[asterisk-users] Distorted Audio for incoming DTMF

[Brent Davidson]

Does anyone have any idea what would cause distorted audio but ONLY for 
DTMF tones coming in over our analog lines.  (The analog interfaces are 
X100P's).  I have carefully adjusted the gains in the zapata.conf using 
a local test line after trying various settings with no gain or just 
random gain settings.  RelaxDTMF has no effect.  I set up a monitor 
command in my dial plan to capture separate In and Out audio streams 
during the main menu portion of my IVR so I can listen to the tones 
being played. 

On most calls, the tones appear to be detected properly and are muted 
out of the audio stream (except for a slight click at the beginning of 
the tone).  For problem calls, the tones can be heard in the audio 
stream as terribly distorted.  sometimes the distortion is like the tone 
being echoed back over itself with some sort of pitch shift, other times 
the distortion is like the tone is being over-amplified.  The unusual 
thing is that regular audio on these calls is fine.

I'm using Asterisk 1.4.18.1, Zaptel 1.4.9.2 built with Oslec SVN running 
under Centos 5.0 (runlevel 3 to rule out interference from X Windows) on 
an AMD Athlon 64 4000 with 2 gigs ram. 

I can provide audio examples to anyone that is interested.

Thanks,
Brent Davidson