if you have your ringer turned to silent (the volume rocker bar all the way down) there's no camera shutter sound.
I don't like the sound because i'm a hunter and if a animal comes by that i don't intend to shoot, i can take a picture of it with no camera sound.
I think that's the focusing mechanism that makes that noise. No chance of stopping that at startup. That thing really makes a racket when I'm using a barcode scanner app.
-SR-