Did you recently do plugs or wires? The reason I ask is because the other day I was messing around under the hood of my car and had the "cover" thing off. I put it back on and went for a good long road trip. Almost instantly I heard a BAD whining noise. I was worried it was something serious. The car still ran great just S/C was loud. I got it home and figured out that I had pinched some plug wires under the lip of the cover and it had not "seated" right. I fixed it and the noise went away.