An integrated circuit for implementing at least a portion of a personal audio device, comprising: an output configured for providing an output signal to a transducer (SPKR) including both a source audio signal (ds/ia) for playback to a listener and an anti-noise signal for countering the effect of ambient audio sounds in an acoustic output of the transducer (SPKR); and a processing circuit configured for implementing an adaptive noise cancellation system configured for generating the anti-noise signal to reduce the presence of the ambient audio sounds heard by the listener by adapting, based on a presence of the source audio signal (ds/ia), a response of the adaptive noise cancellation system to minimize the ambient audio sounds at the acoustic output of the transducer (SPKR), wherein the adaptive noise cancellation system is configured to: adapt both in the presence and the absence of the source audio signal (ds/ia); characterized in that the adaptive noise cancellation system is further configured to: enable and disable adapting the response of the adaptive noise cancellation system in the presence of the source audio signal (ds/ia) based on at least one of a persistence of the source audio signal (ds/ia) and a spectral density of the source audio signal (ds/ia), wherein a persistence of the source audio signal means that during a particular time interval, the source audio signal is substantially non-zero for at least a minimum portion of such time interval. an output configured for providing an output signal to a transducer (SPKR) including both a source audio signal (ds/ia) for playback to a listener and an anti-noise signal for countering the effect of ambient audio sounds in an acoustic output of the transducer (SPKR); and a processing circuit configured for implementing an adaptive noise cancellation system configured for generating the anti-noise signal to reduce the presence of the ambient audio sounds heard by the listener by adapting, based on a presence of the source audio signal (ds/ia), a response of the adaptive noise cancellation system to minimize the ambient audio sounds at the acoustic output of the transducer (SPKR), wherein the adaptive noise cancellation system is configured to: adapt both in the presence and the absence of the source audio signal (ds/ia); characterized in that the adaptive noise cancellation system is further configured to: enable and disable adapting the response of the adaptive noise cancellation system in the presence of the source audio signal (ds/ia) based on at least one of a persistence of the source audio signal (ds/ia) and a spectral density of the source audio signal (ds/ia), wherein a persistence of the source audio signal means that during a particular time interval, the source audio signal is substantially non-zero for at least a minimum portion of such time interval. adapt both in the presence and the absence of the source audio signal (ds/ia); characterized in that the adaptive noise cancellation system is further configured to: enable and disable adapting the response of the adaptive noise cancellation system in the presence of the source audio signal (ds/ia) based on at least one of a persistence of the source audio signal (ds/ia) and a spectral density of the source audio signal (ds/ia), wherein a persistence of the source audio signal means that during a particular time interval, the source audio signal is substantially non-zero for at least a minimum portion of such time interval.