The conceptual key to this invention is that the signals received at two closely spaced microphones in a multipath acoustic environment are each made up of a sum of echoes of the signal received at the other one. This leads to the conclusion that the difference between the two microphone signals is a sum of echoes of the acoustic source in the environment. In the absence of a speech source, the ANS scheme proposed by Jaber first attempts to isolate the difference signal at each of the microphones by subtracting from it an adaptively predicted version of the other microphone signal. It then attempts to adaptively cancel the two difference signals. When speech is present (as detected by some type of vocoder-based strategy), the adaptive cancellation stage has its adaptivity turned off (i.e. the impulse responses of the two FIR filters, one for each microphone, are unchanged for the duration of the speech). The effect here is that the adaptive canceller does not end up cancelling the speech signal contained in the difference between the two microphone signals.

"NOISE SUPPRESSION SYSTEM WITH DUAL MICROPHONE ECHO CANCELLATION", US patent No. US 6,738,482 B1.

Accoustic Noise Supressor

To learn more about our Advanced Digital Noise Suprression Technology, you can visit our ADNST departement.

Advanced Digital Noise Suppression Technology

www.adnst.com

______________________________________________________________________________________________________________________