Local echo problem

One of our customers is complaining about echo in his phones.He can hear himself talk from time to time. It can happen mutliple times during a single conversation.

After recording the calls from FreePBX and doing some packet captures, we concluded that there was absolutely no echo on the FreePBX audio. Everything is perfect in the recordings, so it’s not a case of echo coming back from the person at the other end of the line.

It looks like the echo happens locally on the phone and never reaches FreePBX. The setup is 100% VOIP, no gateway or analog lines. Happens with a Mitel and a Yealink phone.

What can cause local echo on a phone headset ? Magnetic field ? Interference ? I mean, if it was related to the trunk or the other person on the line, we would hear it in the recordings or captures right ?

One thing I did not check: test with an internal call between 2 phones.

Local echo on an analog system would be caused by all of these things.

Places (with VOIP) to look are possible network loops (the switch plugged into itself) or possibly the phone itself. Since you are hearing it with two different phones, I’d lean toward a network issue, a local LAN wiring issue, or some other “largely local” but repeatable situation like that.

Check the cabling for mouse engineering or tight corners with a cable.

You might also check the local network for things like intermittent lag or something else that might trigger the jitter buffering. If your network got laggy for a few seconds, it could cause this, and the remote end wouldn’t hear it (since the traffic is automatically deduped by the IP connection).

Thanks for the quick reply.

Intermittent lag triggering the jitter buffer looks like a good lead. I’ll will spend some time on site to test the network and cabling.

see if it occurs on all calls or just some. if just some of the calls, then tell the person reporting the issue to ask if the caller is using a headset and if yes, ask the caller to use the handset and see if the problem goes away.

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If this was the case, wouldn’t I hear the echo in the call recording ?

don’t know

If the echo is coming from the remote system, it would make sense that it would show up in the recording. Not saying it absolutely will, but it doesn’t violate the Rule of Least Astonishment.

If you are truly only hearing it on the phones and it never happens in the recordings, it has to be something external-ish to the PBX server. Long ping times, network loops, and other physical network issues are (my guess) likely culprits.

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