An integrated circuit for implementing at least a portion of a personal audio device, comprising: an output adapted to provide a signal to a 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); a reference microphone input adapted to receive a reference microphone signal (ref) from a reference microphone, the reference microphone signal (ref) being indicative of the ambient audio sounds; an error microphone input adapted to receive an error microphone signal (err) from an error microphone, the error microphone signal being indicative of the output of the transducer (SPKR) and the ambient audio sounds at the transducer (SPKR); and a processing circuit (14, 20, 30) that implements at least one adaptive filter having a response that generates the anti-noise signal from the reference signal (ref) to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit (14, 20, 30) is configured to shape the response of the at least one adaptive filter in conformity with the error microphone signal (err) and the reference microphone signal (ref) by adapting the response of the at least one adaptive filter to minimize the ambient audio sounds at the error microphone, wherein the processing circuit (14, 20, 30) is configured to detect that an ambient audio event is occurring that could cause the at least one adaptive filter to generate an undesirable component in the anti-noise signal and to change the adapting of the at least one adaptive filter in response to the detection, and wherein the processing circuit (14, 20, 30) is configured to change the adaptation of the at least one adaptive filter by halting the adaptation of the at least one adaptive filter; characterised in that: the detection that the ambient audio event is occurring includes a detection whether an indication of a variation of an overall gain of the response of the at least one adaptive filter exceeds a threshold; and the ambient audio event is a mechanical noise. an output adapted to provide a signal to a 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); a reference microphone input adapted to receive a reference microphone signal (ref) from a reference microphone, the reference microphone signal (ref) being indicative of the ambient audio sounds; an error microphone input adapted to receive an error microphone signal (err) from an error microphone, the error microphone signal being indicative of the output of the transducer (SPKR) and the ambient audio sounds at the transducer (SPKR); and a processing circuit (14, 20, 30) that implements at least one adaptive filter having a response that generates the anti-noise signal from the reference signal (ref) to reduce the presence of the ambient audio sounds heard by the listener, wherein the processing circuit (14, 20, 30) is configured to shape the response of the at least one adaptive filter in conformity with the error microphone signal (err) and the reference microphone signal (ref) by adapting the response of the at least one adaptive filter to minimize the ambient audio sounds at the error microphone, wherein the processing circuit (14, 20, 30) is configured to detect that an ambient audio event is occurring that could cause the at least one adaptive filter to generate an undesirable component in the anti-noise signal and to change the adapting of the at least one adaptive filter in response to the detection, and wherein the processing circuit (14, 20, 30) is configured to change the adaptation of the at least one adaptive filter by halting the adaptation of the at least one adaptive filter; the detection that the ambient audio event is occurring includes a detection whether an indication of a variation of an overall gain of the response of the at least one adaptive filter exceeds a threshold; and the ambient audio event is a mechanical noise.