I haven't done anything to mine yet except take the top lid off and look at it. Interestingly, when unscrewing some of the lid screws, the fan noise went down substantially, and with the lid just sitting on the top, its quieter than if you put your palm on the lid. There is certainly some degree of lid vibration at play.
Looking at how the fan is mounted to the aluminum plate, I see no rubber spacers or anything. The fan looks like its mounted right against the metal. and a nut and bolt goes through each corner of the fan, which again appears to be metal on plastic, no spacers or isolation sleeve etc. I'm curious as to why they couldn't use the normal computer fan style mounting where you've got the silicon posts with a lip on them. You just pull them through the opening and the lip pokes out the other side, holding it in place against that aluminum riser platform, yet keeping the fans vibrations dampened from the underlying structure... The way its currently attached the fan and the aluminum plate are one solid piece, no dampening at all.
If I pinch the side of the aluminum plate between my fingers the vibration is cut way down. I don't know if maybe they forgot to add a little gasket material that was supposed to go under the fan, or if they just tightened it too much, but it seems to be the cause of the noise and its making different parts of the case vibrate.