Problem with LCD T.V., scratching/buzzing sound

I've had a problem with my LG 42CS560 LCD TV for a little while because of a scratching/buzzing sound during gameplay. I'm playing a PS3. The sound doesn't happen when I have the TV muted. Example of what happens in The Last of Us: whenever a loud sound happens in-game the scratching/buzz sound will happen briefly. Jumping to the ground from a ledge, gunshots, voice over in cutscenes etc. It seems to get worse when the volume is higher.

Anyone know what this is?

Hmm. Does it happen when you move the camera around while stationary?

@rorie: No I don't think it even happens when I'm walking around. If it does it is random.

Edit: What I mean is the game is fine until a loud noise happens. The scratch/buzz will happen then. Looking around for supplies I won't hear it, gun fights I'll hear it a lot.

So this happens with other games also? Have you disabled the 5.1 audio output in the PS3 audio settings? Because that might screw up the audio mixing. Also check all the cables that they are plugged in propely.