Engine Sounds Like a Propeller

I was wondering if you guys could offer me a little advice. I have a 2002 Impala LS with 105,000 miles on it. I recently have been hearing a loud humming noise from the engine compartment. It almost sounds like an exhaust leak, but looking through some previous posts it could also be the torque converter, the lifters, or the alternator. The noise does not seem to be effective by RPMs rather the speed I am going. 50 miles per hour has the loudest humming, while 80 is fairly quiet.

Has anyone run into this before? If so, how can you tell what's making the noise.

Thank you!

if you have no noise when the car isn't moving, I'd rule out the torque converter. since it's not affected by RPM, I'd rule out the lifters and alternator. Sounds like a bad hub bearing to me.