Humming/Squeaking Brakes

I have a 2006 Hyundai Elantra Hatchback with 82,000 miles. From the drivers-side rear tire I hear an occasional humming/squeaking that will stop and not continue if I apply the brakes. The noise most of occurs at faster speeds 60-70 mph and will happen for only a few minutes during a few hours of driving. Recently the noise as become more frequent and at additional speeds. Please help; brakes, bearing, cupped tires?

Sounds more like a bering possibly going out, but it could be a number of things. your best bet is to take it to your mechanic and have them diagnose the problem.