Speech Intelligibility of Microphone Arrays in Reverberant Environments with Interference

Abstract

It is known that speech intelligibility degrades with additive noise and reverberation, and that quantitative parameters such as fidelity and signal-to-noise ratio can be improved by using microphone arrays with various beamforming algorithms. However, it is not clear how the array configuration impacts the intelligibility of speech. Numerical experiments, using widely-used models, provide the most convenient comparison, and the approach allows rapid assessment of parameters such as the array configuration, the number and spacing of the elements, and modeled features such as room reflection coefficients. For a typical reverberant room with a single wanted source and two unwanted sources (interferers), we compare the performance of two ceiling-mounted configurations - the uniform linear array (ULA) and a uniform circular array (UCA). The microphones are taken as omnidirectional and equispaced along the array loci, and we use a standard gain-constrained power minimization beamformer. In this study, a limiting performance is presented by emphasizing the early reflections over the late ones for the prior steering vector. Under this steering vector condition, for the same number of elements, the UCA easily outperforms the ULA on known quality and intelligibility metrics. For both arrays in this room scenario, all the metrics increase with an increasing number of microphones, although for one intelligibility metric, diminishing returns set in at about 12 microphones.