On Tue, 10 Mar 2015 13:15:43 +0000 (GMT), Jim Lesurf
wrote:

In article , Sumatriptan
wrote:
On 09/03/2015 20:49, Trevor Wilson wrote:


MORAL: With sufficient intensity, human hearing can extend way past
20kHz.


I wouldn't exactly call the sensation of a high level 20 kHz tone
'hearing' more like 'detection'. My normal hearing barely extends to
9-10 kHz these days but I was aware of an odd clicking sensation (best
way I can describe it) in an a relatives garden. Turned out to be a cat
repellent gadget. Sensation vanished when it was switched off.

I've also been aware of a vaguely uncomfortable feeling standing close
to a shop window that had some sort of 'anti-teen' sound device
installed. Couldn't hear anything at all...just an awareness of
something unpleasant. And I'm no teen.


FWIW Oohashi and others published research papers some years ago which
reported doing things like brain scans whilst people listened to sound
with/without and 'ultrasonic' portion.

Played by itself, people couldn't hear the 'ultrasound'. But their
brainscans were different with/without it when the main music was played.

So it seems possible that high frequency tones which are - in isolation -
'inaudible' may affect our perception when they accompany clearly audible
lower frequency sounds.

This isn't particularly surprising if true since human hearing physiology
is known to be highly nonlinear.

What it means for listening to music is harder to say. But it does make it
plausible that there *might* be some advantage in having bandwidths above
20kHz even when you can't hear isolated tones at that frequency, at least
in some cases.

Jim

I think a likely explanation is the simple non-linearity of the ear
causing audible intermod products when the ultrasonics were on.

d