Simulation of noise barrier insertion loss using the boundary element method

Abstract

Within a project of the European Commission "Calm Tracks & Routes" the performances of different styles of noise barriers were investigated. Additionally new methods for increasing the absorption were investigated. A central theme was to investigate the mitigation of curved walls with high absorption coefficients, because studies made before the project gave the hint that noise barriers curved away from the source should give satisfying insertion loss. Due to the curvature the view in the landscape is hindered to a lesser degree compared to straight noise barriers. The investigation of the noise barriers was done by boundary element methods. An absorptive model for grassland was added and implemented into Green's functions. Due to the existence of smeared sources the application of the fast multipole method was not possible and the simulations were limited to the two-dimensional case. It became obvious that the distance of the source is important for the mitigation of curved noise barriers with respect to straight ones. Therefore different wall types and source positions were investigated. The results of the numerical simulation were compared to measurements in situ and in a large anechoic chamber.