Systems and methods for use of adaptive secondary path estimate to control equalization in an audio device

A method comprising:

• receiving an error microphone signal indicative of an acoustic output of a transducer;
• modeling an electro-acoustical path of a source audio signal with a secondary path estimate filter;
• adapting a response of the secondary path estimate filter in conformity with the error microphone signal;
• generating an equalized source audio signal from a source audio signal by filtering the source audio signal with an adjustable equalization filter to account for effects of changes in the electro-acoustical path of the source audio signal;
• adapting a response of the adjustable equalization filter in response to changes in the response of the secondary path estimate filter to minimize a difference between the response of a target filter and the response of the adjustable equalization filter wherein the target filter has a response which is a function of the response of the secondary path estimate filter;
• and
• outputting a blended equalized source audio signal, wherein the blended equalized source audio signal is cross-faded between the source audio signal as filtered by the target filter and the source audio signal as filtered by the adjustable equalization filter.

An integrated circuit comprising:

• an output for providing a signal to a transducer including an equalized source audio signal for playback;
• an error microphone input for receiving an error microphone signal indicative of an acoustic output of the transducer;
• and
• a processing circuit that implements:
• a secondary path estimate filter for modeling an electro-acoustical path of a source audio signal through the transducer;
• a secondary path estimate filter coefficient control block that shapes a response of the secondary path estimate filter in conformity with the error microphone signal;
• an adjustable equalization filter having a response that generates the equalized source audio signal from the source audio signal to account for effects of changes in the electro-acoustical path of the source audio signal;
• an equalizer coefficient control block that adapts the response of the adjustable equalization filter in response to changes in the response of the secondary path estimate filter to shape the response of the adjustable equalization filter in conformity with a response of a target filter by adapting the response of the adjustable equalization filter to minimize a difference between the response of the target filter and the response of the adjustable equalization filter;
• and
• a mixer for outputting a blended equalized source audio signal, wherein the blended equalized source audio signal is cross-faded between the source audio signal as filtered by the target filter and the source audio signal as filtered by the adjustable equalization filter.

A personal audio device comprising:

• a personal audio device housing;
• a transducer coupled to the housing for reproducing an output audio signal including an equalized source audio signal for playback to a listener;
• an error microphone coupled to the housing in proximity to the transducer for providing an error microphone signal indicative of an acoustic output of the transducer;
• a processing circuit that implements:
• a secondary path estimate filter for modeling an electro-acoustical path of a source audio signal through the transducer;
• a secondary path estimate filter coefficient control block that shapes a response of the secondary path estimate filter in conformity with the error microphone signal;
• an adjustable equalization filter having a response that generates an equalized source audio signal from the source audio signal to account for effects of changes in the electro-acoustical path of the source audio signal;
• and
• an equalizer coefficient control block that adapts the response of the adjustable equalization filter in response to changes in the response of the secondary path estimate filter to shape the response of the adjustable equalization filter in conformity with a response of a target filter by adapting the response of the adjustable equalization filter to minimize a difference between the response of the target filter and the response of the adjustable equalization filter;
• wherein the equalizer coefficient control block is configured to shape the response of the adjustable equalization filter in conformity with the response of the target filter by adapting the response of the adjustable equalization filter to minimize a difference between the source audio signal as filtered by the target filter and the source audio signal as filtered by the adjustable equalization filter using a least-mean-squares adaptation technique.

A method comprising:

• receiving an error microphone signal indicative of an acoustic output of a transducer;
• modeling an electro-acoustical path of a source audio signal with a secondary path estimate filter;
• adapting a response of the secondary path estimate filter in conformity with the error microphone signal;
• generating an equalized source audio signal from a source audio signal by filtering the source audio signal with an adjustable equalization filter to account for effects of changes in the electro-acoustical path of the source audio signal;
• adapting a response of the adjustable equalization filter in response to changes in the response of the secondary path estimate filter to minimize a difference between the response of the target filter and the response of the adjustable equalization filter;
• and
• adapting the response of the adjustable equalization filter to minimize a difference between the source audio signal as filtered by the target filter and the source audio signal as filtered by adjustable equalization filter using a least-mean-squares adaptation technique.

An integrated circuit comprising:

• an output for providing a signal to a transducer including an equalized source audio signal for playback;
• an error microphone input for receiving an error microphone signal indicative of an acoustic output of the transducer;
• and
• a processing circuit that implements:
• a secondary path estimate filter for modeling an electro-acoustical path of a source audio signal through the transducer;
• a secondary path estimate filter coefficient control block that shapes a response of the secondary path estimate filter in conformity with the error microphone signal;
• an adjustable equalization filter having a response that generates the equalized source audio signal from the source audio signal to account for effects of changes in the electro-acoustical path of the source audio signal;
• and
• an equalizer coefficient control block that adapts the response of the adjustable equalization filter in response to changes in the response of the secondary path estimate filter to shape the response of the adjustable equalization filter in conformity with a response of a target filter by adapting the response of the adjustable equalization filter to minimize a difference between the response of the target filter and the response of the adjustable equalization filter, wherein the equalizer coefficient control block is configured to shape the response of the adjustable equalization filter in conformity with the response of the target filter by adapting the response of the adjustable equalization filter to minimize a difference between the source audio signal as filtered by the target filter and the source audio signal as filtered by the adjustable equalization filter using a least-mean-squares adaptation technique.