Audio captcha is supposed to be a solution for those who can’t see properly or have problems with figuring out the written texts on the captcha image, but it looks like the audio version is not better.
Is it really that bad?
The following captcha videos say it is…

As you may already know by now, Captcha is a common approach to prevent access of users that aren’t human to all kinds of websites. The captcha is a kind of test that requires verification of distorted image plus textual content which is deciphered easily by humans but not by computer bots. 
However, it appears that [...]

Audio Captchas are an alternative for people who suffer from sight impairment and thus are unable to solve regular textual or image Captchas