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Public AAC Listening Test @ ~96 Kbps [July 2011].
The folks at the Hydrogen Audio Forums have for years been benefiting the world with their patience, technical skills, and hyper-focus on sound quality, by comparing the real-world sound of various codecs and bit-rates for audio encoding. Under the scope for the latest public listening test (slated to run until July 27) are the following AAC encoders: Nero 1.5.4; Apple QuickTime 7.6.9 true VBR; Apple QuickTime 7.6.9 constrained VBR; Fraunhofer (Winamp 5.62); Coding Technologies (Winamp 5.61); and ffmpeg's AAC (low anchor).
I too had this same question awhile back. Why doesn't HA test commonly used codecs at, say, 192kbps or 256kbps?
The answer? the tests fail because nobody can tell the difference. they make for very boring results.
they run the test at 96kbps because they get usable results. people over a wide range of sound systems and hearing conditions can provide usable responses.
What would you do with that data? hard to say. you can't really extrapolate that, say, if codec A is better than codec B at 96kbps, the same will hold true at 192kbps. In fact, I've seen the direct opposite of that in past HA tests, where various codecs trade the lead depending on bitrate.
So "who is 96kbps for?" I don't know. but "why test 96kbps?" that's easy.
I heard the difference between an iTunes-encoded 320kbps MP3 and FLAC in 2/7 samples I used. This is through ABXing and using statistics. Granted, these samples were chosen as good examples that show differences between lossy and lossless. I wrote up a series of blog posts on it here: http://www.vel.co.nz/vel.co.nz/Blog/Entries/2009/8/21_ABX_of_Lossless_versus_MP3_-_Part_3_-_Results_and_Discussion.html