Sound Zones: On Envelope Shaping of FIR Filters

Sound zones, i.e. spatially confined regions of individual audio content, can be created by appropriate filtering of the desired audio signals reproduced by an array of loudspeakers. The challenge of designing filters for sound zones is twofold: First, the filtered responses should generate an acoustic separation between the control regions. Secondly, the pre- and post-ringing as well as
spectral deterioration introduced by the filters should be minimized. The tradeoff between acoustic separation and filter ringing is the focus of this paper. A weighted L2-norm penalty is introduced in the sound zones optimization problem, to reduce pre- and post-ringing of the filters. The effect of shaping the filter envelopes is investigated in an experimental setup with eight woofers,
surrounding two control regions. The results show that it is possible to reduce the pre- and postringing of the filters without significantly reducing the acoustic separation between the zones.