Microphone position and gain calibration for a large-aperture microphone array

• Published in: IEEE transactions on speech and audio processing Vol. 13; no. 1; pp. 42 - 52
• Main Authors: Sachar, J.M., Silverman, H.F., Patterson, W.R.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.01.2005; Institute of Electrical and Electronics Engineers
• Subjects: Acoustic measurements; Acoustics; Applied sciences; array processing; Arrays; Calibration; Channels; Costs; Electrets; Exact sciences and technology; Gain; Gain measurement; Information, signal and communications theory; locations; Microphone arrays; microphone positions; Microphones; Noise levels; Position measurement; Signal processing; Speech; Speech processing; Telecommunications and information theory; Teleconferencing; Time measurement; array processing; Microphone; Acoustic measurement; Audio signal processing; Array signal processing; microphone arrays; Calibration; microphone positions; Acoustic measurements; locations; Localization; Speech processing; Gain
• ISSN: 1063-6676; 1558-2353
• DOI: 10.1109/TSA.2004.834459

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 computing is rapidly approaching the point at which these arrays will be practical in many common environments. However, an important issue is the calibration of an array. We discuss procedures to accurately determine both the coordinates in three-dimensions for the position of each microphone and the individual gains of each microphone/microphone channel. For the positions, we found that calibration by direct measurement, using a surveyor's transit, is simply too error prone, time consuming, and difficult for large arrays and is too inaccurate for small arrays. We have also seen that without the careful matching of inexpensive electret microphones, the channel sensitivities vary by as much as 6 dB and performance can be enhanced by suitable compensation. This paper describes new apparatus and techniques for automatic calibration using acoustic signals. Experimental results using both small and large-aperture microphone array systems show the acoustically-determined positions to be more consistent than the ones measured directly. Gain measurements are somewhat more difficult but gains can be found within 1-2 dB with reasonable care.