This very same thing happened to me at the same speeds roughly but on the passenger side. My issue was in fact the wheel bearing that had worn away and needed replacement. After repairing, there was still a noise and slight vibration which was actually coming from the tire. Upon inspection, the tire was chewed up a fair amount on the tread, as though it was skipping along the ground. Replacing it as well as the rest of my tires (they were about due for replacement anyways and the shop had a good deal on 4 of them) completely eliminated the noise and vibration.