Sound and speech came back into headphones with eco

Hi guys, I have a big problem.

I am using TS3 Client (3.0.13.1 QT: 4.8.3) and until now I hadn't had any problem. Now when we connect my friends say that they hear an eco that came back into the headphones. I have tried many setting to solve this matter but I realy don't know what can I do.
All my friends have the new version of TS, but the server where we connect is older than mine and, as I've said upon, until some days ago I have never had any noise or problems.
Have you any suggestions?

Thanks

Paolo

Sound and speech came back into headphones with eco