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New Member

Comfort Noise on H.323 Gateway

I have a 4224 with T1 CAS delivering 5 lines of digital voice. Previously was using FXO ports in same box. Since switching to digital, I have been having trouble with comfort noise. I have turned comfort noise off on voice-ports. I have turned VAD off on voip dial-peer. I have silence-suppression off systemwide and on gateways on callmanager. Callmanager 3.2 with 12.2(2)YC on 4224. Was previously using MGCP with FXO ports, other than that, no other changes made to code revisions or configuration.

voice-port 1/0:0

no comfort-noise


voice-port 1/0:1

no comfort-noise


dial-peer voice 200 voip

description ****CALLMANAGER H.323 GATEWAY****

destination-pattern 2...

session target ipv4:

dtmf-relay h245-alphanumeric

codec g711ulaw

no vad


dial-peer voice 100 pots

description ****DIGITAL LINES****

preference 1

destination-pattern 9.T

port 1/0:0


dial-peer voice 101 pots

description ****DIGITAL FAX LINE****

preference 2

destination-pattern 9.T

port 1/0:1



New Member

Re: Comfort Noise on H.323 Gateway

I ended up answering my own question, but here is the breakdown for everyone else's viewing pleasure:

1) Catalyst 4224 running IOS 12.2(2)YC and MGCP with CM 3.2(1) with Analog VIC-2FXO ports connected to PSTN. I have comfort noise and VAD disabled on 4224 and CM. I have no audio quality issues.

2) Replace VIC-2FXO ports in Catalyst 4224 with VWIC-2MFT-T1 with T1 CAS and H.323 instead of MGCP. Still IOS 12.2(2)YC and CM 3.2(1). I now hear what appears to be comfort noise or static on PSTN calls when there are gaps in outside callers speech (only appears to happen when on handset or headset, NOT speakerphone). I still have comfort noise and VAD disabled on Catalyst 4224 and CM. Shut/no Shut voice ports, reloaded router, removed config and replaced, still have "comfort" noise.

3) Without changing my software or hardware configuration, I "downgraded" IOS on Catalyst 4224 to 12.1(5)YE5 and reloaded. Voice quality is restored (no comfort noise).


"Comfort Noise" Bug in 12.2(2)YC?