| 摘要 |
Disclosed is an automatically tunable notch filter and method for suppression of acoustical feedback in an audio signal. The apparatus includes a selectively tunable notch filter having a center frequency which is variable over at least a substantial portion of the audio frequency spectrum. The apparatus receives an audio signal which is substantially non-periodic in the absence of acoustical feedback and substantially periodic with an instantaneous dominant frequency in the presence of the same. The duration of successive periods are monitored and compared by an up/down counter to determine whether the audio input signal is substantially periodic and to determine the instantaneous dominant frequency of such audio signal. Upon detection of an audio signal which is substantially periodic, the notch filter is tuned to the instantaneous dominant frequency so as to suppress the acoustical feedback.
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