60mm 2.8 Autofocus noise.
If I put my ear up against it I can just hear mine over the optical stabilizer buzz.
I have been testing the lens in my room. It is quiet enough to hear the IS which you really don't in a normal environment. I am sure I won't hear the focus noise when using outdoor, but it is definitely noticeable compared to my other lenses with MSC so I was little bit worried.