| 摘要 |
METHOD AND APPARATUS FOR ACHIEVING ECHO SUPPRESSION IN COMMUNICTIONS SYSTEMS INCLUDE AN ECHO SUPPRESSOR, REFERREDTO HEREIN AS AN AC-CENTER ATTENNUATOR, WHICH ATTENUATES THE ECHO COMPONENT OF A COMMUNICATIONS SIGNAL BY MULTIPLYING A PORTION OF THE COMMUNICATIONS SIGNAL BY AN APPROPRIATE SCALE FACTOR, SPECIFICALLY, THE AC-CENTER ATTENUATOR SCALES THAT PORTION OF THE COMMUNICATIONS SIGNAL LYING WITHIN A SLIDING ATTENUATION WIMDOW. THE ATTENUATION WINDOW TRACKS THE COMMUNICATIONS SIGNAL SO THAT THE AC-CENTER ATTENUATOR SUPPRESSES THE ECHO COMPONENT WHILE PASSING OTHER SIGNAL COMPONENTS OF INTEREST (e.g., NEAR-END SPEECH AND NOISE). THE SCALE FACTOR WITHIN THE ATTENUATION WINDOW, AND THE SIZE OF THE ATTENUATION WINDOW ITSELF, ARE DYNAMICALLY ADJUSTED SO THAT THE AC-CENTER ATTENUATOR INTRODUCES MINIMUM SIGNAL DISTORTION AND FEW AUDIBLE ARTIFACTS. THE DYNAMIC ADJUSTMENT IS CARRIED OUT TO PROVIDE A DESIRED ROUND-TRIP ECHO GAIN IN A SYSTEM IN WHICH THE AC-CENTER ATTENUATOR IS IMPLEMENTED. TOWARD THAT END, A MEASURE OF THE ECHO ATTENUATION ACHIEVE BY AN ECHO SUPPRESSOR (e.g., AN ADAPTIVE ECHO CANCELER) IS OBTAINED BY COMPUTING A RATIO OF FIRST AND SECOND VALUES, WHEREIN THE FIRST AND SECOND VALUES INDICATE ENERGY LEVELS IN THE ECHO SUPPRESSOR OUTPUT AND INPUT SIGNALS, RESPECTIVELY. ALTERNATELY, THE ECHO ATTENUATION ACHIEVED BY A BLOCKWISE-UPDATING ECHO CANSELER IS OBTAINED BY COMPUTING A RATIO OF FIRST AND SECOND VALUES, WHEREIN THE FIRST VALUE INDICATES A LEVEL OF ENERGY IN A SET OF UPDATE COEFFICIENTS OF THE ECHO CANCELER AND THE SECOND VALUE INDICATES A LEVEL OF ENERGY IN THE ECHO CANSELER INPUT SIGNAL. IN EACH CASE, THE COMPUTED RATIO CAN BE USED TO ADJUST THE LEVEL OF ATTENUATION PROVIDED BY A RESIDUAL ECHO SUPPRESOR.FIG. 5
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