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Noise And Crackling During A Call


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#1 Sebastian 01 September 2015 - 07:45 PM

Hi,

 

for several days we have problem with noise and crackling during a call. The problem was reported to operator but not found a problem on their side. Attached You will find a call recording and VG logs. The called number is: 666600608. Please verify whether the problem is not on the side of the VG.



#2 SupportTeam 01 September 2015 - 09:56 PM

The attached ktTel trace is for the day of 28th August, while the attached vgEngine trace is for 31st August (10:26AM to 10:40AM), and it looks like the recording was made on the 1st September at 9:09AM.

 

So looks like the attached traces are not for the time when the call recording was made.

 

Also, the attached traces do not capture any calls made to 666600608, but there are two outgoing calls where the CallerID was set to 666600608. (at 10:33:28.272 and 19:12:41.159 on 28th August)

 

 

This is a 60 port system that uses two E1 ISDN trunks.

 

E1 ISDN trunks are digital trunks. This means that the sound data sent out of the system over digital E1 channel will be byte-for-byte exactly the same as the contents of the sound file played if A-Law file is played, or will be converted to A-Law format on the Dialogic card itself if another sound file format is used.

The sound files played to callers by this system are all PCM 8kHz 16bit  format, which the Dialogic card can convert with no problems to ALaw before sending the data out over the E1 channel.

 

 

Listening to the provided recording, the crackling and faint volume is something that is typical of a poor analog connection somewhere along the path between the IVR and the call recipient. Such distortions do not occur on Digital systems, so such distortion would not be in the sound data that is played over the E1 by the Dialogic card.

 

 

This system on 28th August received 3654 incoming calls (all on the '1st' E1) and connected 1355 outgoing calls that were answered by call recipients. (all on the '2nd' E1).

Were all the calls affected by this problem?

 

Suggest to test by calling to/from various telephone numbers on different telecom networks, including numbers on the same providers network that has supplied the E1 trunks. This should help narrow down where the problem is occurring.



#3 Sebastian 02 September 2015 - 12:22 AM

Attached You will find rigth vg logs file.

 

We found similar kind of noises in case when in one prompt module in window "Sound file to play" are two files with diferent bitrate. First file is playing properly and second one with noises. Maybe something played before recording disturbing recording process.



#4 SupportTeam 02 September 2015 - 06:53 AM

Attached vgEngine trace is from 28th August (10:23AM to 10:41AM) and has one incoming call from 666600608 (at 10:33:26) and one outgoing call transfer where the outgoing call leg's CallerID was set to 666600608.

 

The recording provided earlier looks to have been made on 1st September at 9:09AM.

 

We found similar kind of noises in case when in one prompt module in window "Sound file to play" are two files with diferent bitrate. First file is playing properly and second one with noises. Maybe something played before recording disturbing recording process.

 

The bitrate mismatch problem sounds different then what was in the recorded file.

In the recorded file the played sound can be heard, and words can be be distinguished as being played at correct speed - so the problem here is not a bitrate mismatch problem.

 

The recorded file captures the faint playback and loud 'crackling' which  - as stated before - is typical of a poor analog connection somewhere along the path between the IVR and the call recipient. Such distortions do not occur on Digital systems, so such distortion would not be in the sound data that is played over the E1 by the Dialogic card.

 

It looks like this is not a problem that is not occurring on all the calls over a particular the E1 Trunk, so the advice would still be to test by calling to/from various telephone numbers on different telecom networks, including numbers on the same providers network that has supplied the E1 trunks. This should help narrow down where the problem is occurring.