Umm, without seeing your specific system set-up, I would say you're getting some kind of RF interference in the system. Are you sure that you're hearing "TV sounds"? You may be actually hearing a local radio station coming through a long cable run.

Here's a couple of tests.

1) Turn off each piece of gear one at a time. See if you hear any changes in the "sound" as each piece goes off.

2) Unplug everything from your receiver except for your speakers. Now what do you hear? If you're still hearing something, unplug one speaker at a time until it goes away.

This is just something to start with. As I said, without knowing system specifics, it's really just guess and check. Good luck!