Try to get it on a lift and isolate the sound. I'm betting it's a wheel bearing. See if it does it when you enter a curve going left and right. Sometimes wheel bearing sound will go away if you have the wheel turned one way or the other.
Just FYI on my tundra the service history shows this:
"
FRONT SUSPENSION
FRONT SUSPENSION ~|~CUSTOMER STATES HUMMING/PULSATING NOISE AT 10-50 MPH. JUST HAD REAR WHEEL BEARINGS REPLACED. BOTH SIDE. ~|~NOISY LEFT FRONT WHEEL BEARING VERIFIED ~|~REPLACED LEFT FRONT WHEEL BEARING ASSEMBLY - ON FOLLOW UP ROAD TEST ANOTHER ABNORMAL NOISE WAS DETECTED - REINSPECTED ALL WHEEL BEARINGS WITHOUT DISASSEMBLY AND NO ISSUES NOTED - FOUND ONE OF THE RIGHT HAND WHEEL BEARING STUDS IS NON-OEM - CHECK VEHICLE D
PARTS
NAME PART # QTY
BEARING ASSY, FR AXL 435700C010 1
RING, O 90301A0020 1
SEAL, TYPE V OIL 90312A0002 1
BOLT, W/WASHER 90119A0277 4
CUSTOMER PAY
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However I would not assume or guess. It should be pretty easy to figure out where the sound is coming from if you have it up in the air. Can the people doing the timing belt swap ID it?