Mac users need to do an extra step: you need to right-click (or control-click, depending on whether you have a 1 or 2-button mouse) on the Full Tilt application icon.
That reveals the Contents folder. Open that up and voila, the motherlode! All the sounds are in the folder called Waves. You should be able to move these over to PokerStars by following the same steps (right click, etc.).