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Community Member

No comfort Noise

I have a phone that is not having comfort noise on it most calls. I am looking for some pointers in troubleshooting it since comfort noise is turned on and should be working. Thank you in advance for the help.

Community Member

Re: No comfort Noise


I think I understand what you want as long as comfort noise is the two beeps you can hear when on hold. Two things jump to mind. Codec issue if across a wan connection. The default codec for MOH is g711. A remote region could be set to g729. Then you would just get silence.

You may also have multi-cast and uni-cast issues. Check your settings on the source and MOH server. Try to reset the MOH servers.


Community Member

Re: No comfort Noise

Actually comfort noise is the white noise generated by an endpoint to suppress the complete silence inherent in a digital system. The analog systems all have some form of this white noise due to wiring and static. In our digital world we have to generate this noise to "trick" the user into not thinking his call had been dropped due to lack of sound. I have silence suppression turned on in callmanager but when I do a Show mgcp on the router I see that it is disabled. this seemed wierd to me and I thought it might help in troubleshooting the problem. I have just ordered troubleshooting Cisco IP Telephony since the TAC says this is their goto book. I do want to thank you you solved another problem I was having with remote sites and MOH and did not realize that it was a real problem. Thank you again

Cisco Employee

Re: No comfort Noise

You may want to check "show call active voice" on the MGCP GW. You should see VAD being enable. If its not then you also want to find out if the config it being download from CCM or being used on the GW. Just to get clarification have you tested background noise with silience supression disable on the CCM ? Last you can manually set the VAD to be enable on MGCP gateway by "mgcp vad" in config mode.

Hope that helps..



Community Member

Re: No comfort Noise

If VAD is disabled, Will comfort noise be generated?

If not, is the only way to enable it by turning on VAD?



Community Member

Re: No comfort Noise

Nope. This was fixed by turning of comfort noise and VAD. I have high bandwidth links and did not need to have silence suppression on. I was under the mis imppression that silence suppression stop the silence on a phone when actually it stops transmitting packet when the user is quiet, this actually causes the silence. Stupid problem and thank you for the help

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