But your analogies aren't actually correct.
When HD TVs (1920 x 1080) first appeared, it was NOT universally agreed that the extra resolution actually made a significant difference for most customers. Many people in fact argued that there was very little HD content available, and that using "full 1080p HD resolution" on a screen smaller than 30" was a total waste anyway - because nobody could see the difference between 720p and 1080p on a screen that small. However, today, almost every TV of any size is full 1080p HD, and we're having the same argument about 4k.
The problem with your argument is that the basic premise is limited. Yes, if there was absolute reliable proof that frequency response above 20 kHz absolutely, positively produces no audible difference, then it would be unnecessary (although I'm still not convinced that having a "safety margin" above the bare minimum isn't still a good idea). However, the proof you're offering isn't at all "absolute" or "conclusive". In fact, most of those tests were conducted with inadequately sized sample groups, using obsolete equipment, and frequently conducted using dubious test methodology. The fact that twenty or thirty people, using 1980's vintage technology, and 1980's vintage recordings is NOT compelling proof that the difference doesn't exist - at least not to me. And, if we were in fact to prove, with properly sized and run tests, that the difference wasn't audible with the best equipment available today, that wouldn't constitute evidence about whether there might be a difference that is audible with the equipment available in twenty years. I simply don't believe that we actually understand 100.0% of how human hearing works; especially since human hearing takes place partly in the brain - and we certainly don't understand anywhere near 100% of how THAT works.)
(The reality is that there have been several tests run in recent times which tend to suggest that frequency response above 20 kHz can in fact produce audible effects - in different ways and with different implications. The recent AES paper seems to show that a small sample of individuals was able to "beat the odds" in terms of telling whether a given sample was high resolution or not. Another test I recall reading about produced a result that demonstrated that, while the participants didn't hear what they considered to be an audible difference with band-limited content, the location of instruments in the sound stage was perceived as being shifted with the band-limited version, which is in fact "an audible effect". Note that I don't consider either of those results to be "compelling" either but, when balanced against tests run decades ago, with the audio equipment then current, I think they raise enough questions to make it unreasonable to "fall back" on those outdated results as being "absolute facts" without confirmation.)
I don't believe that the analogies are incorrect around the basic point. Increased bit depth does increase the quality of video due to pixilation, but does not increase sound quality in audio beyond 16bit because the sound wave is already perfect and all you are doing is increasing the dynamic range and lowering the noise floor. That extra video resolution of 1080p was not agreed to be an improvement back in the day is neither here or there. The limitations were largely as you say the screen size. With audio, the limitation, beyond 16bit, is not the hardware but our ears. Whereas the eye can determine high res video due to smaller pixilation, there is no pixilation in audio. If you can actually find a home consumer DAC that can actually resolve 24bits, and have the equipment to go with it, it will not make the sound wave more perfect than 16bit digital or 8bit digital for that matter.
The analogy of going beyond 20khz in audio with TVs being able to reproduce frequencies into infra red is valid. In both cases there is no point as it is outside the human range. I don't disagree that higher frequencies than 20khz may produce audible effects, but this is more likely to be distortions in the stereo system reacting to ultrasonic content. There is documented evidence that 24/192 can cause distortion is some stereos because of it.
The bottom line is that you appear to be challenging the established known facts that humans can't hear well above 20khz and can't resolve a dynamic range greater than 16bits. This is a bit like challenging the notion that humans are unable to pick up sonar signals like dolphins and bats. Surely the burden of proof is on those making the claim. And using special pleadings such as "we do not know 100% how human hearing works" to somehow justify then that means we can hear ultrasonic sound waves or have machine like resolution is a well know ploy used in most psuedosciences.
Just to be clear - I'm not actually challenging anything one way or the other - because I haven't run a properly controlled test (and, again, even if I personally couldn't hear a difference, that wouldn't prove that nobody can). My main point is that "the established science" may simply not be right. Five hundred years ago, the established science they taught in school was that the Earth was flat, and tomatoes were poisonous; now we know better. When I went to high school, they taught in science class that all matter was made up of protons, neutrons, and electrons - which were the smallest indivisible "pieces" of matter; and that model was good enough to bring us nuclear power plants and the fusion bomb; but now we find that notion quaint, and there's an active debate about whether matter is "really" vibrating 11-dimensional energy strings, or a collection of smaller particles called quarks, or something not quite either one. And, the last time I looked, we
still don't know exactly how the human brain works (and "hearing" occurs in both the ears and the brain).
Incidentally, for an interesting experiment, go buy yourself one of those new souped up half watt LASER pointers that operates at 720 nm or 840 nm; that's the "invisible infrared" color used by a lot of remote controls; and a LASER puts out a very clean single frequency. Shine the dot somewhere and you will probably find that the "invisible" dot is in fact clearly visible; I can see it quite clearly as a pale pink - and so can most people. So I guess the "science" about IR light being "invisible" is wrong too. (Actually, in order to be visible to most of us, it has to be so bright that it is somewhat dangerous to look at for more than a few seconds, but my point stands - the "commonly accepted fact" is in fact
wrong. And, in fact, a TV that was actually able to display long-wave IR, and so make the bright sun in the picture of the desert actually feel warm on your face, would - at least to me - have much better fidelity than the one I have now.)
I don't know for sure whether the difference between 16/44k and 24/192k is audible - everything else being exactly equal, but I'm absolutely positive that I don't necessarily trust the "truth" as "discovered" by scientists back when most audiophiles were certain that a Dynaco Stereo 70 and Koss pro4AA's "sounded audibly perfect" because both "covered the entire audible spectrum". And, with many modern DACs with selectable filters, there are differences that many people find audible which
seem to coincide with different sample rates and different filter responses producing audible differences. Perhaps there's something there; or perhaps what we're hearing is simply that a given DAC handles 16/44k differently than it handles 24/192k - because it uses a different oversampling multiple; and perhaps the endless discussions in one or two pro sound forum about how certain sample rate converters sound better or worse with certain types of music is all superstition as well (audiophiles have nothing on pros for superstitious beliefs). However, I'm not quite prepared to say that "audio science is at its end because there's lots of equipment available today that's audibly perfect, so there's nothing to improve."
Personally, since the science shows clearly that high-res files are in fact superior in quality (frequency response and dynamic range) - whether that superiority is audible or not - then to me that's enough justification for continuing to improve things.... and for studying whether those technical improvements lead to some sort of audible improvements. I can also say that, personally, I'm willing to pay a bit extra for a technical improvement even if that improvement doesn't yield anything that's currently important - or even noticeable. (If it turns out that nobody can hear the difference, that still won't prove that the extra information that's there won't be useful to some new "3D decoder" someone comes out with next year, or some other gadget neither of us can guess at, and so won't prove it "totally useless".) I also simply see the latest "fad" for high-res remasters as being generally a good thing - because at the very least it encourages people to listen to music carefully enough that they are actually hearing it. (I'd rather see people spending money on high-res players that don't sound different than on cheesy 128k MP3 players which they imagine "don't sound
much different" - because the latter is a slippery slope I'd rather avoid approaching.)
Now, if you want to start a new thread entitled "What is the best and most practical sample rate and bit depth to use for distributing consumer music?" then I might well be inclined to agree with you on a lot more things.
