A method of timbral equalization for Ambisonics reproduction with irregular loudspeaker configuration

Abstract

Ambisonics is a spatial sound reproduction technique based on spatial harmonics decomposition and each order approximation of target sound field. Given a spatial region, Ambisonics is able to reconstruct target sound field accurately up to a frequency limit imposed by Shannon–Nyquist spatial sampling theorem. Above that limit, spatial aliasing in reconstructed sound field occurs, and therefore, timbre equalization in loudspeaker signals is needed to reduce perceived timbre coloration in reproduction. Power equalization is a common and effective method in which the overall power of loudspeaker signals are equalized to be independent of target source direction. The power equalization can be easily implemented in the Ambisonics reproduction with regular rather than loudspeaker configuration. In this study, a method of power equalization for Ambisonics reproduction with irregular loudspeaker configuration is proposed. The fluctuation of overall power of loudspeaker signals with target source direction is controlled within 3 dB by appropriate choice of the decoding coefficients of higher-order spatial harmonics in Ambisonics reproduction. This method is applicable to Ambisonics signals obtained by simulation or microphone array recording. Psychoacoustic experiments indicate that the current method reduces the timbral coloration to some extent while keeps the localization performance in reproduction.