"Ironically if I see an audio capture I tend not to bother with it because it's usually such a poor experience... some of them sound like aliens talking and they put weird background noises over them. They are a bit of a joke in the blind community. I've spent half an hour on some and had to give up."
Have you ever tried the audio of the captcha? I tried it a few times and found it to be as bad, if not worse than the visual display.