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.

Microphone arrays are used in speech signal processing applications such as teleconferencing and telepresence, in order to enhance a desired speech signal in the presence of speech signals from other speakers, reverberation and background noise. These arrays usually provide a single-channel output, so that no spatial information is available in the output signal. However, spatial information on the sound sources may increase the intelligibility of a speech signal perceived by a human listener. This work presents a mathematical framework for generalized spherical array beamforming that in addition to suppressing noise and reverberation, is aiming to preserve spatial information on the sources in the recording venue. The generalized beamforming, formulated in the spherical harmonics domain, is based on binaural sound reproduction where the head-related transfer functions are incorporated into a headphones presentation. The performance of the proposed generalized beamformer is compared to that of a single-channel output maximum-directivity beamformer. Listening tests with human subjects show that when the generalized beamformer is used the intelligibility is improved at low input SNRs.

Currently employed microphone arrays usually have a single-channel output, such that no spatial information can be perceived by a human listener. However, spatial information may trigger spatial mechanisms in the human auditory system which can improve the intelligibility. This work presents a mathematical framework for the binaural beamforming approach for the ideal and order-limited representation in the spherical harmonics domain. The performance of the proposed binaural beamformer is compared to that of a monaural maximum directivity beamformer using objective signal-based measures and subjective listening tests. It is shown that using the binaural beamformer results in higher intelligibility than the monaural beamformer.