we have build an Asterisk solution (version 18.6, PJSIP2.10 and alaw codec used) and a couple of users complain that they hear noise at some specific parts of the call flows. Other users are not able to reproduce this error.
The investigation, I did, showed that at these specific parts, silence should be heard (e.g. waiting for user input).
We have also a tcpdump wireshark log file at the time of the error, which showed that the RTP sent to core network is clear and with no noise at all. Furthermore, analysis from core network did not reveal something unusual.
Is it valid to conclude that the devices of these users could generate the noise audio under some specific circumstances (e.g. at a specific silent case)? Have you ever heard of something similar? How could we proceed with troubleshooting, in order to find the root cause of this behavior?
Thank you in advance.