'SYSTEM AND METHOD FOR DUAL MICROPHONE SIGNAL NOISE REDUCTION USING SPECTRAL SUBTRACTION'

摘要

SPEECH ENHANCEMENT IS PROVIDED IN DUAL MICROPHONE NOISE REDUCTION BY INCLUDING SPECTRAL SUBTRACTION ALGORITHMS USING LINEAR CONVOLUTION, CAUSAL FILTERING AND/OR SPECTRUM DEPENDENT EXPONENTIAL AVERAGING OF THE SPECTRAL SUBTRACTION GAIN FUNCTION. ACCORDING TO EXEMPLARY EMBODIMENTS, WHEN A FAR-MOUTH MICROPHONE (586) IS USED IN CONJUCTION WITH A NEAR-MOUTH MICROPHONE (584), IT IS POSSIBLE TO HANDLE NON-STATIONARY BACKGROUND NOISE AS LONG AS THE NOISE SPECTRUM CAN CONTINUOUSLY BE ESTIMATED FROM A SINGLE BLOCK OF INPUT SAMPLES. THE FAR-MOUTH MICROPHONE (586), IN ADDITION TO PICKING UP THE BACKGROUND NOISE, ALSO PICKS UP THE SPEAKER'S VOICE, ALBEIT AT A LOWER LEVEL THAN THE NEAR-MOUTH MICROPHONE (584). THE ENHANCE THE NOISE ESTIMATE, A SPECTRAL SUBTRACTION STAGE (601) IS USED TO SUPRESS THE SPEECH IN THE FAR-MOUTH MICROPHONE SIGNAL.TO BE ABLE TO ENHANCE THE NOISE ESTIMATE, A ROUGH SPEECH ESTIMATE IS FORMED WITH ANOTHER SPECTRAL SUBSTRACTION STAGE (602) FROM THE NEAR-MOUTH SIGNAL. FINALLY, A THIRD SPECTRAL SUBSTRACTION FUNCTION (603) IS USED ENHANCED BACKGROUND NOISE ESTIMATE. A CONTROLLER (604) DYNAMICALLY DETERMINES ANY OR ALL OF A FIRST, SECOND, AND THIRD SUBTRACTION FACTOR FOR EACH OF THE FIRST, SECOND, AND THIRD SPECTRAL SUBSTRATION STAGES (601,602,603), RESPECTIVELY.(FIG.6)