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.