Abnormal DTMF tone

[engineerauob]

Dears,

            I have a SIP trunk with one of my customers and he is complaining of hearing abnormal DTMF tones during the call. Does anyone have an idea what the problem might be.

[Jonathan Schulenberg]

Is the customer hearing the abnormal tone when they press a DTMF button; or, when the far-end presses a button which they then hear?

If your customer is pressing the button, ensure that the phone's Network Locale is what you expect.

If the far-end presses the button the first question is whether it's being recognized as an actual DTMF event or just random in-band audio. Assuming your SIP trunk uses RFC2833 you can run debug voip rtp session named-event and see whether when they press the button, does the carrier send you NTE? If not, then it's just audio on the call and you can try opening a ticket with the carrier.

[engineerauob]

Thanks Jonathan for your prompt response. but the issue is that neither the caller or the called are pressing any button but still hearing this DTMF tones whenever the caller starts to speaks. 

[Jonathan Schulenberg]

I suggest getting a packet capture of the call from the CUBE-to-ITSP side and opening a ticket with the vendor then. Play it back in Wireshark and ensure that you can hear the tones within the received RTP stream.

[kdotten36]

This isn't the oldest thread I've ever dug back up, but did you find out what was causing this?  Happening for me too on a SIP trunk from CUCM 9.1 > CUBE 15 > ITSP