Sound propagation over noise barriers with absorbing ground

The main purpose of this article is to present a numerical method for calculating the sound pressure around noise barriers of arbitrary geometry. Varying impedance boundary conditions on the barrier and constant impedance on the ground are assumed. Sound propagation over an infinite barrier with a constant cross-section for an harmonic point source is determined by solving 2D problems only, avoiding the computational complexity of the solution of a true 3D problem. This can be done by using the solutions of a set of 2D models for a coherent line source for real and imaginary wavenumbers. This extension to calculations for imaginary wavenumbers is the main feature of the proposed method. A Fourier transform of the 2D solutions allows a calculation of the 3D solution for a point source. The 2D numerical solutions are obtained by a classical use of the Boundary Element Method. Moreover, the 2D Green function for imaginary wavenumbers in the case of a half-space bounded by a surface of uniform impedance is developed. Finally, examples are given to estimate the accuracy of the method and some practical cases of calculations around barriers are presented and compared with experimental data.