| 摘要 |
<P>PROBLEM TO BE SOLVED: To attain response 1 kHz using digital control technology, to automatically adjusting product variation of control loop gain and to precisely adjust the control loop gain without being influenced by surrounding noise in a noise cancellation headphone. <P>SOLUTION: The noise cancellation headphone is constituted by providing: a feedback loop which collects voice from a loudspeaker 44 and the surrounding noise by a microphone 46 to perform feedback and reproduces the voice from the loudspeaker 44 according to a deviation signal with a music signal; a variation adjustment means for adjusting a gain of a digital filter 41 provided to the feedback loop to adjust an open loop gain; a means for setting a pass frequency band of the digital filter 41 to a first frequency band of which the noise should be canceled in the case of listening to the voice in a noise cancellation mode and a means for setting the pass frequency band to a second frequency band within the first frequency band and which is narrower than the first frequency band in the case of variation adjustment. <P>COPYRIGHT: (C)2007,JPO&INPIT |
