Eulerian Time-Domain Model for Sound Propagation over a Finite-Impedance Ground Surface. Comparison with Frequency-Domain Models

An Eulerian model for sound propagation in an inhomogeneous moving medium is described. The model is based on numerical solution of the linearized Euler equations of fluid dynamics. As the model is formulated in the time domain, common acoustic boundary conditions in terms of a complex acoustic impedance cannot be used. Consequently, the model cannot be used directly for sound propagation over a finite-impedance ground surface. This problem is solved by including the ground medium in the computational system. The ground is modeled as a porous medium with a rigid frame. Numerical examples show that results of the Eulerian model are in excellent agreement with solutions of the Helmholtz equation in the frequency domain.