| 摘要 |
An integrated circuit (20) for implementing at least a portion of a personal audio device is disclosed. The integrated circuit (20) comprises an audio source having an output providing source audio for playback to a listener. A combiner (26) combines the source audio and an anti-noise signal for countering the effects of ambient audio sounds in an acoustic output of a transducer (SPKR), to generate an audio signal. A reference microphone input receives a reference microphone signal (ref) indicative of the ambient audio sounds and an error microphone input receives an error microphone signal (err) indicative of the acoustic output of the transducer (SPKR) and the ambient audio sounds at the transducer (SPKR). Further, a processing circuit (30) implements an adaptive filter having a response that generates the anti-noise signal from the reference microphone signal (ref) to reduce the presence of the ambient audio sounds heard by the listener. The processing circuit (30) implements a coefficient control block that shapes the response of the adaptive filter in conformity with the error microphone signal (err) and the reference microphone signal (ref) by adapting the response of the adaptive filter to minimize the ambient audio sounds at an error microphone. The processing circuit (30) is configured to detect whether the source audio is present at the output of the audio source, and in response to detecting that the source audio is present, to alter adaptation of the adaptive filter. |
