| 摘要 |
<P>PROBLEM TO BE SOLVED: To suppress the output of a high frequency control sound when an A/D converter for A/D-converting a signal output from a microphone is saturated. Ž<P>SOLUTION: A feedback type active muffler having the microphone 24 for detecting a noise, a speaker 23 for outputting a control sound for canceling the noise, the A/D converter 32 for A/D-converting the output of the microphone 24 to generate a detection signal ej, a reference signal generation part 102 for removing the components of the control sound from the detection signal ej to compute a reference signal xj and a noise control filter 103 for generating a control sound signal uj for driving the speaker 23 from the reference signal xj includes a noise level determination part 106 for comparing the detection signal ej with a threshold a1 not higher than the saturation level of the A/D converter 32 to generate a determination signal, and an output control part 107 for suppressing the output of the control sound according to the determination signal. This suppresses the output of an unnecessary control sound when a loud noise is detected. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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