This really is a fine camera. A great lens, reasonably small and foolproof. But it's not perfect. I agree with the comments that the film and rewinding is a lower frequency whir, definitely less noticeable than the higher-pitched "eee" you get more typically. There is a noise associated with the lens moving into position right before the shutter fires.
Even if you prefocus, the lens will then move out to take the picture, then retract to its resting on position. So in addition to the noise, there's always some shutter lag. There is no noise when you prefocus; it's just after you trip the shutter. I wanted to point out to you about the shutter lag, in case you're thinking this is a "decisive moment" camera.
There is also noise when you turn the camera on -- sort of a "bzz-clack" as the (flimsy) lens door slides open and the lens extends. So if you want to be stealthy, you may need to keep the camera on and protect the lens. (And, as someone else mentioned, be sure it's set to "flash off" or you'll certainly not be stealthy.)
