Spatial Sampling of Binaural Room Transfer Functions for Head-Tracked Personal Sound Zones

The spatial sampling of binaural room transfer functions that vary with listener movements, as required for rendering personal sound zone (PSZ) with head tracking, was experimentally investigated regarding its dependencies on various factors. Through measurements of the binaural room transfer functions in a practical PSZ system with either translational or rotational movements of one of the two mannequin listeners, the PSZ filters were generated along the measurement grid and then spatially downsampled to different resolutions, at which the isolation performance of the system was numerically simulated. It was found that the spatial sampling resolution generally depends on factors such as the moving listener’s position, frequency band of the rendered audio, and perturbation caused by the other listener. More specifically, the required sampling resolution is inversely proportional to the distance either between two listeners or between the moving listener and the loudspeakers and is proportional to the frequency of the rendered audio. The perturbation caused by the other listener may impair both the isolation performance and filter robustness against movements. Furthermore, two crossover frequencies were found to exist in the system, which divide the frequency band into three sub-bands, each with a distinctive requirement for spatial sampling.