Noise propagation from a cutting of arbitrary cross-section and impedance

A boundary integral equation is described for the prediction of acoustic pr opagation from a monofrequency coherent line source in a cutting with imped ance boundary conditions onto surrounding flat impedance ground. The proble m is stated as a boundary value problem for the Helmholtz equation and is s ubsequently reformulated as a system of boundary integral equations via Gre en's theorem. It is shown that the integral equation formulation has a uniq ue solution at all wavenumbers. The numerical solution of the coupled bound ary integral equations by a simple boundary element method is then describe d. The convergence of the numerical scheme is demonstrated experimentally. Predictions of A-weighted excess attenuation for a traffic noise spectrum a re made illustrating the effects of varying the depth of the cutting and th e absorbency of the surrounding ground surface. (C) 1999 Academic Press.