Technical Assessment of the effectiveness of noise walls

The principal objective of this study is to obtain a global view of the effectiveness of noise walls-the outdoor barriers erected in parallel with highway and rail lines, and in other areas (such as airport runways). The report summarizes the scientific basis of noise barriers, including measures of barrier efficiency, the physical phenomena involved (including effects associated with the propagation and effects associated with the noise wall as well as different barrier shapes), and the various models used to predict barrier performance, Different barrier materials are briefly described. The measurement of barrier effectiveness is also discussed. A section discusses the three main application areas where barriers are used: road traffic noise, railroad noise, and ground-based aircraft operations. Finally, the main conclusions are presented along with recommended directions for future research.