| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide occurrence of howling when a speaker is far from a microphone to cause the howling. Ž<P>SOLUTION: A pseudo noise signal to be generated by an M series generator 11 is output to the outside of the microphone via an output part 15, and emitted from the speaker which is not illustrated. A correlation computation part 23 computes mutual correlation between the pseudo noise signal to be generated by the M series generator 11 and a sound signal to be obtained via a microphone element 1. A distance computation part 24 computes delay time with a section where the mutual correlation with the pseudo noise signal becomes the peak in the pseudo noise signal and the sound signal to be obtained via the microphone element 1 based on a computation result of the mutual correlation to be converted into sound propagation distance. A gain control part 33 performs gain control for sound for reducing gain of a sound volume 5 as the distance computed by the distance computation part 24 becomes smaller than a threshold. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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