A sound pick-up and reproduction system includes at least two sound sensors, such as microphones, situated at different distances from a sound reproduction device, such as a loudspeaker. A processor responds to amplitudes and phases of signals outputted by the at least two sound sensors to control a...http://www.google.com.tw/patents/US6724899?utm_source=gb-gplus-share專利 US6724899 - Sound pick-up and reproduction system for reducing an echo resulting from acoustic coupling between a sound pick-up and a sound reproduction device
