An integrated circuit for implementing at least a portion of a personal audio device, comprising: an output adapted to provide an output signal to an output transducer (SPKR) including both source audio for playback to a listener and an anti-noise signal for countering the effects of ambient audio sounds in an acoustic output of the transducer (SPKR); at least one microphone input adapted to receive at least one microphone signal indicative of the ambient audio sounds and that contains a component due to the acoustic output of the transducer (SPKR); and a processing circuit (20, 30) configured to adaptively generate the anti-noise signal to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit (20, 30) implements an adaptive filter having a response that shapes the source audio and a combiner that removes the shaped source audio from the at least one microphone signal to provide a corrected microphone signal, wherein the processing circuit (20, 30) is configured to determine a relative magnitude of a source audio component of the acoustic output of the transducer (SPKR) present in the at least one microphone signal and the ambient audio sounds present in the at least one microphone signal, wherein the processing circuit (20, 30) is configured to determine a degree of coupling between the transducer (SPKR) and an ear of the listener, and wherein the processing circuit (20, 30) is configured to take action to prevent improper adaptation of the adaptive filter in response to determining that the relative magnitude of the source audio component of the acoustic output of the transducer (SPKR) present in the at least one microphone signal to the ambient audio sounds present in the at least one microphone signal indicates that the adaptive filter may not adapt properly; characterised in that the processing circuit (20, 30) is configured to adjust the determined relative magnitude of the source audio component of the acoustic output of the transducer (SPKR) present in the at least one microphone signal and the ambient audio sounds present in the at least one microphone signal in conformity with the determined degree of coupling. an output adapted to provide an output signal to an output transducer (SPKR) including both source audio for playback to a listener and an anti-noise signal for countering the effects of ambient audio sounds in an acoustic output of the transducer (SPKR); at least one microphone input adapted to receive at least one microphone signal indicative of the ambient audio sounds and that contains a component due to the acoustic output of the transducer (SPKR); and a processing circuit (20, 30) configured to adaptively generate the anti-noise signal to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit (20, 30) implements an adaptive filter having a response that shapes the source audio and a combiner that removes the shaped source audio from the at least one microphone signal to provide a corrected microphone signal, wherein the processing circuit (20, 30) is configured to determine a relative magnitude of a source audio component of the acoustic output of the transducer (SPKR) present in the at least one microphone signal and the ambient audio sounds present in the at least one microphone signal, wherein the processing circuit (20, 30) is configured to determine a degree of coupling between the transducer (SPKR) and an ear of the listener, and wherein the processing circuit (20, 30) is configured to take action to prevent improper adaptation of the adaptive filter in response to determining that the relative magnitude of the source audio component of the acoustic output of the transducer (SPKR) present in the at least one microphone signal to the ambient audio sounds present in the at least one microphone signal indicates that the adaptive filter may not adapt properly; characterised in that the processing circuit (20, 30) is configured to adjust the determined relative magnitude of the source audio component of the acoustic output of the transducer (SPKR) present in the at least one microphone signal and the ambient audio sounds present in the at least one microphone signal in conformity with the determined degree of coupling.