The reason you can't get sound coming out of your TV is because you haven't hooked up the Macbook's sound port to the TV. The video out on the Macbook is just that, video.
Check to see whether your TV accepts a 3.5mm audio jack, the type that's on headphones. If so, then all you need is a simple male-to-male 3.5mm cable (you can pick them up real cheap at local electronics stores). Connect one end to your Macbook's headphone jack and the other to your TV.
Now, I know that the Macbook also offers optical audio out, but I'm not sure how one would go about hooking that up. Perhaps somebody else can shed some light on it.