Choppy audio at the start of each word in a conversation

[isdn3cxuser]

We have a 3CX box that has just been installed that is having issues with external calls over ISDN30. Basically when people talk is seems to cut off the first bit of the word when they start talking. An example is below:

http://213.229.67.234/20111103120352.wav

It happens 5 times in this short clip, I can't really describe it, it's best to listen for yourselves. Internal calls are fine, it's just calls over the ISDN30. What could be causing this?

All phones are Snom 821s with the latest firmware. The 3CX software is running on a new HP ML110G6 server with Windows Foundation Server 2008. It has dual SSDs and uses a Sangoma A101 PCI-E card for the ISDN30. The logs for 3CX and the Sangoma show nothing and the phone company have tested the ISDN line and say it's fine.

 

[A.burton]

I not sure if this helps but I had a very similar problem on an SPA3102 box attached to 3cx. I was able to fix the problem by tweaking a few settings. I changed the echo cancellation settings, the network jitter level from high to low (after doing a test to determine lost packets =0) and I also changed a setting for the comfort noise generater. The CNG is a way of saving bandwidth by not transmitting packets during silence. Maybe you have similar settings on your ISDN box.