2000 Pontiac Grand Am Sounds like a "Prop Plane"

My car has a new noise that I noticed just the other day. It has started to sound like a "propeller driven" car! (EXACT same noise as prop.)
Has no relation to the engine speed. Just speed of vech. As I go faster, it gets louder, 'till you hit around 55mph, then "seems" to get quiter. But does NOT go away until I stop at a light. Slow down below 20 mph)

If I take a hard right turn, seems to lesson a bit. Poss go away.
I'm thinking CV joint. But how do I know which side? Could it be anything other then that? (I pulled the front wheels and looked for bad boot. Slop. But all looked good. So I can't tell!) Should I be worried about catistrophc failure? (Sp?)

Where should I be buying these parts? (Is it a better part @ the dealer?)
Thanks, Don M.