Soundfield navigation using an array of higher-order ambisonics microphones

Abstract

A method is presented for soundfield navigation through estimation of the spherical harmonic coefficients (i.e., the higher-order ambisonics signals) of a soundfield at a position within an array of two or more ambisonics microphones. An existing method based on blind source separation is known to suffer from audible artifacts, while an alternative method, in which a weighted average of the ambisonics signals from each microphone is computed, is shown to necessarily introduce comb-filtering and degrade localization for off-center sources. The proposed method entails computing a regularized least-squares estimate of the soundfield at the listening position using the signals from the nearest microphones, excluding those that are nearer to a source than to the listening position. Simulated frequency responses and predicted localization errors suggest that, for interpolation between a pair of microphones, the proposed method achieves both accurate localization and minimal spectral coloration when the product of angular wavenumber and microphone spacing is less than twice the input expansion order. It is also demonstrated that failure to exclude from the calculation those microphones that are nearer to a source than to the listening position can significantly degrade localization accuracy.