This is nominally a technical subject, but there’s really no reason to link to it except the discussion of various countries' policies about, yes, upskirt photography and other non-consensual pictures. As such, I voted that it’s off-topic.
The interesting part is the first accepted answer.
Playing the inverse sound when taking the picture cancels out the shutter sound and defeats the intended limitation.
Huh. I admit that’s a really cute trick.
In Japan for example you can’t do that. There the shutter sound always plays even if you muted the phone. (Some weird rules to prevent privacy infringement, aka upskirt photography are in place in Japan as far as i know) So I don’t think there is a way to do that. – Dunkelstern Dec 16 ‘10 at 15:28
There are signs in the subway in Tokyo warning women to look out for people trying to take upskirt photos. No idea how often it actually happens though.