Personal sound zones in the short-time Fourier transform domain with relaxed reverberation

Personal-sound-zones (PSZ) techniques deliver independent sounds to multiple zones within a room using a loudspeaker array. The target signal for each zone is clearly audible within that zone while inaudible or non-distracting in others, assured by applying pre-filters to the loudspeaker array. The pre-filters are traditionally designed with time-domain or frequency-domain methods, which suffer from high computational complexity and large system latency, respectively. This work proposes a subband pressure-matching method in the short-time Fourier transform domain using the convolutive transfer function approximation, termed CTF-PM. The proposed method considerably reduces computational complexity relative to time-domain methods and existing subband methods, while maintaining low system latency. Additionally, CTF-PM achieves similar performances in acoustic contrast and normalized mean square error compared to baseline methods. Moreover, by introducing a weighting vector on the reproduction error, a relaxed-reverberation framework is incorporated into CTF-PM. This framework aims for an accurate reproduction of the decaying rate instead of the random samples of the reverberations, improving the acoustic contrast of the PSZ system while preserving the perceptual experience. Our experiments demonstrated that the relaxed-reverberation framework improved broadband acoustic contrast in the 0-2 kHz range by more than 3 dB, without degrading the perceptual experience.