A parabolic equation method for predicting sound propagation above and below a layered ground

Abstract

A numerical model based on a wide-angle parabolic equation (PE) technique has been developed for calculating the sound fields above and below a layered ground. A finite element discretization was applied along the vertical direction instead of the classical finite difference scheme. By using the finite element approach, the boundary conditions, i.e., the continuity of pressure and velocity, can be incorporated directly at the air/ground and ground/ground interfaces. The range-dependent sound fields were obtained by marching the finite-element solutions (above and below the layered ground) in the radial direction. This paper reports a preliminary formulation and presents some initial computational results for the sound fields above and below a porous ground. The numerical results from the PE calculations were compared with the results obtained from analytical solutions for and other benchmark results. A linear and cubic Hermite interpolate function was used in the numerical formulations for the finite element model. It has been shown that use of the cubic Hermite interpolation function generally leads to more accurate numerical solutions with fewer elements. [Work partially funded by Federal Aviation Administration and the China Research Scholarship Council.]