Choppy lines on server behind firewall

Good day,
We recently move our PBX Server behind firewall thats the time we encountered choppy lines. Is the firewall something to do with this?

Asterisk 1.4.21.2

Help will be much appreciated.

G-rom

If your change in call quality coincided with the relocation of the server behind the firewall, then the firewall is the likely cause of your troubles. Place priority on SIP and RTP traffic in your firewall to prevent loss of audio quality due to saturation at your router.

Good luck.