THE EFFECT OF BUILDING DENSITY AND SIZE ON THE PROPAGATION OF SOUND THROUGH THE URBAN FABRIC

The net effect at a location deep in the urban fabric of noise arising from the operation of multiple distant sources can be expected to be a function of the building density and typical size of buildings in this area. However, little is known as to how these characteristics of the urban fabric affect noise propagation. In this paper sound propagation through a distributed array of medium sized simple building forms has been investigated, assuming that building faces p roduce perfect diffusion. The method adopted was to calculate the energy exchange between facades assuming hemispherical propagation from a point located at the centre of the illuminated area of a facade. Thus, the energy exchange between faces is replaced by arrays of point sources located o n each face For the very regular street configuration employed in the model, it was found that there was a strong channeling effect when the source was located between facades lining a street. The propagation of sound across a more irregular fabric configuration as a function of building density, building ground floor dimensions and building height was investigated. It was found that the sound attenuation rates for each configuration are linear and virtually identical. However, for each configuration there are differences in levels at a particular location that can be attributed to the near field effect of local occlusion in the vicinity of the source. The similar attenuation rates suggest that after the initial occlusion effect has determined the amount of sound energy that progresses to the far field, the effect of occlusion for a higher building density is compensated for by reflections from the facades.