Where does it sound like the noise is coming from?
I get the same kind of noise (faintly) but it sounds like its coming from outside the car on the driver side or inside behind the drivers seat. I only hear it when the driver window is all the way down. Yes i checked and it not the seatbelt. I never let it concern me but am curious now that you mention something similar.
I have a noise that kind of sounds like that. It comes from the speedometer cable that needs lubrication. It only does it at highway speeds. If you do a search there are posts on here that explain how to lube the speedo cable, it's a common problem, on older bulls anyway.