Barrier designs to reduce road traffic noise

Abstract

Traffic noise reduction is an important area of public concern since nearly ten per cent of the population are seriously bothered by this type of noise. The reduction of noise annoyance can be tackled at any stage from generation at the source to the perception by the listener. Three stages can be identified: generation, propagation and reception. Mitigation measures fall into all three categories and an overview of relevant research into reducing sound propagation using roadside barriers is described in this paper. It should be borne in mind that to obtain a significant reduction in noise it may sometimes be necessary to effect a reduction at two or more stages. This is a ‘combined mitigation’ approach; for example, the use of low noise surfaces with noise barriers. Cost-effectiveness is also very important especially when public funds are involved. Additionally, public acceptability needs to be considered since a mitigation may be highly effective in reducing noise but not appropriate; for example, a visually intrusive noise barrier. Underpinning the research carried out by TRL have been significant advances in mathematical modelling that have allowed complex situations to be modelled accurately. This has involved the use of Boundary Element Methods (BEM) and a key requirement has been the need to validate the results as the method has developed. A noise barrier test facility at TRL has allowed a wide variety of barrier shapes to be tested at full scale to measure values for comparison with model predictions. Agreement has been good which has given confidence in the modelling approach adopted.