reCAPTCHA: audio alternatives and audio formats

aloha, all!

concerning the cascade of aural CAPTCHA equivalents, i have pondered
the issue of baseline audio formats for quite some time, but can't 
find the post i was preparing on the topic, so i'll just simply ask: 
what is the cascade order for aural filetypes in the real world 
today?

   .ogg
   .mp3
   .au

1) is .au the baseline for web delivered audio content?

2) is .ogg widely enough supported to retain first place in the cascade?

3) are there any widely supported (read old) filetypes that are not
included in the cascade order listed above?

4) are .mp3 files capable of being played using the user agent or 
operating system's default sound renderer?

5) is this the same cascade that should be provided for aural slash 
speech CSS, versions 2.0 through 3.0?

gez, does WCAG2 advise content providers to provide a cascade of sound
formats, so that everyone will be able to play them without invoking a 
third-party media player...

has any thought gone into serving up pure sounds (dog bark, duck quack, 
train whistle) to defeat the voice-recognition?  this would involve a 
quick lookup for the appropriate answer in lang="x" or, through 
content negotiation serve up a version of the CAPTCHA that corresponds 
to the requesting user agent's language preferences, which would make 
the verification look-up faster...

gregory.
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"Half of expertise is tease."      -- Harry Shearer
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Gregory J. Rosmaita: oedipus@hicom.net
     Camera Obscura: http://www.hicom.net/~oedipus/
United Blind Advocates for Talking Signs: ubats.org
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Received on Tuesday, 17 July 2007 16:03:36 UTC