Adaptive noise canceller

An adaptive noise canceler for using a secondary audio signal to remove noise from a primary audio signal, comprising:

• a first A/D converter for converting said primary audio signal to a primary digital input signal;
• a second A/D converter for converting said secondary audio signal to a secondary digital input signal;
• an adder coupled to said first A/D converter, for subtracting an estimated noise signal from said primary digital input signal to produce an error signal;
• a D/A converter coupled to said adder, for converting said error signal to an audio output signal;
• an adaptive filter coupled to said second A/D converter, for convolving said secondary digital input signal with a set of coefficients to generate said estimated noise signal, and updating said coefficients responsive to said error signal;
• and
• a power monitoring circuit coupled to said adder, for monitoring a power level of said error signal, and commanding said adaptive filter to update said coefficients according to said error signal when said power level does not exceed a threshold which is updated according to said power level, and commanding said adaptive filter not to update said coefficients when said power level exceeds said threshold.

A method of using a secondary audio signal to cancel noise in a primary audio signal, comprising:

• filtering said secondary audio signal according to a set of coefficients, thereby generating an estimated noise signal;
• subtracting said estimated noise signal from said primary audio signal to generate an error signal for use as an audio output signal;
• monitoring a power level of said primary audio signal to generate a control signal;
• when said power level exceeds a threshold which is updated according to said power level, making said control signal active to hold said coefficients constant;
• and
• when said power level does not exceed said threshold, making said control signal inactive to update said coefficients according to said error signal.

A method of using a secondary audio signal to cancel noise in a primary audio signal, comprising:

• filtering said secondary audio signal according to a set of coefficient, thereby generating an estimated noise signal;
• subtracting said estimated noise signal from said primary audio signal to generate an error signal for use as an audio output signal;
• monitoring a power level of said secondary audio signal to generate a control signal;
• when said power level does not exceed a threshold which is updated according to said power level, making said control signal active to hold said coefficients constant;
• and
• when said power level exceeds said threshold, making said control signal inactive to update said coefficients according to said error signal.

An adaptive noise canceler for using a secondary audio signal to remove noise from a primary audio signal, comprising:

• a first A/D converter for converting said primary audio signal to a primary digital input signal;
• a second A/D converter for converting said secondary audio signal to a secondary digital input signal;
• an adder coupled to said first A/D converter, for subtracting an estimated noise signal from said primary digital input signal to produce an error signal;
• a D/A converter coupled to said adder, for converting said error signal to an audio output signal;
• an adaptive filter coupled to said second A/D converter, for convolving said secondary digital input signal with a set of coefficients to generate said estimated noise signal and updating said coefficients responsive to said error signal;
• and
• a power monitoring circuit coupled to said first A/D converter, for monitoring a power level of said primary digital input signal, commanding said adaptive filter to update said coefficients according to said error signal when said power level does not exceed a threshold which is updated according to said power level, and commanding said adaptive filter not to update said coefficients when said power level exceeds said threshold.

An adaptive noise canceler for using a secondary audio signal to remove noise from a primary audio signal, comprising:

• a first A/D converter for converting said primary audio signal to a primary digital input signal;
• a second A/D converter for converting said secondary audio signal to a secondary digital input signal;
• an adder coupled to said first A/D converter, for subtracting an estimated noise signal from said primary digital input signal to produce an error signal;
• a D/A converter coupled to said adder, for converting said error signal to an audio output signal;
• an adaptive filter coupled to said second A/D converter, for convolving said secondary digital input signal with a set of coefficients to generate said estimated noise signal, and updating said coefficients responsive to said error signal;
• and
• a power monitoring circuit coupled to said second A/D converter, for monitoring a power level of said secondary digital input signal, commanding said adaptive filter to update said coefficients according to said error signal when said power level does not exceed a threshold which is updated according to said power level, and commanding said adaptive filter not to update said coefficients when said power level exceeds said threshold.