Yea, I almost went with the gold/yellowish rotors, but supposedly they have even more road noise. One day Ill find the perfect setup for me. Sadly, its probably the $2500 front kit they sell. lol
It's just air passing over the rotors in the slots, the reason the USR are meant tone the quietest slotted rotors are due to the slots being broken up in half, 2 small slots = less wind noise than 1 large slot.
Brake aerodynamics, LOL! I'll have to pay closer attention to mine for sound now. I have only heard the periodic chuk chuk chuk where the slots & holes are in the rotors, but no humming of any kind.