Multiple reflection of traffic noise in the city area

Abstract

In Tokyo, it is very difficult to get the space for road construction. Twelve-million people are concentrated in a limited area. Many houses and buildings are arranged closely on both sides of the street, and city freeways are built frequently above the main street by overhead elevated constuction. In such cases the noise radiated from vehicles is reflected between houses, buildings, the bottom of the elevated road, and the lower street surface, and consequently the sound level observed along the street is higher than that in the case of open area. The effect of the buildup of sound level caused by multiple reflection in city area was studied by means of 1/40 scale model experiments and field measurements. Scale model experiments were carried out concerning various conditions of reflection by using an incoherent line source, and spacial distribution of SPL surrounding the road and the street was observed. Results of the scale model experiments showed similar tendency to that of field measurements. Relations between the buildup of SPL and various factors of sound reflection, for instance, the width of street, the height of buildings, houses, and elevated road and so on, were discussed. The results of this study will be applicable in the road traffic noise prediction at the point located in the roadside.