Patent ID: 8908877

Claim:
A personal audio device, comprising: a personal audio device housing; a transducer mounted on the housing for reproducing an audio signal 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; a reference microphone mounted on the housing for providing a reference microphone signal indicative of the ambient audio sounds; an error microphone mounted on the housing in proximity to the transducer for providing an error microphone signal indicative of the acoustic output of the transducer; and a processing circuit that implements a first adaptive filter having a response that shapes the anti-noise signal to reduce the presence of the ambient audio sounds heard by the listener, wherein the first adaptive filter filters the reference microphone signal to generate the anti-noise signal, wherein the processing circuit implements a secondary path adaptive filter having a secondary path response that shapes the source audio and a combiner that removes the shaped source audio from the error microphone signal to provide an error signal indicative of the combined anti-noise signal and ambient audio sounds delivered to the listener, wherein the processing circuit adapts the response of the first adaptive filter to minimize the error signal, wherein the processing circuit determines a degree of coupling between the transducer and an ear of the listener and detects a change in the degree of coupling by comparing a value of an ear pressure indication computed from the secondary path response to a predetermined threshold, and wherein the processing circuit alters the response of the first adaptive filter in response to the value of the ear pressure indication crossing the predetermined threshold.