<br><font size=2><tt>Eecho cancellation is used to eliminate the echo which
mixed with near end speech, while it was occured by far end speech.</tt></font>
<br><font size=2><tt>It always work like this:</tt></font>
<br><font size=2><tt>Find the similar speech in near end speech and eliminate
it.</tt></font>
<br>
<br><font size=2><tt>In case 1:</tt></font>
<br><font size=2><tt>Because the there is no echo in near end speech, and
the EC module still works on it. So a inverse model is been calculated,
and a inverse signal is produced. In this way , you can hear the far end
speech.</tt></font>
<br>
<br><font size=2><tt>In case 2:</tt></font>
<br><font size=2><tt>Is the NES is produeced by FES? </tt></font>
<br><font size=2><tt>Maybe EC can not recognise the speech as human been
just because it is similar.</tt></font>
<br>
<br>
<br><font size=2 face="sans-serif">If you want to check the EC, I think
you should prepare a echo path model (you can find some typical models
on G.168 ). You get a echo signal when the model applied on FES.</font>
<br>
<br><font size=2 face="sans-serif">Once you want a signle talk test, you
can use the echo signal as the NES.</font>
<br>
<br><font size=2 face="sans-serif">If you want to test double talk, you
can add the echo signal with another speech.</font>
<br>
<br>
<br><font size=2 face="sans-serif"><br>
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