| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent increase of noise in a band other than a band in which noise is to be reduced, when noise is reduced by generating signals collected by a microphone from a speaker unit. Ž<P>SOLUTION: A signal collected by a microphone 1 is supplied to an adder 4c of an adding part 4 through a microphone amplifier 8 and a bandpass filter 3. The output signal of the adding part 4 is supplied to a speaker unit 2 through an amplifier 5. Since sound waves having a phase reverse to that of the noise are radiated from the speaker unit 2, the sound waves of the speaker and the noise at the position of the microphone 1 are negated with each other. A signal extracted by a microphone 6 arranged in a null area of the speaker unit 2 is supplied to the adder 4c of the adding part 4 through a microphone amplifier 9 and a bandpass filter 7, and noise increased by noise canceling is canceled. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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