FreePBX/Sangoma Call Noise Cancelling

We are currently using a mix of Sangoma P325 & 330s, connecting to a FreePBX Appliance and a Vega 60 v2 Gateway for POTS lines. When making/receiving phone calls, users are reporting they are unable to hear the person on the remote end while they are speaking but as soon as they stop talking, you can hear the other person again almost like somewhere in the system there is some kind of noise cancelling happening. Is there any specific settings I should be looking at to correct this?

There should be echo suppression (not noise cancellation) in both the phones and the PSTN gateway. The simplest form of echo suppression is to mute the line in the reverse direction. This is often used in loud speaking phones, as the echo environment can be complex. The other approach is an adaptive canceller, which learns the echo characteristics, but that needs to be trained, and will not respond quickly to sudden changes in the echo characteristics.

Without echo suppression, the time delays introduced by VoIP mean that the echo is l likely to be intolerable, so you do not want to disable this at the analogue/circuit switched boundaries. VoIP phones generally take care of their own suppression for acoustic echoes local to them, but the analogue network doesn’t do so on the other side, so the boundary system needs to handle this. In this case it will be the Vega.

I think you will need to replace the Vega with something that does adaptive cancellation, but accept that this may not handle switching transients, or speaker phones, at the far end, well.