Hums/buzzes are always difficult to diagnose. Could be a number of things, from the cowling (black plastic around wiper motors against windshield) to engine noises. I would advise parking it in the driveway and having someone rev the engine up slowly, see if you can hear it. If you can't hear it there, most likely wind related. If you can hear it parked, then engine related. That will at least narrow it down.
Just don't rev it into the red.
[COLOR="Silver"][B][SIZE="3"]2012 Jeep Compass Sport 4x4[/SIZE][/B][/COLOR]
[I]2.4L I4, CVT II, Freedom Drive I[/I]
[COLOR="DarkSlateGray"][B][SIZE="3"]2010 Dodge Dakota Quad Cab 4x4[/SIZE][/B][/COLOR]
[I]4.7L V8, 545RFE, Big Horn Edition[/I]