johncarm
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Yes, from the point of view that psychoacoustics is merely one branch, a sub-set of sound science.
No, here we don't agree. Commonly today, particularly in the audiophile sector of the market, audio design is dictated by marketing departments rather than by engineers or scientists. Marketing depts are commonly unconcerned about whether there is a difference, whether or not it's potentially audible or, even if "yes" to both these questions, whether or not that potentially audible difference is actually an improvement. As far as marketing depts are concerned all these issues can easily be overcome with standard, long established marketing techniques (pseudo-science, doctored comparisons, testimonials, shills/incentivised reviewers, etc.), there are much bigger fish to fry! For example, many/most/all audiophile DAC (and DAC chip) manufacturers would consider supporting the 192/24 (and higher) format/s to take precedence over the fact that the only potentially audible difference is actually a loss of fidelity (compared to lower sample rates/bit depths).
G
Regarding the question about the differences between two sources A and B in the case that the null test reveals a peak level of -100 dBFS.
You say that some situations don't require psychoacoustics to make a determination. But it seems to me like you are invoking psychoacoustics twice in saying that A and B are indistinguishable.
First of all, the null test gives us the signal A - B. But that's not what we hear. We hear A first, and then B. Who is to say that we actually perceive the signal "A - B"?
I mean, if we do something like take some music A and then add a signal B which is a sine wave at -20 dBFS, then we probably would hear B it's own separate signal. But what evidence is there that we hear, in the general case, the difference between A and B as "A-B"?
Second, you said that a signal must be at least at the level of the background noise to be audible. Now I don't know if this is what you were saying, but doesn't this require psychoacoustics to determine? I'm thinking of how the background noise might be pink noise, while the signal is a pure sine wave at 2000 Hz (a pretty sensitive band of the ear). Whether this is audible is a matter of psychoacoustics and requires experimentation, does it not?
It may be true that audiophile design is dictated by marketing concerns, but ultimately I'm interested in what's really true--what differences are really audible.
Maybe we should get more specific. Let's talk about high bit rate/ bit depth formats. What does the evidence say? What bit rate and depth is essentially perfect? (That is, no higher rate/depth would improve fidelity.) What is the evidence for this?