Voice source localization for automatic camera pointing system in videoconferencing

This paper describes the voice source localization algorithm used in the PictureTel automatic camera pointing system (LimeLight/sup TM/, dynamic speech locating technology). The system uses an array of 46 cm wide and 30 cm high, which contains 4 microphones, and is mounted on top of the monitor. The three dimensional position of a sound source is calculated from the time delays of 4 pairs of microphones. In time delay estimation, the averaging of signal onsets of each frequency band is combined with phase correlation to reduce the influence of noise and reverberation. With this approach, it is possible to provide reliable three dimensional voice source localization by a small microphone array. Post processing based on a priori knowledge is also introduced to eliminate the influences of reflections from furniture such as tables. Results of speech source localization under real conference room conditions are given. Some system related issues are also discussed.