No matter how hard you try to weed out automated scripts and computers from taking advantage of services you offer, some will almost always find a way through.  A lot of websites use captchas to try and verify the humanity of a visitor.  You've seen them.  They're those odd strings of letters and numbers that get all jumbled and distorted that you have to type in before submitting a form or signing up for a service.

The Google Blog has a post about using audio captchas in place of the standard visual ones.  The audio captchas serve two purposes:  1) they allow visitors without sight access to your service and 2) they prevent even more computers from sneaking their way by your preventative measures.

Despite the title of my post, audio captchas aren't typically musical.  The Google ones, at least, are spoken strings of letters and numbers similar to the visual strings you're already familiar with.  Just as the visual strings are normally distorted, so too are the audio captchas.

Google is soliciting feedback and suggestions on their implementation of audio captchas.  If you run across them while using your Google account, drop them a line and let them know about your experiences with them.

If you operate a website that utilizes captchas, consider implementing audio versions to allow unsighted individuals access and to boost the filtering ability of your service.  Besides, even sighted visitors can use them.  Sometimes it's hard to read the string of characters you're expected to type in.

Having an alternative will allow more legitimate access to your site.