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I have the following diagram for acoustic echo cancellation

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I'm having a hard time figuring out what's present on the top and bottom lines in terms of reflected echos, original signal etc. Here's what I think

  • I am assuming a situation in which I am talking in my microphone at home via some software to a meeting room in which a teleconfrencing setup is present. The microphone and speaker in the diagram repersent the teleconfrencing setup. My voice goes through the teleconfrencing speakers, hit's the walls of the meeting room and back into the microphone.

So, what I think is that the right after the microphone symbol in the diagram is my echoed voice x_echo[n] On the bottom line at the speakers, only my original voice should be present since that's what's meant to be going through the speakers - so x[n]. Now, if that's the desired signal for my LMS adaptive filter, then how would my LMS adpative filter work, there would be no correlation at all.

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The acoustic echo canceler (AEC) is supposed to cancel any signal in the microphone path that is correlated to the speaker signal. The microphone doesn't only pick up your voice but it also picks up the signal from the speaker, i.e., the signal from the far end. If there were no AEC, that signal from the speaker would be fed back to the far end, which is very disturbing. Since the speaker signal is available at the near end, it can be used as the input to the adaptive filter, which tries to remove any signal in the outgoing path that is correlated with the speaker signal. Basically, the adaptive filter will converge to the room impulse response between loudspeaker and microphone.

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  • $\begingroup$ Ah that makes so much more sense. $\endgroup$ – AlfroJang80 Dec 11 '18 at 19:55

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