Firstly I’m a noob so please go easy on me.
I’ve just installed ‘FreePBX-Distro-Net-’ for the 3rd time, the first 2 times I installed on a virtual machine in hyper-V but I had a bad crackling sound when I made internal calls, so I’ve installed on a standalone machine but I have exactly the same problem.

I’m using a Linksys pap2 device, and 3CX sofware on my android phone (Nexus S).

So far thats all I have, just 2 extensions, no trunks or anything.

If I put either extension on hold, then the music is as clear as a bell, but a voice call is really noisy.

It also crackles when I do an echo test.

I tried altering the mic gain in the 3CX software but it made no difference.
The crackle is instant, as soon as the call connects.

Any suggestions appreciated.


I suspect the problem is related to the 3CX software on your android phone. Does the problem occur when you make a call without include your android phone?

Try another VOIP client. There are lots of free Android clients, and some good paid ones too.

The crackling sound is due to a ~bad~ audio implementation (not standard Android) from the manufacturer. We had the same issue with csipsimple (more here).

I would try Bria (the best SIP software). I think you have to use “speakerphone fix” and turn off QOS or some other option. Just play with the settings and you’ll get rid of the crackling sound. 3CX is nothing special. The Original software was called SipAgent (very promising) but it was sold to 3CX and they did not do much with it.

I’ve read good things about Bria as well, but haven’t had time to try it.

I know its been a long time, but I thought I’d update this thread just in case anyone else is interested.
It turned out it was the pap2 device that was at fault.

I replaced it with a grandstream handset, and everything is crystal clear again.

Thanks for the comments/suggestions.