so first promised, first answered:
How many Hs are needed to test a missingF?
Looks like many have forgotten that
giant open question in the OP. It's ~impossible to settle the bet without clarifying it. May be possible to settle for the "audible" side without an answer but the (much harder) proof for "not audible" cannot work without a clear answer.
courtesy of
@kemmler3D 's nice bats & a lot of googling, we finally have some answers.
Smoorenburg (1970) developed a .. test in order to test the predominance of pure tone versus collective pitch sensations.
... for two-tone stimuli less than half of the tested subjects spontaneously classified most of the sequences according to their collective pitches ... subsequent experiments revealed that the proportion of ‘‘collective pitch perceivers’’ increases with the number of presented harmonics...
(note: the "collective pitch" is the missingF. No need to take my word, the bats-study is linked above)
The quick takeaway: two Hs are definitely not enough to test. 3 Hs don't seem that great either, particularly for the "not audible" proof. I did not find a clear "you must have xx Hs" statement but 'everything' seems to point to "4-5 or more"
Some of the bat guys used 4+ harmonics
..trained to .. classify the collective pitches of complex tones, consisting of the first four harmonics
Everyone else seems to be using 5-10 Hs and 4 is a sort of "absolute minimum":
Ritsma (1962) and Plomp (1967) conducted experiments indicating that the harmonics contributing the most to the pitch of complex harmonic sounds were in the region of the second to fifth harmonic. These second to fifth harmonics of a harmonic complex were dominant in determining the pitch of complex harmonic sounds
The encircled "dominance region for pitch" is what ~every other study uses. The number 5 looks a bit arbitrary and I find it somewhat counter-intuitive that the H6+ contribute so much less. And the H10+s have zero effects, even when they are in our "most audible" 2-4kHz range.
Counter-intuitive or not: it is how it is!
The (expected) opposite-effect is even more counterintuitive: when you start high-passing the lowest harmonics, eliminating the H2 does not matter at all:
In 1843, Seebeck made the unexpected observation that the perceived fundamental pitch is not affected when the first harmonic is removed from a spectrum
(1843 is much older than expected, this stuff seems to go back to
Helmholtz, the granddaddy of all Hs)
Apparently, the H-elimination does not matter much up to the ~4th, then it starts to go down up to 10th and then it suddenly plummets to ~zero. Again, not because the 10+ Hs are too high/inaudible. Other studies used 50-100Hz fundamentals with same results:
even when components of a harmonic complex can be resolved at the periphery of both ears, pitch discrimination as an indication of pitch strength is still limited to about the 10th harmonic.
That 'strange' behavior is supposedly related to a concept of resolved/unresolved harmonics (unresolved != inaudible) and it all kinda revolves around a theory called Autocorrelation: a model for explaining the audibility of higher missingFs which has no upper limit of frequencies (no theoretical limit, practice might beg to differ). Really like that autocorrelation

but it's stuff for another post. Or happy googling...
That is a bit too much digressing, back to the main Q. The short(ish) answers are:
- 2 Hs are not enough to prove anything.
- 3 Hs could be enough to prove a positive (i.e. it's audible). But not even close to enough for "not audible".
- The whole "dominance region for pitch" (i.e. 4-5 harmonics) is used as the utmost minimum by pretty much everyone and every missingF study. Even for studies involving easily audible Hs/missingFs. For a "not audible" conclusion we need (at the very least) the same "utmost minimum".
Oh well, that might be the most unpopular answer ever.
It is however pretty clearly stated in the OP that the "how many Qs" question needs an answer first. It is also hinted that this test might be impossible (particularly at 15kHz). A few initial comments also classified this test between hard and impossible.
That does not mean that I want to take the "easy way out" and declare the test impossible. I'd very much like to find a way forward and to keep the bet. Suggestions highly welcome.
P.S.
@ctrl @GXAlan & many others who helped. The above text kind of answers your posts too. Wish I had a (much) better answer, sorry for that. I can only hope that you agree with the "3 Hs is not enough" conclusion, that "dominance region for pitch" is not exactly my invention.
P.S2.
Writing this kind of giant posts is a serious pita. I am ~done for 'today' and will be out 'a while'..