HDMI audio settings on Hitachi 42PD6600 for PS3?

Ive connected my PS3 to a Hitachi 42PD6600 via a HDMI cable. Picture is perfect but the sound seems muffled, like whilst playing Fifa 09 the commentators voices are barely heard, or on Buzz the voice guy who ask questions cannot be heard. Im not sure which audio I need to choose on the PS3, I leave it automatic thats when i get problems, tried a few of the other options but no sound can be heard. Anyone help?