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.....................Impro ved, some echo
-5..................... 6.....................Worse, more echo
-4......................5.....................Impro ved, 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@gmail.com

On 18 May 2006 08:43:11 -0700, ""
<> wrote:

>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.....................Impro ved, some echo
>-5..................... 6.....................Worse, more echo
>-4......................5.....................Impro ved, 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