Studies on Community Noise in a Japanese Inland Middle-sized City

Abstract

The sound-proof walls established in two elementary schools of T City were surveied for their soul-insulating effect. Also noise propagation was investigated along the superexpress railways Shinkansen and an automobile express way to seek its effect on the regional environment. The results were as follows : 1) The measured values of some points of traffic noise were compared with the values on the noise decrement curve against distance, which was theoretically obtained by taking, as the sound level of source, the measurement at a point close to the traffic sound source, on the assumption that the traffic noise has a linear sound source. The measurements in the two schools only partly approximated the theoretically obtained values on the decrement curve, but were closely similar to the measured values alongside the Shinkansen and automobile express way. 2) The sound-insulating effects of the sound-proof walls in the two elementary schools were estimated by comparison with the noise measurement at a control site. The walls were found to diminish the railroad noise only by 5-10 dB, and in the school house with windows opened, the noise level was 66 dB at the min., and 84 dB at the Max.. Some kinds of train fairly impulsively emitted noise, which lasted about 30 seconds during the passing of the train. This occurred at about 12 min. intervals on the average, and was consequently assumed to affect learning efficiency. In a school beside a traffic road, which is a cutting road, the sound-proof wall up on the mural side of the road was appreciably effective in arresting sound. 3) The prospective effects of noises of the Shinkansen and automobile express way on the regional environment of T city were estimated from the results of survey on the vicinity of the existing ones. Noise in the residential quarters on both sides of the Shinkansen within the range of 300m from the railroad (exclusive of bustling streets near the station) was estimated at about 70 dB. On both sides of the automobile express way within 100m from it, the noise is estimated to fluctuate by about 10 dB, and within 400m, noise of about 50 dB will be constantly present with a slight variation.