Application of time-domain near-field acoustical holography to the high-order ambisonics presentation of moving sound sources

Abstract

High-order ambisonics (HOA) is a sound field reproduction method based on results from near-field acoustical holography (NAH). As such, it is formulated in the frequency domain; this assumes a stationary acoustic field. This presentation applies a recent time-domain formulation of NAH by Attendu and Ross. The approach is based on the linear deconvolution along the spatial coordinates and samples the Green's function in the time and spatial domains, as opposed to the Fourier domain. Our contribution is an application of these ideas to overcome the problems inherent in the HOA reproduction of non-stationary sound fields, in particular those of moving sound sources. In practice, the rendering of moving sound sources is approximated by assuming they are stationary within short temporal windows. The approximation, while useful for slow-moving sources, cannot re-create the Doppler shift and results in discontinuities along the temporal structure of the sound field. On the other hand, the proposed method does not impose any constraints on the motion of the sound sources. Unlike conventional HOA, the proposal cannot be formulated as a simple filter bank; however, numerical experiments show that fast moving sources exhibit the expected Doppler shift.