Can anyone use audio CAPTCHA

Peter Abrahams

Written By:
Published: 11th October, 2010
Content Copyright © 2010 Bloor. All Rights Reserved.

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.

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