I have a few customers saying they are hearing their own voices echo back to them while they are on an off-net call. The person they are speaking with is also hearing the echo. Below, is the voice-port configuration off the gateway.
Here is how db volume works on Input gain and Output Attenuation.
Input Gain - Negative values decrease the volume from the gateway to the IP network. Positive increase the volume. Using a negative value in the Input gain decreases the volume so the echo can get serviced by the echo cancellator.
Output Attenuation - Negative values increase the volume out to the PSTN, thus increasing the chance the Echo Cancellator won't be able adjust the call if echo occurs. Positive values decrease the volume , this is usually what you do to fix the echo.
With tweaking any of these commands you can introduce a low volume problem so you really need to tweak this in small intervals or recreate the call and diagnose with the Sh call active voice so you can get an accurate level.
Greg is correct in his above statements. Three other things.
1. If the other end is hearing echo that is their own voice, then the issue is with their gateway. If they are hearing one of your users echoing then its acoustic echo and is related to the environment or your phone endpoint equipment.
2. Learn and understand the Show Call Active voice command as it will help you adjust your volumes to your desired ACOM. Here is another article just on the sh call active voice. It's probably the best overall troubleshooting command for voice gateway calls.
3. Lastly if you are using a later IOS you can set your echo-cancel coverage to the max setting. I think this was recommended from mid 12.3 and above. This is now the Cisco recommendation and the newer IOS (like 12.4) automatically defaults to the highest which in most platforms is 64ms but some due 128ms. (Traditional PBXs have been doing 128ms for awhile and about time Cisco is catching up).
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