I had my drivers side bearing make a noise similar to this. Thought it was the axle and as I popped the axle nut loose I noticed that the bearing was coming with it, in 2 pieces lol... It separated and left part of it in the knuckle which I had to hammer out. Also had no ABS light on.
Just because it's in neutral on the highway doesn't mean that the axle isn't spinning. After all, it is locked into the bearing with splines and a rather large nut at the end. The trans. just disengages the gears, but not the axle so it could be a bad axle as well. If you need to replace it I'd go with a Napa axle or OEM Delco one as most others seem to die rather quickly.
