Low‐frequency long‐range sound propagation over impedance discontinuities with the parabolic approximation

Abstract

Previous studies have shown that the parabolic approximation method, widely used in ocean acoustics, can be successfully applied to low‐frequency long‐range atmospheric sound propagation over a locally reacting boundary, an important problem with many applications. This work models cw acoustic signals as they propagate over horizontal ground surfaces with impedance discontinuities. An implicit finite‐difference implementation of the parabolic approximation sound propagation model incorporating locally reacting, variable‐impedance ground surfaces is employed to compute estimates of the sound field excess attentuation for a variety of flow resistivities and source frequencies. Both windy and stationary atmospheres are considered. An accuracy benchmark and several example problems in which the sound propagation path includes an idealized lake will be discussed. [Work supported by NASA.]