Sound problems with some ps3 games

Hi, Im having some problems with sound in a few games, its really making arkham asylum unplayable for me, and I have had it before in the mgs4 cutscenes.

In batman I hear the voices fine (when people talk in person or through the intercom) but then when I move the camera away from the voice source, I cant hear anything at all! I really find this so frustrating and its giving me a sore head, I just cant get into the game at all. I think its a problem to do with surround sound, but all my settings on ps3/tv are set to stereo, which is what I use, it just feels like its transmitting to a surround sound system. Im using hdmi for video and audio.

I also get this problem in mgs4 during the cutscenes, its really annoying. I think I get it in some other games as well, but it really hasnt effected it too much.

Has anybody else had this problem before or know how to fix it?

Cheers,

Dominic.

Has nobody else had this problem? When I look away from the sound source I hear nothing, as if it should be coming out of the back speakers if I had a surround sound system, really annoying.