Good vibrations

In the course of research into ultrasonic frequencies in recorded music I came across some erudite papers that suggest we don't so much hear these as feel them. Apparently some instruments do produce such frequencies - cymbals for instance - and althouth the eardrum is virtually motionless at near 20 kHz these ultrasonics actually set up vibrations in the brain.

It seems this has been proved in controlled tests n a live music environment but for these frequencies to be audible in recordings engineers would need to use highly sophisticated microphones and extremely high sampling rates.

The upshot is that listening is a much more complex physiological process than we might imagine, and that numbers don't always tell the full story (as Kirk's listening test so clearly demonstrated).