G'day Oskar,
BTW, if people use browser unable to display images, how much would an audio captcha really help (I mean, sound's way more hi-tech)?
Some people use browsers that cannot display images because they're blind. In such cases, audio is a Good Thing, and use of images specifically designed to be unreadable to computers is not.
-- Mark Gallagher "What? I can't hear you, I've got a banana on my head!" - Danger Mouse