Echo during a call

My FreePBX system has echo sounds when during a call. The echo is that I can hear myself for a split second and the other side’s call volume is lower for that same split second. I image that it would be a IP network problem. Where should I pin point in narrowing down the possible causes and to fix it?

System OS: FreePBX 16.0.33

If you make a recording from an extension, is the echo present?

Echoes on VoIP aren’t IP related. IP phones have to go out of their way to suppress echoes because the round trip time is long enough for them to be annoying.

If you are hearing the tail of your speech, both phones are probably using the same echo suppression tactic, the simpler one of trying to only send in one direction at a time. What is probably happening is that your phone is detecting that you have stopped talking and has opened up reception of the other side, but the round trip time is so large that your echo is still coming back. The remote phone has probably largely muted its own contribution, although I’m not sure why that is allowing them to generate any echo. It is possible that the more sophisticated form of echo suppression is also present and that is being confused by muting and unmuting.

The more sophisticated method is actually learn the echo characteristics of the connection and, predict the echo, and subtract it out. However it can take time to learn, and it will have to relearn if the echo characteristic change. It will take time to decide that it needs to switch from cancellation to learning.

Using a loud speaking phone at the far end is particularly likely to cause bad echo problems.

Please fully describe all the endpoints involved and the route(s) between them

Can you specify what method of recording?

I’m going to try. I hope I correctly give you what you need in your question.

My phone is a Sangoma S500. I’ve seen some Sangoma phones have an HD logo printed on the handset. Our firm’s one don’t. Our office space may have some echo because our flooring is laminate and there’s echo in the rooms.

The call is from said Sangoma S500 to an outside caller. We didn’t inquire what the other caller endpoint is (iPhone or landline phone)

The S500 is running on the latest firmware available from the EPM. Our EPM is fully licensed.

The network topology is quite standard: S500 → Unifi Switch → FreePBX → Unifi Switch → Router →

If you can hear a noticeable echo, it is almost certainly coming from the far end. It could be electrical, as well as acoustic, but even in an acoustically dead room there will be coupling between the earpiece and the microphone of the telephone, both through the air and through the structure of the phone.

You don’t notice echo on traditional, landline, phone systems, as, even a 1000km call only accumulates about 10ms round trip delay. However, delays on VoIP start at 40ms round trip, and are often much longer. VoIP systems have to take active steps to hide or remove echoes, based on imperfect information.

(I think some echo suppression may have been done within the continental US on traditional systems, but that was not the case within the UK, although it was done for transatlantic traffic.)

I think there will be significant delays between Router and, so that part of the internet is relevant. In many cases there will also be ISDN and possibly analogue or mobile air interface connections beyond Even if it stays within VoIP, there will be further internet delay sources.

Echo control measures will be applied by the VoIP phones and at all boundaries between VoIP and traditional networks, and possibly on longer parts of traditional networks. Generally they will be aimed at stopping the echo from the echo source nearest them, as that is technically easier. Your phone will be trying to stop the remote party hearing echo through your phone and should be trying to protect your from echo from legacy networks.

If you are hearing the echo, the basic fault lies somewhere between or including and the air in the room containing the other party. It is possible that your phone is muting the other party whilst you are speaking, but most unlikely that it would try to cancel their echo, as it not possible to do it well with such long round trip times as you likely have.

Like recording a voicemail greeting or make a system recording by entering an extension and record it from there.
Just to see if you are dealing with an issue with the phones working together.

I recorded two vm greetings from my own Sangoma S500 (unavailable and busy), both came out crystal clear.

These phones don’t happen to be near each other? If they are close they could be picking up audio from each other. I am not familiar with the specific phones you have, but it might be worth checking the audio settings for echo and or noise suppression.

Nope, they are in their own offices, separated by a walls.