Humming noise at high speed

I have a 2005 Tacoma SR5 V6. At around 70MPH I hear a noticeable humming sound almost like a reverberation that sounds like it's coming from the front end but, of course, that may really not be where it's coming from. There appears to be no change in pitch if I accelerate or drop speed. Also does not change in a turn. It goes away around 50 MPH. Wheel bearings are tight as is the universals joints. My truck has 87,000 well cared for miles. Any ideas?

 

Rear wheel bearing

this happened to me back when I only had 30k on my truck. It sounded like it was coming from the front but ended up being the rear passenger.

 

Passenger?

But seriously, I'd rotate tires and see if the sound moves.

 

Rotate tires to rule out scalloped tread. Spin the truck up on a lift and if the rear bearings are bad they get SOOOO LOUD.

 

Wheel bearing like others have said ... or if you have new mud terrain tires they are just loud.