Effects of high-sided vehicles on the performance of noise barriers

Abstract

The attenuation produced by a given barrier can be maximized by placing it as close to the noise source or receiver as possible. This fact and the availability of land often means that barriers are situated close to the edge of the road. In this position the performance of the barrier can be degraded by the effects of multiple reflections of sound between the sides of the vehicles and the barrier. This paper reports the results of calculations, carried out using a two-dimensional boundary element model, of the attenuation produced by various configurations of barrier adjacent to a traffic stream. Spectra of insertion loss and the mean broadband insertion loss in the shadow region are considered. The effects of the height of the vehicle, the distribution of absorbing material on the traffic-facing side of the barrier, and the slope of this face are considered quantitatively in terms of the peak noise level. It is concluded that serious degradation of the performance of the barrier can occur for some situations, especially when the side of the vehicle protrudes above the barrier. The results indicate the extent to which the problem can be overcome by the use of absorbing barriers or by sloping barriers of suitable design.