Influence of impedance distribution and optimal impedance design in the context of noise barriers.

Abstract

Noise barriers are commonly used to protect people from railways or roads traffic noise. However, the optimal design of those barriers is still an open problem since lots of different results have been obtained, depending on the method utilized. In this paper, instead of focusing on the shape of the barrier itself, a new method involving optimization of the impedance distribution on a control surface of simple geometry and containing the barrier has been used. First, numerical simulations have been carried out with the two dimensional boundary element method in order to predict the sound pressure level around any impedance scatterer. Analytical solution for the scattering of a line source by an infinite constant impedance circular cylinder has been derived and used for validation. Second the influence of the impedance distribution in the case of a circular cylindrical control surface has also been studied to determine an optimal impedance distribution to control the noise level in a zone close to the barrier. Specific attention has been paid to the scattering of multiple line sources in order to model high‐speed train noise sources more accurately.