Position calibration of large-aperture microphone arrays

Large-aperture microphone arrays have the potential for providing quality speech acquisition from multiple talkers over a large focal area for such applications as teleconferencing and speech-recognition input. The cost of supporting computing technology is quickly approaching the point in which these arrays will be practical in many common environments. However, an important issue is the calibration of an array that has been instal1ed in some medium-sized to large room. By calibration, we mean the determination of the precise set of coordinates in three-dimensions for the positions of the microphones. Calibration by direct measurement or even by a ´laser transit is simply too error-prone, time-consuming and painful. This paper describes new apparatus and techniques for automatic calibration using acoustic signals. Experimental results using our large-aperture microphone array system show the automatical1y-determined positions to be even more consistent than the ones measured directly. The paradigm for using the apparatus and technique most advantageously is also presented.