Well, checked bearings, they appear ok (no movement). Front tires are ok (even wear). Back tires have uneven wear (inside worn more than out), so didn't want to rotate them.

Further analysis of the "noise" is that it almost sounds like it could be the differential or drive shaft, maybe even the tranny(???). As described above, it's a rumble or "roaring" sound that comes up into the car from the floor, I'd say mostly the front. Again, noise is affected by speed of car. Like when I slow down, the sound changes as the rotation of whatever it is making this noise slows down, the noise itself winds down. Guess I can't rule out tires until I put a different set on. Any thoughts?