| 摘要 |
PROBLEM TO BE SOLVED: To prevent excessive amplification of a signal of frequency that is affected by an unstable zero point and then to prevent the singing phenomena or the breakage of a loudspeaker by generating the speaker input signals via a band-stop filter, having its variable characteristic and a convolver which is cascaded to the filter. SOLUTION: A band-stop filter 1 having its variable characteristic and a covolver 2 which is cascaded to the filter 1 generate loudspeaker input signals. The frequency that is affected by an unstable zero point is defined as the band- stop frequency of the filter 1 to prevent the signal of the above frequency from being amplified excessively by the convolver 2. Then the singing phenomena of the breakage of a speaker can be prevented, and the desired characteristics are attained for the signals of other frequencies. The band-stop frequency is detected, based on an error signal e(n) between a reference signal d(n) generated by a reference signal generation filter and a replica c(n) of the signal d(n) which is generated by an adaptive filter 5 and also on a prescribed frequency average power ratio. |
