Simulation of ground impedance in finite difference time domain calculations of outdoor sound propagation

Abstract

The finite difference time domain (FDTD) simulation is a very promising tool to investigate sound propagation phenomena outdoors. One difficulty is the handling of boundary conditions (e.g. at the ground) which are usually described by frequency dependent complex impedances. The exact transformation into the time domain leads to a convolution operation which corresponds to a high computational effort. The paper investigates the possibility to approximate typical ground impedances by a polynomial representation of first and second order. These approximated impedances can be incorporated easily in the finite difference computational scheme at only small additional computational cost. FDTD ground effect calculations based on the approximated impedances show very good agreement with analytical solutions.