Patent ID: 7817808

Claim:
A method of improving the signal to noise ratio in a communication system, the method comprising: a) acquiring one or more buffers of sound samples from a back microphone and a front microphone, resulting in a back microphone signal and a front microphone signal; b) applying a propagation delay between the two microphones for a length of time equal to one sample, resulting in a delayed back microphone signal and a delayed front microphone signal; c) subtracting the delayed back microphone signal from the front microphone signal; d) subtracting the back microphone signal from the delayed front microphone signal; e) using a first adaptive filter, the first adaptive filter calculating weights adaptively, as the ratios of the cross-correlation between the two microphones R xy , and the auto-correlation of the back microphone, R yy , and averaging the auto-correlation and cross-correlation for smoothing purposes; f) subtracting the output of the first adaptive filter from a signal obtained by subtracting the delayed back microphone signal from the front microphone signal, giving a first level of output processing; g) using a voice activity detector to determine speech and non-speech regions and to control the first adaptive filter and a second adaptive filter; h) during non-speech regions, the voice activity detector is in an off position and weights of the second adaptive filter are updated, and the second adaptive filter receives a signal obtained by subtracting the back microphone signal from the delayed front microphone signal, the output from the second adaptive filter is sent to a second level processing unit; i) during speech regions, the voice activity detector in is an on position and freezes adaptive weight calculations and send the resulting output to the second level processing unit; and j) the second level processing unit removes residual noise left over from the first processing level.