High order Ambisonic decoding method for irregular loudspeaker arrays

Ambisonics, a sound field synthesis and reproduction technique, has shown promising results in conveying three-dimensional spatialized sound. Ambisonic encodings directly describe the spatial properties of sound fields without reference to the reproduction system. Precise regeneration of a sound field requires a large number of loudspeakers arranged so as to adequately sample all directions; this is referred to as a regular layout. It is not difficult to find a decoding matrix to reproduce Ambisonic recordings using uniformly distributed loudspeakers. Nevertheless, evenly locating a large number of loudspeakers is not feasible in most scenarios. Irregular arrays, however, are known to lead to ill-conditioned and singular re-encoding matrices. We propose a method for accurate reproduction of high order Ambisonic recordings over irregular loudspeaker arrays. Our approach consists of three stages which aim to exploit any regularities of the array, while using asymmetrically located loudspeakers to expand the listening volume. We evaluated our proposal using an irregular 157-channel loudspeaker array. Comparisons with mainstream decoding methods were conducted. The proposed scheme results in an overall increase in the size of the listening volume.