Jeffrey Phillip Mcateer

Practical applications of first‐ and second‐order differential microphones in personal computer (PC) multimedia products.

Directional microphones are used in PC voice and telephony applications to reduce the pickup of noise and reverberation, as well as reduce loudspeaker‐to‐microphone acoustic coupling. Differential‐type directional microphones are popular because of their small size and relatively low cost. This talk focuses on how differential microphone technology has been used in new products and solutions developed by AT&T intelligent acoustic systems for the PC multimedia industry.

Talker direction finder system implemented with cardioid beams and DSP algorithm.

A prototype talker direction finder (TDF) algorithm has been developed that will rapidly locate a new talker (within 200–400 ms) or track a moving one. For most room configurations, the algorithm has an inaccuracy mean of less than 10° of azimuthal angle and a standard deviation of 7°. The TDF provides full room, 360° coverage. A prototype where the TDF physically rotates a camera toward the talker has demonstrated the TDF’s robustness in difficult (i.e., realistic) noisy and reverberant environments. The physical inputs to the TDF are three small and inexpensive omnidirectional microphone elements that are all placed within a 1‐in. circle, allowing inconspicuous design into a consumer product. Three μ‐law codecs provide Inputs to the digital signal processor where the TDF’s new least‐mean‐squares‐type adaptive algorithm resides. The overall system design is summarized, including preprocessing to reduce the effects of noise and reverberation. The adaptive algorithm, which employs redundant ‘‘pattern matching’’ to six cardioid acoustic pickup beams formed from the three microphone element inputs, is then presented. The TDF can provide enhanced solutions for teleconferencing and speakerphone acoustic systems. The algorithm could be used to provide directional information to steer an ‘‘adaptive beamformer’’ for advanced audio pickup applications.