Directional microphones are spatial filters that can be designed to improve the sound quality of speech in audio telecommunication. At present, the most common type of directional microphone utilized in audio telecommunication is a simple first-order differential microphone having a hypercardioid directivity pattern. The directivity index (microphone gain in isotropic noise) for the hypercardioid microphone is 6 dB. For very noisy and reverberant environments more directional gain will be necessary. This talk will describe and discuss some of the microphone array systems that have been proposed in the last decade that address this problem.