| 摘要 |
AN ECHO REMOVING APPARATUS FOR REDUCING THE ECHO CAUSED BY SOUND GENERATED TURNING FROM A SPEAKER ROUND TO A MICROPHONE OF A SMALL-SIZED SOUND GENERATED COMMUNICATION TERMINAL, SUCH AS A PORTABLE TELEPHONE. A SPEAKER OUTPUT SIGNAL X(K), SENT FROM A TERMINAL (11) TO A SPEAKER (12), IS SENT TO A SMOOTHED POWER VALUE CALCULATION CIRCUIT (21)OF A TAP COEFFICIENT ESTIMATION CIRCUIT(21)WHERE A SMOOTHED INPUT SIGNAL POWER VALUE PX (K), WHICH IS A SMOOTHED VERSION OF THE SQUARE SUM VALUES, IS FOUND AND SENT TO A TAP COEFFICIENT UPDATING CIRCUIT(22). USING THE SMOOTHED INPUT SIGNAL POWER VALUE PX (K), THE TAP COEFFICIENT UPDATING CIRCUIT(22) UPDATES TAP COEFFICIENTS OF A FILTER(15) THE FILTER (15) FILTERS THE SPEAKER OUTPUT SIGNAL X(K) TO OUTPUT A PSEUDO ECHO SIGNAL WHICH IS SENT TO A SUBTRACTOR (14)WHERE IT IS SUBTRACTED FROM A MICROPHONE INPUT SIGNAL COLLECTED BY A MICROPHONE (13). THE FILTER TAP COEFFICIENTS MAY BE PROHIBITED FORM BEING FLUCTUATED AND ECHO REMOVING CHARACTERISTICS OF THE ECHO REMOVING APPARATUS MAY BE STABILIZED WITHOUT INCREASING THE PROCESSING VOLUME FOR TAP COEFFICIENT ESTIMATION (FIG. 5)
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