Systems and methods for adaptive noise cancellation by adaptively shaping internal white noise to train a secondary path

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, from the reference microphone signal, countering the effects of ambient audio sounds at an acoustic output of the transducer by adapting a response of an adaptive filter that filters an output of the reference microphone to minimize the ambient audio sounds in the error microphone signal;
• adaptively generating a secondary path estimate, from the source audio signal, by filtering the source audio signal with a secondary path estimate adaptive filter configured to model an electro-acoustic path of the source audio signal and adapting the response of the secondary path estimate adaptive filter to minimize a playback corrected error, wherein the playback corrected error is based on a difference between the error microphone signal and the secondary path estimate;
• injecting a noise signal into the source audio signal with a noise injection portion, wherein the noise signal is generated by filtering an output of a noise source with a frequency shaping filter in conformity with the playback corrected error and filtering the noise signal in conformity with at least one parameter of the secondary path estimate filter by filtering the noise signal with a response that is an inverse of at least a portion of the response of the secondary path estimate filter in order to reduce audibility of the noise signal in the audio signal reproduced by the transducer;
• and
• combining the anti-noise signal with the 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 comprising:
• an adaptive filter having a response that generates an anti-noise signal from the reference microphone signal, wherein the response is shaped in conformity with the reference microphone signal and a playback corrected error, and wherein the playback corrected error is based on a difference between the error microphone signal and a secondary path estimate;
• a secondary path estimate filter configured to model an electro-acoustic path of the source audio signal and have a response that generates the secondary path estimate from the source audio signal;
• a secondary coefficient control block that shapes the response of the secondary path estimate filter in conformity with the source audio signal and the playback corrected error by adapting the response of the secondary path estimate filter to minimize the playback corrected error;
• and
• a noise injection portion for injecting a noise signal into the source audio signal, wherein the noise signal is shaped based on the playback corrected error, wherein the noise injection portion comprises:
• a noise source;
• a frequency shaping filter having a response that generates the noise signal from the noise source and shapes the noise signal in conformity with the playback corrected error;
• and
• a filter that shapes the noise signal in conformity with at least one parameter of the secondary path estimate filter in order to reduce audibility of the noise signal in the audio signal reproduced by the transducer;
• and
• wherein a response of the noise injection portion includes a response that is an inverse of at least a portion of the response of the secondary path estimate filter.