This old Caltech paper reminds me of the older Oohashi paper that deals with the same subject (which I couldn’t find on the web anymore!). As you may know, in this day and age, digital audio is brick-walled at around 20kHz, since we believe that the human ear is incapable of hearing above this frequency, and thus there is no use to include this information in the audio signal (unless you are recording for bats or dogs). That is why no matter what sample rate is used for any audio project, like with the prevalence of 96kHz today, we never get to hear any audio information above 20kHz during reproduction. (Well, I simplified too much. I also need to mention that very few microphones and speakers go beyond 20kHz. And analog tape can certainly record higher frequencies.)

The paper says, “A discussion of the significance of these results describes others’ work on perception of air- and bone-conducted ultrasound; and points out that even if ultrasound be taken as having no effect on perception of live sound, yet its presence may still pose a problem to the audio equipment designer and recording engineer.”

There’s actually a lot of hot debate going on regarding the benefits of high-sampling rates for recording audio, and also a lot of marketing bullsh*t for new products that are capable of recording at such frequencies. But really, higher is not better, and Dan Lavry tells you why. The old Oohashi paper actually concluded that while audio is surely inaudible beyond 20kHz, the ultrasonic frequencies trigger some electrical brain activity in the listener’s head that changes the overall listening perception, or something along those  lines if I remember correctly.

Here’s the link to the Caltech paper… http://www.cco.caltech.edu/~boyk/spectra/spectra.htm. Have a read if this interests you.

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