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I accept that 16/44.1 CD format is adequate, in theory, for almost everybody. I'm also willing to believe that some people perceive (not HEAR, but PERCEIVE) frequencies above 20kHz.
According to one study, people can hear up to 25kHz at extreme volumes. At normal volumes, one theory is we can perceive UHF via some other pathway, like eyes or skin, yes, which means that it wouldn't work with headphones.
The original Oohashi experiment did note it didn't work with headphones, and the study has never
really been perfectly replicated and refuted... that is, with
fMRI, gamelan music, super-tweeters, whateverz... so the findings still stand in that sense.
I suppose there are some perceptions which are too complicated to ask "yes / no" and tick boxes, you need to look inside their head hahaha. It's like subliminal advertising... "did you just see a subliminal advertisement? Yes / No" ...............................
Perhaps... if a room is painted blue, versus red, and you're trying to find out if the colour of a room affects peoples mood, without telling them what the study is about, you usher 20 people into different coloured rooms and make them tick boxes, you see that's difficult as well, since it's a study on emotion there are no clear-cut limits, unless you want to measure levels of cortisol in their blood after being in a red room for hours.
Anyway there is one modern paper which 'proves' that we can perceive higher-rez material than 44.1 kHz, but the statistics aren't very good in it, I'm not sure if it's valid, in my opinion (if it's invalid, I suppose that says something about the validity of all other papers listed at the AES) -->
http://www.aes.org/e-lib/browse.cfm?elib=15398
What I did like about it, is they didn't use the common fast switch, time-aligned ABX, which imho is very overrated. Someone really needs to write a new blind-test program for Foobar, without the immediate switch (like a 10 second break between A... A... A, versus A... B... B..., and not time-aligned, the sample is played from 0 - 20s, etc.).