Radial filters for near field source separation in spherical harmonic domain

Abstract

Radial filter design for processing near field speech sources over a spherical microphone array is challenging. Polynomial based radial filter design procedures have been proposed in earlier work. In this paper we address the issue of radial filter design using a family of orthogonal polynomials called the Gegenbauer polynomials. The radial filters designed using this approach indicate an improved radial response and greater efficiency in attenuating distant sources. Improved white noise gain and directivity index are also noted from experimental evaluations. The radial filters hence designed are used to separate directionally co-incident near field speech sources. Subjective evaluation is conducted on separated sources using measures like LSD, PESQ, and SDR. The subjective evaluation scores are motivating enough to be considered for practical speech and audio applications.