Can Anyone Use Audio CAPTCHA?

I recently met a blind student and added him to my LinkedIn buddies. As many of my readers will know if you log on to LinkedIn the first screen you get is a CAPTCHA (Completely Automated Public Turing Test To Tell Computers and Humans Apart) screen.

I realised that the pictorial CAPTCHA would be a problem for my new friend so I thought I would try the alternative which is an audio CAPTCHA. I tried it several times but the voices are so distorted and intermingled with background noise that I was unable to type the right words.

I asked him if he could hear the words and get them right. His answer was that he had tried a few audio CAPTCHAs and had never succeeded so instead he uses a special service for people with vision impairments called WebVisum, which takes the visual CAPTCHA and returns the right words in a scratchpad that he copies and pastes into the answer box. I do not know how WebVisum works but I assume there is an element of human intervention required.

A system is only accessible if it can be used by the real user. Audio CAPTCHA is a technique designed to be accessible but it appears to be failing the real accessibility test. My survey so far has only been of two people so I would like to gain some more evidence that they are unusable. Next time you are faced with a CAPTCHA screen please could you try the audio version once and see if it works for you. Could you then add a comment to this blog to say which website you were accessing and wether you succeeded or failed.

If audio CAPTCHAs are not usable by a significant number of people then we should stop fooling ourselves that they are a accessibility technology and the industry needs to look at alternatives such as the verbal puzzles used on some sites.

Peter is Practice Leader (Accessibility & Usability) at Bloor Research. Peter started in IT as a sandwich student in 1966 with IBM and continued to work for them until 2003. In a company then known especially for its hardware Peter saw the importance of software and especially transactional processing. He installed the first IMS online system in the UK as well as early versions of DB2. In 2004 his experience with some disabled friends and a report by the Disabilities Rights Commission prompted him to start research into IT accessibility for the disabled. Recognising the growing importance of this area he set up Bloor's Usability and Accessibility practice.