14 DAY TRIAL // A captcha is an image that will be shown on some sites that require a verification word before loging in. The picture will display a blur text that must be typed in the box placed near the image.
"Captchas were never intended to be purely visual -- however, most initial implementations used fuzzy images, and in attempting to lock out automated agents also inadvertently locked out people unable to see the image. As an alternative to these, this past spring Google Services that require verification began to provide an audio alternative -- people have the option of listening to a sequence of spoken digits that they then type into a form field to verify to the web application that there is indeed a live human at the other end," T.V. Raman, Research Scientist said on Google's blog.
Google's initiative is really considerable because it can help blind people surf the internet with ease, without having to know what a picture shows using a simple audio file that will pronounce the letters you must type to access the site.
"To keep the audio captcha as challenging as the visual captcha when confronted by automated agents, we add some distortion to the spoken digits, and we're still experimenting with different distortion techniques to ease the burden on the genuine human user while locking out automated agents.
You can easily spot the availability of audio captchas by the presence of the well-recognized "wheelchair" icon for accessibility --- the image is tagged with appropriate alt text to help blind users.
Incidentally you don't have to be visually impaired to use the audio captcha; if you are in a situation where you find it hard to view the visual captcha -- either because you're at a non-graphical display, or because the specific visual challenge we offered you turned out to be unusable in a given situation, feel free to give the audio captcha a try.
We've worked hard to ensure that the audio captchas work on different hardware/software combinations, and you do not need any special hardware (or software) other than a sound card to be able to use them," it is also mentioned on the blog.