Theory and perceptual evaluation of the binaural reproduction and beamforming tradeoff in the generalized spherical array beamformer

Microphone arrays are widely used in speech enhancement systems for noisy and reverberant environments. Recently, a generalized spherical array beamforming approach was developed incorporating binaural sound reproduction in the beamforming process. This generalized spherical array beamformer (GSB) maintains the spatial information through the binaural cues and improves both the spatial realism and the speech intelligibility. In this paper, the theory of the tradeoff that arises when incorporating both beamforming and binaural reproduction in a single array is developed and investigated through a simulation study and a listening test. By representing the GSB formulation in matrix form for investigating the single plane-wave scenario, two measures are developed in order to evaluate the performance of the GSB in terms of both binaural reproduction and spatial selectivity. These measures are then employed in the evaluation of the performance of various GSB beam-patterns using simulations. A listening test experiment that validates the simulation results is then reported. Results validate the theory, i.e., the GSB can be used to integrate successfully binaural reproduction and beamforming, allowing the user to emphasize either of the two, but with a clear tradeoff; improving one is only possible at the expense of degrading the other.