Hi…i have this problem…when i call out or i receive an external call i have a big noise in background…This noise there isn’t if i call an internal phone…
What i can do??? Is a problem on isdn card?? 
Thanks 
Are you using a Digium ISDN card?
No…i use OpenVox B100P ISDN BRI Card, with Dahdi…
I changed the pbx, on the old pbx the ISDN card worked well, but on the new pbx there is this proplem of the noise in background 
…help me…
Sorry. Contact your vendor. If they’re selling cards, they should be providing support.
Did you change machines or only the PBX software ?
yes…but i don’t know why before the card didn’t have this problem…i change the pc, version of Asterisk.
I have change machines and pbx software…before there was asterisk 1.4 and now 1.8…before mISDN and now Dahdi…1 week ago there wasn’t this problem on the new pbx, i only restart some times the pc…and now i have this problem
Perhaps something happened to the card itself. Do you have any diagnostic tool to test the card itself ? Maybe you got one when you purchased the cards or maybe you can find some diagnostic tool on your vendor’s web site.
I’ve seen this issue before on Mitel PBXs (once in a blue moon), normally its cleared if the unit is simply rebooted.
Otherwise you may have to call your service provider for your BRI and get them to put your BRI in loopback and test.
Though, I would imagine that it would be easiest to just contact your card vendor first.