Personal Sound Zones: Delivering interface-free audio to multiple listeners

Abstract

Sound rendering is increasingly being required to extend over only certain regions of space for multiple listeners, known as personal sound zones, with minimum interference to listeners in other regions. In this article, we present a systematic overview of the major challenges that have to be dealt with for multi-zone sound control in a room. Sound control over multiple zones is formulated as an optimisation problem and a unified framework is presented to compare two state-of-the-art sound control techniques. While conventional techniques have been focusing on point-to-point audio processing, we introduce wave-domain sound field representations and active room compensation for sound pressure control over a region of space. The design of directional loudspeakers is presented and the advantages of using arrays of directional sources are illustrated for sound reproduction, such as greater control of sound fields over wide areas and reduced total number of loudspeaker units, thus making it particularly suitable for establishing personal sound zones.

On the feasibility of personal audio systems over a network of distributed loudspeakers

“…In this sense, the vectors g mk could be seen as 'effort' vectors that can help the system to deal with a given acoustic coupling. On the other hand, if s i (n) were single-frequency signals, g mk could be seen as the set of coefficients needed to build signals v l,k (n) (2) in order to maximize the 'acoustic contrast' [1], [8], which in our case would be defined as the SINR in (11).…”

“…Recently Betlehem et al [1] presented an interesting overview of the major challenges that multizone sound control in a room has to deal with. One of the first approaches to this problem is based on the maximization of a contrast function between the bright zone (where the sound is presented) and the dark or silent zone, which converts the multizone problem in an optimization problem [2].…”

Reproducing personal sound zones using a hybrid synthesis of dynamic and parametric loudspeakers

“…The crossover frequencies are the vertical dash-dot black lines which clearly indicate the point where ζ MSR (k) begins to decrease due to spatial aliasing. Note that the multizone occlusion problem [1], [11] (should it occur) may be difficult to overcome with one PL, however, the MSR grating lobes interfere less over D q during this phenomenon. Also shown in Fig.…”

“…Personal sound environments, such as provided by multizone soundfield reproduction (MSR) [1] and parametric loudspeakers (PL) [2], are of interest in applications such as vehicle cabin entertainment/communication systems, cinema surround sound systems, multi-participant teleconferencing and personal audio in restaurant/cafés. As well as creating a target bright zone, it is sometimes also desired to create a second, quiet zone.…”

“…A method [4] was proposed later, in 2002, to maximise the ratio of energy between two regions which was termed Acoustic Contrast Control [1]. Afterwards, earlier multizone reproduction techniques made use of least-squares pressure matching [5] and cylindrical harmonic expansion [6].…”