A comparison of modal and spatially matched-filter beamforming for rigid spherical microphone arrays in the context of data-based binaural synthesis

Abstract

Several approaches to data-based binaural synthesis have been published that capture a sound field by means of a spherical microphone array. The captured sound field is decomposed into plane waves, which are auralized using (far-field) head-related impulse responses (HRIRs). In practice, the decomposition into plane waves is performed by beamforming. A well-known technique for spherical microphone arrays is modal beamforming where the sound field is represented with respect to surface spherical harmonics. A numerically stable approximation is the spatio-temporal matched-filter technique. Here the acoustic reciprocity theorem is used in conjunction with the matched filter technique for beamforming. This paper reviews the matched filter beamformer and compares its properties to the modal beamformer in a realistic scenario. The performance of the two beamforming techniques is compared in the context of data-based binaural synthesis. Time-domain properties of the resulting ear-signals, as well as suitable binaural measures, are investigated for simulated and captured scenarios.