A real-time dual-microphone signal-processing system for hearing aids
Mark E. Elledge, Michael E. Lockwood, Robert C. Bilger, Marc Goueygou, Douglas L. Jones, Charissa R. Lansing, William D. O’Brien, Bruce C. Wheeler · The Journal of the Acoustical Society of America · 1999
A real-time dual-microphone-based signal-processing system has been developed that suppresses off-axis interference from multiple sound sources. The system employs optimal filtering methods to attenuate the amplitude of all signals other than that from a desired receive direction. The algorithm was implemented on a Texas Instruments TMS320C62 fixed-point digital signal-processor evaluation board installed in a PC. Input/output was accomplished via a 16-bit codec controlled by optimized assembly language routines. To simplify algorithm coding, the main algorithm was written in C and executes using approximately 55 processor time, allowing for future additions to enhance performance. It has a delay of 15 ms. The system can significantly improve the intelligibility of speech in noisy environments, as evidenced in off-line tests by a marked intelligibility weighted SNR gain [Link and Buckley, J. Acoust. Soc. Am. 91, 1662 (1992)]. Initial real-time testing with actual binaural signals supports the conclusion that this performance gain will be maintained. The results show that this system may be used as a main building block for hearing aids to be used in noisy environments. [Research supported by the Beckman Institute.]