One thing is the shutter itself. It's, as has been said already, quiet enough. Maybe not as quiet as a film M, but close enough. But I find it strange that noone has pointed out that you on a film camera need to advance the film, and that's not exactly a quiet affair, especially if you have to do it quickly. So even if the re-cocking of the shutter is a little loud, I think it's quieter than the film camera if you consider the speed.