Loud humming/spinning noise at high speeds

4 cylinder, automatic 70,900 miles.

My vehicle makes a loud humming/spinning noise that seems to be coming from the rear. When I exceed 40+ mph the noise appears and goes something like wom wom wom. The faster I get the louder the noise becomes. But once I past 65 mph the noise isn't as pronounced as lower speeds. I suspect it is my tires but i'm not sure. Also the noise is only dependent on speed, its the same whether I brake or accelerate.

My tires are Riken Raptors.