Yeah, this is more about the amount of ultrasonic content present in instruments. Nobodies doubting that these high frequencies are around us all the time, just that we can't hear/sense them. In comparison, radio waves are going through us right now but we can't see them.
And as it also says in your study, the next step would be to measure at normal listening distances. Remember that air absorbs high frequencies more than low frequencies.
Lastly, as i already said, digital audio won't play anything past 22.1khz, unless you get into higher sampling rates. But most of us listen on cd or mp3.
In the part about hearing, they're referring to the same study that you posted earlier:
X. Significance of the results
Given the existence of musical-instrument energy above 20 kilohertz, it is natural to ask whether the energy matters to human perception or music recording. The common view is that energy above 20 kHz does not matter, but AES preprint 3207 by Oohashi et al. claims that reproduced sound above 26 kHz "induces activation of alpha-EEG (electroencephalogram) rhythms that persist in the absence of high frequency stimulation, and can affect perception of sound quality."
The fact is, the mechanical limits of our ears prevent us from hearing ultrasonic frequencies. From your article:
In a paper published in Science, Lenhardt et al. report that "bone-conducted ultrasonic hearing has been found capable of supporting frequency discrimination and speech detection in normal, older hearing-impaired, and profoundly deaf human subjects."
This is from another
article:
The upper frequency limit in humans (approximately 20 kHz) is due to limitations of the middle ear, which acts as a low-pass filter. Ultrasonic hearing can occur if ultrasound is fed directly into the skull bone and reaches the cochlea through bone conduction without passing through the middle ear.
So the only scientifically proven way to hear ultrasound is if its fed directly to your skull. But it certainly can't be conducted via air through your ears, that's just not possible. And seeing as how most of us don't have an ultrasound device attached to our skull, i'd say that the current studies are fairly conclusive.
