A novel DSP system for microphone array applications

Modern digital signal processors with tens of MFLOPS/MIPS capabilities and with multiple communication channels for parallel processing have been applied to various real-time computational intensive applications. Among these, digital microphone array has been proposed for sonar, audio, teleconferencing, multi-media, and hearing aid applications. A microphone array can enhance the SNR/SIR in a noisy environment, by forming a focused beam toward the desired speech source, attenuating background noises and rejecting discrete spatial interferers. An array can also perform real time source-localization or direction-of-arrival estimation for broadband sources in various applications. We present a prototype PC-based microphone array system designed for hearing aid applications but also applicable to other tasks. A multiple channel microphone array system is described. The autonomous system's basic operations of signal-enhancement, beam formation, and detection-and-tracking are defined as processing mode, calibration mode, and search mode respectively. Algorithms for the above modes using maximum energy criterion beam formation, non-ideal microphone characteristics, and modified broadband near-field MUSIC schemes are briefly discussed. Some array performance results based on both computer simulation and real-time measurement are presented.