Assessment of time-domain equivalent source method for acoustic scattering

Equivalent source methods have been applied in the frequency and time domain to provide a fast and efficient computation for acoustic scattering. Although the advantages and capabilities of the method have been demonstrated, the limitations and drawbacks of the method have not yet been explored in detail. A detailed understanding of the equivalent source method is needed to use the method in a wide range of applications with more confidence. This paper presents an initial assessment of an application of the time-domain equivalent source method to the prediction of acoustic scattering. The sensitivity of the method to numerical parameters, including the number of the surface collocation points, the number and position of the equivalent sources, the time step, and the cutoff singular value, is investigated, and suggestions for these parameters are given for accurate predictions. A numerical instability issue is shown, and a way to stabilize the solution with a time-averaging scheme is introduced. The sound power is calculated using the equivalent source strength to demonstrate the redistribution of the sound intensity by a scattering body and the conservation of the total sound power. Finally, scattering of sound from a source in a short duct is tested to demonstrate the utility of the tool for a more complicated shape of the scattering surface.