Muffled sound using tdm400 , analogue line and sip


I am in the process of setting up an asterisk server to replace our old norstar system. Just need to test it first before we go live with it.

It P4 2.4ghz pc with fc3 and asterisk,libpri and zaptel 1.2
I have setup 4 eyebeam ver(1.1 3004w) sip softphones on extensions.

The box is connected to a Bt Uk Analogue line using a Digium tdm400p with 1 fxo card. In the future we will get a card to link to isdn30

Everything seems to work except people who are testing is are keep
saying the voices sound muffled on outgoing and incomming calls via the bt line. Even tried it with different headsets.

Eyebeam shows gsm codec.

I have the rxgain =10.5 and txgain=4.5

What and where should I look for this problem. ?




first thing to ask is whether you’re loading your wctdm module with the right settings for UK.

next is to ask whether you are going to use only softphones ? if so, i would reconsider. even the cheapest hardphone (BT102) i think is better than a softphone.

is there a reason you’re using GSM ? you’ll get better voice quality using G711 and if it’s all LAN you should be ok.

how did you arrive at your gain settings ? what echo canceller are you using ?

the only other thing that comes to mind is whether the PCI slot you have the TDM in is rev 2.2 … horrible things happen in my experience if it’s not.


I have checked the wctdm module and it is set for uk. Shows Tone Zone 4 UK in message logs when loaded.

Also set the sip.conf to use G711 Codec.

The zaptel echo canceller is the default one installed using 1.2.1 and I have tried using ztmonitor to set the rx/tx gain so both are around the middle of the *** graph.

I cannot tel if the m/b rev 2.2 except if it a qdi p4 board.
Some people still say i sound muffled but I will test it a bit more.

Is it ok to use a standard atx psu or should we use a better quality one as the lead plugs into the tdm400p card. Would a cheap psu affect it?.



i would still suspect your softphone for poor sound quality. have you tried recording your calls to see what they sound like ? also, try being the one at the other end of the PSTN line.

in theory, a board that recent should be PCI revision 2.2 or above, but i think it pays to check.