gymrat...that's almost undoubtedly wheel bearings.
Test it on a highish speed turn. The loaded wheel will 'whoop whoop' ...so left wheel on a right hand sweeping turn. If you're hearing it on a straight, it might be tires or a really bad bearing. See if you can change the sound from different direction turns.
With a tire, it could be a bad flat spot from having sat for a long while at normal or low pressure. After a couple of weeks of sitting, you can usually work it out...but if it's sitting for a long while, that flat spot might be permanently in the tire.
Still, the sound 'sounds' like bearings to me. Test it on turns and see what you get.
dmax on the radio--answering all your car questions as best I can!
watsonnwatson.com every Wednesday at 9 p.m. NYC time. Call in! (661) 449-9340 Click "Watch and Chat"
Please 'friend' me!