Results of modifying Input Gain, Output Attenuation

We are trying to fine-tune our voice port to minimize echo. Cisco techs have been working with us, but it seems to come down to trial and error. We have a Cisco 2851 router running CME (CallManager Express).

These are settings we have tried and the results. Any audio engineers out there care to venture a suggestion? Thank you.

Input Gain Output Attenuation Result

-3......................3.....................Echo, loud and delayed

-4......................4.....................Improved, some echo

-5..................... 6.....................Worse, more echo

-4......................5.....................Improved, still some echo

Current Voice Port Echo settings:

In Gain is Set to -4 dB Out Attenuation is Set to 5 dB Echo Cancellation is enabled Echo Cancellation NLP mute is disabled Echo Cancellation NLP threshold is -21 dB Echo Cancel Coverage is set to 64 ms Echo Cancel worst case ERL is set to 6 dB

TexasMirty, You started out with 0 db attenuation on the output side in your first posting (subj. hdr: Voice Port echo 5/2/06). You're actually adding a lot of gain by setting it to +5db. I'd kick that back down to 0db. Keep the input gain at -3db for now.

Tell us a little about how the call gets to the destinations experiencing these calls. Are these over an IXC (LD carrier)? If you're still having problems with the -3 in, 0 out, then I'd start looking elsewhere as a source of trouble. For example, are these leased-lines (T-1s) that were ordered-up between distant offices? They may have been ordered w/o echo cancellation treatment, for example. If you're running both data and voice like on a West to East Coast PRI or T-1, then you'd have to understand how it's provisioned from the carrier. Zeng