Rejecting noise with paired microphones

An apparatus for combining signals comprising:

• a first microphone generating a first input signal having a first voice component and a first noise component;
• a second microphone generating a second input signal having a second voice component and a second noise component;
• a mixing circuit configured to:
• apply a first gain having a value α to the first input signal to produce a first scaled signal;
• apply a second gain having a value 1−α to the second input signal to produce a second scaled signal;
• and
• sum the first scaled signal and the second scaled signal to produce a summed signal;
• an adaptive filter configured to compute an updated value of α to minimize the energy of the summed signal based on the summed signal, the first input signal and the second input signal, and to provide the updated value of α to the mixing circuit;
• a first equalizer configured to apply a first equalization curve to the first input signal to produce a first equalized signal, and
• a second equalizer configured to apply a second equalization curve to the second input signal to produce a second equalized signal,
• the first and second equalized signals having matching voice components.

An apparatus for combining signals comprising:

• a first microphone generating a first input signal having a first voice component and a first noise component;
• a second microphone generating a second input signal having a second voice component and a second noise component;
• a mixing circuit configured to:
• apply a first gain having a value α to the first input signal to produce a first scaled signal;
• apply a second gain having a value 1−α to the second input signal to produce a second scaled signal;
• and
• sum the first scaled signal and the second scaled signal to produce a summed signal;
• an adaptive filter configured to compute an updated value of α to minimize the energy of the summed signal based on the summed signal, the first input signal and the second input signal, and to provide the updated value of α to the mixing circuit;
• and
• a single equalizer configured to apply an equalization curve to the first input signal to produce a first equalized signal,
• the first equalized signal having an equalized voice component matching the second voice component from the second input signal.

A method of combining signals comprising:

• receiving a first input signal from a first microphone, the first input signal having a first voice component representing the response of the first microphone to voice, and a first noise component representing the response of the first microphone to noise;
• receiving a second input signal from a second microphone, the second input signal having a second voice component representing the voice response of the second microphone, and a second noise component representing the response of the second microphone to noise;
• applying a first gain having a value α to the first input signal to produce a first scaled signal;
• applying a second gain having a value 1−α to the second input signal to produce a second scaled signal;
• summing the first scaled signal and the second scaled signal to produce a summed signal;
• in an adaptive filter, computing an updated value of α to minimize the energy of the summed signal based on the summed signal, the first input signal, and the second input signal;
• updating the values of the first and second gains based on the updated value of α;
• and
• outputting the summed signal based on the updated value of α;
• wherein computing the updated value of α comprises applying a least-mean-squared algorithm by, in a digital signal processor:
• computing a difference between the first and second signals,
• multiplying the summed signal by the difference and by a pre-determined step size value, and
• subtracting the product from the current value of α to produce the updated value of α.

A method of combining signals comprising:

• receiving a first input signal from a first microphone, the first input signal having a first voice component representing the response of the first microphone to voice, and a first noise component representing the response of the first microphone to noise;
• receiving a second input signal from a second microphone, the second input signal having a second voice component representing the voice response of the second microphone, and a second noise component representing the response of the second microphone to noise;
• applying a first gain having a value α to the first input signal to produce a first scaled signal;
• applying a second gain having a value 1−α to the second input signal to produce a second scaled signal;
• summing the first scaled signal and the second scaled signal to produce a summed signal;
• in an adaptive filter, computing an updated value of α to minimize the energy of the summed signal based on the summed signal, the first input signal, and the second input signal;
• updating the values of the first and second gains based on the updated value of α;
• and
• outputting the summed signal based on the updated value of α;
• applying a first equalization curve to the first input signal to produce a first equalized signal;
• and
• applying a second equalization curve to the second input signal to produce a second equalized signal, the first and second equalized signals having matching voice components.

A method of combining signals comprising:

• receiving a first input signal from a first microphone, the first input signal having a first voice component representing the response of the first microphone to voice, and a first noise component representing the response of the first microphone to noise;
• receiving a second input signal from a second microphone, the second input signal having a second voice component representing the voice response of the second microphone, and a second noise component representing the response of the second microphone to noise;
• applying a first gain having a value α to the first input signal to produce a first scaled signal;
• applying a second gain having a value 1−α to the second input signal to produce a second scaled signal;
• summing the first scaled signal and the second scaled signal to produce a summed signal;
• in an adaptive filter, computing an updated value of α to minimize the energy of the summed signal based on the summed signal, the first input signal, and the second input signal;
• updating the values of the first and second gains based on the updated value of α;
• and
• outputting the summed signal based on the updated value of α;
• and
• applying a first equalization curve to the first input signal to produce a first equalized signal, the first equalized signal having an equalized voice component matching the second voice component from the second input signal.