A time-variant impulse response method for acoustic scattering from moving two-dimensional surfaces

A time-variant impulse response method is proposed, developed, tested, and shown to provide new insights into different scattering problems involving moving surfaces. The method proposed is general, conceptually straightforward, and can accommodate moving sources and receivers. While the time-variant impulse response method has been developed specifically in this study to extend the capability of the wedge assemblage (WA) model [e.g., R.S. Keiffer and J.C. Novarini, J. Acoust. Soc. Am. 107, 27-39 (2000)], the framework can be applied to other scattering models including those based in the frequency domain. Calculations involving moving periodic surfaces and moving receivers are presented and compared with good results to a generalized grating equation and small wave-height approximation perturbation theory. The time-variant impulse response model is also applied to time-evolving sea surfaces, and the previously published results of Pourkaviani and Willemsen [J. Acoust. Soc. Am. 90, 426-432 (1991)] are confirmed. It is also shown that windward-oriented backscatter geometries can lead to a Doppler spectrum that peaks at higher than expected Doppler shifts.