Playstation 3 will play sound when on menu, but not when in a game. Anyone know how I can fix this?

So I brought my ps3 to my clients house cause I thought she would get a kick out of playing Kingdom Hearts. I hooked everything up and used my own HDMI cord, and could hear the sound of my ps3 when it booted up. I could even hear the music from the game in the menu, before pressing it to play. But the moment I turn on the actual game, there's no sound.

I've never seen it where the ps3's homescreen will have sound, but not the games. I tried Portal 2, and it still didn't work. Does anybody know how to fix this? I know they have a sound bar, I'm wondering if that has to do with anything.