Microphone arrays fundamentals

Microphone arrays are essentially directional sensors. They are therefore mainly used for locating, identifying, isolating, measuring and recording individual sound sources. The main principles governing the directivity of microphone arrays are reviewed: phase differences between signals create constructive and destructive interferences, depending on the direction of the sound source. Moreover, signal processing is applied to provide “beamforming”, i.e. beam shaping and steering. Contrary to continuous antenna, discrete arrays can create aliasing, which can result in false detections of sound sources. The delay-and-sum and filter-and-sum beamformers are described. Finally, as simple beamformers are often frequency dependent, some solutions to obtain constant (broad-band) directivity are presented.