Spatial Multizone Soundfield Reproduction: Theory and Design

Abstract

Spatial multizone soundfield reproduction is a difficult problem, which has many potential applications. This paper provides a framework to recreate 2D spatial multizone soundfields using an array of loudspeakers. We derive the desired global soundfield by translating individual desired soundfields to a single global co-ordinate system and applying appropriate angular window functions. We reveal some of the fundamental limits of 2D multizone soundfield reproduction. We show that the ability of multizone reproduction is dependent on (i) maximum radius of multizones, (ii) window length (size, and nature), and (iii) radial distance to the furthermost zone. We illustrate the framework by designing and simulating a two dimensional two zone soundfield.

Acoustic contrast, planarity and robustness of sound zone methods using a circular loudspeaker array

“…Two main approaches have been used for sound zones. Wu and Abhayapala (2011) developed an analytical approach where the sound field coefficients of multiple zones are translated onto the global sound field. The global sound field representation allows source weights to be calculated by existing synthesis approaches such as least-squares mode matching or wave field synthesis, and the basis functions may be selected depending on the dimensionality of the problem and the source geometry.…”

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

“…The mean square error (MSE) between the desired soundfield, S d (x, k), and the actual reproduced soundfield, S a R (x, k), is [6], [20] …”

“…Due to this phenomenon, the bandwidth of reproducible soundfields with high acoustic contrast (which may be lost above the aliasing frequency) is reduced. For a part-circle array, the minimum number of dynamic loudspeakers to use before aliasing problems begin to occur is given by [6], [8] …”

“…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]. Further research has made improvements in spatial reproduction accuracy by utilising planarity [7] and orthogonal basis planewaves [8].…”

“…A fundamental issue with MSR using discrete secondary sources is that the spatial aliasing induces so-called grating lobes which can interfere across zones [10]. Recent research [6], [8], [11] suggests a full circle array of ≈ 300 loudspeakers are required to reproduce audio up to 8 kHz with high acoustic contrast.…”