5.1 Surround set doing weird

Hello all!

I've got a 5.1 surround set (logitech X-530) which works pretty good but sometimes it suddenly produces a loud bang.
It happens when they are on and i for example turn the lights on, but also when i'm just playing a game or listening to music. (happens like 1-10 times a day)

But in the last few weeks I noticed another thing which is quite scary.
Sometimes it sounds like people are talking while I don't have any music or video(game) on but when I turn down the volume a bit the talking actually becomes louder, except when I fully turn it down.
When I listen carefully, the voices sound French and it's like a radio station or something.
This is really creeping me out. xD

Anyone got a solution or has the same problem?