Efficient edge source approach to the modeling of multi-edge noise barrier tops

The scattering from rigid polyhedra can be efficiently and accurately modelled with an edge source integral equation. The modeling is based on a separation of the sound field into three terms: a geometrical-acoustics term, a term which represents first-order diffraction, and a term which represents second- and higher-order diffraction. It is the latter term which is expressed through an integral equation whereas the first two terms are available explicitly. One set of noise barrier designs, infinite barriers with parallel-edge top designs, can furthermore be modelled with a particularly efficient form of that integral equation which exploits the symmetry property of the parallel edges and plane wave incidence. The symmetry formulation will be demonstrated in this paper, together with numerical examples and a discussion of implementation issues. Special numerical issues are related to singularities in certain scattering directions, and to the computation of the oscillating integrals that result. The underlying integral equation is valid for convex scatterer geometries, and the issues with non-convex geometries will furthermore be discussed together with examples such as Y-shaped noise barrier top designs.