control data of each subject were obtained by the same experiment except noise.<BR>The following conculusions were derived from observations. The grade of mental fatigue increased in the case of the noise exposure rather than in the case of the noiseless situation. In C.F.F., fatigue increased 13% under noise exposure of 50 minutes, 37% under that of 100 minutes. In C.N. and M.P. as wel as C.F.F. the same gradiance between the noise exposure and fatigue were found. Furthermore, fatigue revealed itself more clearly in C.N. than in C.F.F., namely, the rate of prolongation of the time required for color identifying exceeded the critical level of mental fatigue, while the rate of mental fatigue in C.F.F. was within the normal or allowable range.<BR>The results of the questionnaire of subjective sensations of fatigue and of the C.M.I. in the case of the noise exposure showed no remarkable differences compared with those of the noiseless situation. But, it was found that some complaints of sensations of fatigue increased slightly during noise exposure compared with those in the noiseless situation. These complaints were the symptoms probably caused by the sympagotonic hypertension. Moreover, from the observation of the pulse rates and pulse waves, it was recognized that a biological lags of the relaxation of the sympathetic nerves system might occur when they were released from the intellectual tasks.<BR>From the observation mentioned above, it is considered that there is a posibility of the inhibition of the learning effectiveness in school children when they are exposed to the aircraft noise such as the subjects were exposed to in this experiment. The exposed aircraft noise level used in this study, calculated from the peak levels and flying numbers, corresponds to 80 W.E.C.P.N.L.. It can be said that mental fatigue is induced markedly by the noise of 80 W.E.C.P.N.L.. It is suggested that the noise level of 80 W.E.C.P.N.L. is not harmless to human being in the case of intellectual performance, especially during school hours.
日本衛生学会の論文

知的作業時の精神疲労に及ぼす航空機騒音の影響 : 防音室内曝露実験

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