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Annoying background noise on call via Trunk Voip


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I hear an annoying noise in the background on call via Trunk Voip.
I dial the external number, press send and there is this noise, then it disappears to the answer of the called.
The problem is definitely caused by the Vodia server because the same IP phone and the same network infrastructure with other Voip server the problem does not arise, how can I solve it?
Thank you

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This is the same for me. WIth Snom phone when you dial a call during invite session or 100 or 180 answers, before the UDP session start, there's a loud white noise. This noise is introduced, in some way by PBX. 

It's not a confort noise function because this should be activated only after the session RTP start. Snom, in any case send only mute RTP packet in order to maintain up the UDP session.

I Check in the phone settings of the provisioned phone and there are no option that ca be cause this behavior.

I ask because the noise is very high and leads the user to think that there is a system malfunction.

Obviously this noise completely disappears when the RTP audio session is started: at this point the audio is perfect.

This is absolutely independent from the phone or the SIP trunk.


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Well, this is called "comfort noise" (see e.g. https://en.wikipedia.org/wiki/Comfort_noise). The story goes back to the introduction of ISDN where users were confused by the digital silence they thought the system was dead and hung up while the call establishment was still in progress. This can be something like 10 seconds for example when calling  a mobile phone or even longer if your SIP trunk provider has to first hack a system to route this call to Cuba. Remember, ringback means that the other end really rings - on other words there is a human that is getting alerted. So there are two phased when calling a person - the network is trying to locate the device and the person is being alerted.

How long the comfort noise should be is of course debatable. In loud environments you want it louder , in quiet environments you want it less loud. If you want to experiment with it, the file is in audio_moh/noise.wav - if you like you can make it digital silence like in the beginning of the ISDN age or tone it down, or even make it an advertisement for your stellar hosted PBX service.

If it is a very loud ear deafening noise that does not change after connecting the call you might have a old firmware version on your phone that does not device SRTP properly. In that case the phone would receive SRTP packets but play them back as regular RTP packets.

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absolutely not, "deleting" the file noise.wav the noise disappears completely, I replaced that file with another mute with the same name and now the audio is perfect.
Can I also completely delete the noise.wav file or better if there is (even if with other audio)?




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