Study of Sound propagation over range-dependent and topographic ground by finite difference model

This paper extends an earlier study on sound propagation over layered ground to range-dependent and topographic ground. The model is based on a pressure-velocity finite-difference formulation and is coded in the computer program PORAC. To highlight theinfluence of range-dependent parameters and topographic features on sound propagation, four cases are considered: (i) a homogeneous poro-elastic half-space (the base case); (ii) the base case with a zone in the ground with a higher permeability; (iii) the base case with a zone of higher stiffness and (iv) the base case with a rectangular hill. The paper presents typical results of sound propagation in these cases comprising synthetic time histories of overpressure in the atmosphere and ground vibration as well as snap-shots of the response of the atmosphere-ground system at selected times. Comparative results in these cases serve to highlight the effect of the various non-homogeneities considered in this study.