Microphone array systems for hands-free telecommunication

Microphone array systems can be effective in combating the detrimental effects of acoustic noise and reverberation in hands-free telecommunication. This paper discusses classical delay-sum beamformers as well as the more general filter-sum beamformers. Filter-sum beamformers add the ability to control the array beampattern as a function of frequency and a new design method for a constant beamwidth filter-sum beamformer is presented. The delay-sum and filter-sum beamformers require array sizes that are comparable to the acoustic wavelength. These designs can result in arrays that are large in size. For applications that are space constrained, differential microphone array systems are presented. Finally, two types of adaptive beamformers are presented: a broadside array and a two-element differential microphone.