自動車交通騒音の大きさについて

抄録

With the spread of transportation systems on the road, the effects of traffic noise have become one of the most serious problems in our daily life and some epoch-making counter-measure has earnestly been waited for. We have to measure the traffic noise first in order to control it. Present experiments were designed to investigate what kind of estimated value of traffic noise is most suitable to predict the loudness of traffic noise. All the stimuli used in these experiments were the traffic noises recorded on magnetic tape. In Exp. I the loudness of 5sec traffic noise, generated when only one vehicle passed was obtained, using the method of subjects' adjustment. That is, subjects were asked to match the loudness of pink noise with that of traffic noise by controlling the level of pink noise using a remote control attenuator. The results show quite good correlation between loudness and any one of estimated values of traffic noise (dB(A), SIL, NRN, LL, PNL, L_&lteq&gt). So long as the traffic noise generated by one vehicle is concerned, any estimated value seems to be suitable. Among them L_&lteq&gt appears to be better since its standard error is small. In Exp. II the loudness of 1min traffic noise, during which various kinds of vehicles passed, was obtained. As in Exp. I the method of subjects' adjustment was adopted. From this experiment all the estimated values, except maximum level, TNI and L_&ltnp&gt, were found to have high correlation with loudness. Among them L_&lteq&gt had the smallest standard error. In Exp. III the impression of traffic noise used in Exp. I and II was measured using the semantic differential method. Subjects were asked to estimate the traffic noise using 13 scales of adjectives. As a result of factor analysis, three factors were extracted: powerful, pleasant, and metallic. Coefficients of correlation between estimated values of traffic noise and factor scores show that the upper values of traffic noise such as L_&lteq&gt or L_5 have a high correlation with the "powerful" factor. From these experiments it might be concluded that L_&lteq&gt is the most effective value as a representative of traffic noise since it is highly correlated with subjective estimation of traffic noise and for practical purposes it can be easily calculated. Our previous experiments concerning the loudness of level-fluctuating noise ascertain this fact. Further, it is said recently that it is the upper value of traffic noise that corresponds well with the annoyance of residents.