A new boundary-element method for predicting outdoor sound propagation and application to the case of a sound barrier in the presence of downward refraction

Abstract

A new boundary-element method for predicting outdoor sound propagation over uneven ground is presented. This allows the sound field around complex boundaries (various absorptive properties and shapes) and in the presence of refraction to be calculated accurately. The total sound pressure is expressed as the sum of the incident pressure and the pressure scattered by the obstacles in the propagation medium, involving layer potentials. The Green’s function used in this formulation takes meteorological and ground effects into account and relies on recent models for propagation in inhomogeneous media, such as normal modes, residue series, the parabolic equation, or the fast-field program. In this paper, this new method, called Meteo-BEM, is derived, based on both boundary-element methods (BEM) in a quiescent medium, and propagation models in inhomogeneous media. The hypothetical case of a rigid, thin noise barrier on a flat ground, under a known sound-speed gradient condition, is studied. Comparison of numerical simulations with experimental results shows that this new method is a powerful tool for outdoor sound propagation prediction, which gives rise to many applications and developments.