Systems and methods for adaptive noise cancellation including secondary path estimate monitoring

A method for canceling ambient audio sounds in the proximity of a transducer of a personal audio device, the method comprising:

• receiving a reference microphone signal indicative of the ambient audio sounds;
• receiving an error microphone signal indicative of the output of the transducer and the ambient audio sounds at the transducer;
• generating a source audio signal for playback to a listener;
• generating an anti-noise signal for countering the effects of ambient audio sounds at an acoustic output of the transducer;
• generating a secondary path estimate from the source audio signal by filtering the source audio signal with a secondary path estimate filter modeling an electro-acoustic path of the source audio signal;
• monitoring with a secondary path estimate performance monitor performance of the secondary path estimate filter in modeling the electro-acoustic path based on the error microphone signal and a playback correct error signal, wherein the playback corrected error is based on a difference between the error microphone signal and the secondary path estimate;
• and
• combining the anti-noise signal with a source audio signal to generate an audio signal provided to the transducer.

An integrated circuit for implementing at least a portion of a personal audio device, comprising:

• an output for providing a signal to a transducer including both a source audio signal 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;
• a reference microphone input for receiving a reference microphone signal indicative of the ambient audio sounds;
• an error microphone input for receiving an error microphone signal indicative of the output of the transducer and the ambient audio sounds at the transducer;
• and
• a processing circuit that implements:
• an anti-noise generating filter having a response that generates at least a portion of the anti-noise signal;
• a secondary path estimate filter configured to model an electro-acoustic path of the source audio signal and have a response that generates a secondary path estimate from the source audio signal;
• and
• a secondary path estimate performance monitor for monitoring performance of the secondary path estimate filter in modeling the electro-acoustic path based on the error microphone signal and a playback correct error signal, wherein the playback corrected error is based on a difference between the error microphone signal and the secondary path estimate.