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Discussion Groups | Echo Cancellation | noise suppression + echo cancellation
noise suppression + echo cancellation - Mukul Bhatnagar - Sep 30 23:48:00 2002
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Hi All I had another question, in order to make an echo cancellers performance more robust in noise, if we integrate it with a noise suppression algorithm- for instance Spectral Subtraction. What is more advisable "theoritically" 1) To put the Noise suppression algorithm before the AEC so that the near end input to AEC is more cleaner- reducing the possibility of divergence. 2) Or put it after the AEC, whereby , since the noise suppression filter will probably have time varying characteristics, would probably have to be accounted for in the echo path for the echo canceller? TIA Mukul PS>I am aware of some proposals that provide integrated solutions, but wanted to know , how the problem could be solved treating two individual solutions as two separate blocks! |
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RE: noise suppression + echo cancellation - Shaw, David G David - Oct 1 12:41:00 2002
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Mukul wrote: What is more advisable "theoritically" 1) To put the Noise suppression algorithm before the AEC so that the near end input to AEC is more cleaner- reducing the possibility of divergence. (DGS) I believe you would do irreparable damage to the signal, since spectral subtraction is clearly a very non-linear process. I think your ability to converge a canceller would be compromised substantially. 2) Or put it after the AEC, whereby , since the noise suppression filter will probably have time varying characteristics, would probably have to be accounted for in the echo path for the echo canceller? (DGS) Use the noise suppression as a clean up of all the residual that you can't get rid of with cancellation. You will have to do some clean up after the acoustic canceller anyway. TIA Mukul (DGS) Regards Dave Shaw |
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Re: noise suppression + echo cancellation - Author Unknown - Oct 1 12:48:00 2002
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Hi Mukul, Noise reduction before AEC appears to me as the worst solution since you lose any hope of having a linear relation between the far end signal and the echo enhanced by your spectral substraction. LMS and RLS rely on that crucial linear relation. In case of LMS, you'd better use a variable adaptation step size to avoid divergence in presence of noise. As far as I know, integrated solutions only deal with reducing the residual echo thanks to noise reduction techniques. regards, David Mukul Bhatnagar <> 01/10/02 01:48 Please respond to echocancel To: cc: Subject: [echocancel] noise suppression + echo cancellation Hi All I had another question, in order to make an echo cancellers performance more robust in noise, if we integrate it with a noise suppression algorithm- for instance Spectral Subtraction. What is more advisable "theoritically" 1) To put the Noise suppression algorithm before the AEC so that the near end input to AEC is more cleaner- reducing the possibility of divergence. 2) Or put it after the AEC, whereby , since the noise suppression filter will probably have time varying characteristics, would probably have to be accounted for in the echo path for the echo canceller? TIA Mukul PS>I am aware of some proposals that provide integrated solutions, but wanted to know , how the problem could be solved treating two individual solutions as two separate blocks! _____________________________________ |
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