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Why Audio CAPTCHA Doesn't Solve Accessibility

When we mentioned yesterday that one of the problems with web site CAPTCHA forms is that they aren’t accessible via screen readers for the blind or visually impaired, several readers suggested the ‘audio CAPTCHA’ buttons seen on many sites were an acceptable alternative. Unfortunately that’s not the case, as ACCAN disability policy advisor Wayne Hawkins explained to us.

Waveform picture from Shutterstock

“That’s a common misconception that audio CAPTCHA solves the problem,” Hawkins, who is blind, told Lifehacker. “Whilst one would imagine that would be the answer, those actually often are just as inaccessible.”

The biggest issue with audio CAPTCHA is actually the same as with the visual version: just as it’s often hard to see which individual letters are being used, it’s hard to distinguish individual sounds. “One of the problems with audio CAPTCHA that I’ve found is similar to the visual CAPTCHA: there’s so much noise behind the words that are being spoken you can’t identify what they are,” Hawkins said.

That noise is added to block automated recognition systems, but in this case the cure seems worse than the problem. “I pride myself on being a pretty good listener,” Hawkins said. “Because I’m blind I need to use my hearing in different ways and I find even with that very acute hearing that these audio CAPTCHAs are really difficult to understand.” In one case

A secondary problem is that audio CAPTCHAs often use numbers, but doesn’t distinguish them, so it’s impossible to know if you have to type ’1′ or ‘one’ or ‘won’.

The solution, as we said yesterday, is to ditch CAPTCHA altogether. Sending a verification email is one solution, though that adds an extra step. Another good alternative is asking site users to solve a simple maths problem — an option that works well with screen readers, Hawkins said.