This is so stupid. Your CAPTCHA is unusable by blind people, and your audio CAPTCHA is inaccessible (you have to see the <canvas> element to know where to click to access to the audio CAPTCHA).
Do you consider that blind people are bots?
Do you consider that blind people are bots?
Screen readers should pick up the alternate text.
<a href="javascript:AYAH_fallback()" style="position:absolute;left:-10000px;top:auto;width:1px;height:1px;overflow:hidden;">Please complete this audio captcha before submitting the form</a>
Also, I know the audio sucks, but it's the most secure out there, otherwise it would just be a giant hole for bots to get through. It's one of the things we want to make better.
In fact, we've experimented with audio games and had some good results.
I agree that the button itself should be easier to discover for blind people, like an image link with a title tag.