Re: Ultrasonic Hearing in Music Recording & Reproduction

[Pawel Kusmierek <p.kusmierek@xxxxxxxxxxxxx>]

> Does music contain ultrasonic information? James Boyk has shown that
there
> is
> such content (http://www.cco.caltech.edu/~boyk/spectra/spectra.htm).
>

But this may be useless information because listeners might be unable to
access it. In such case, there would be no point recording it.


> Does current recording practice encode such frequencies?  Well it
depends
> on the
> microphones and the music, but mostly not.  First of all, most of the
microphones that engineers love and cherish are large diaphragms that "do
> not
> go up there".

This is true, although several manufacturers offer microphones which go up
to 40 kHz or more. These include Earthworks, Sanken, Schoeps, and
Sennheiser.


 Secondly, lots of the processing gear that is currently in
> use
> "does not go up there", particularly digital equipment, although this is
changing.

Digital equipment which records at 24/96 is easily available, and some can
use 192kHz. Digital processing is usually done in a computer, which does
not care about sampling ferquency used. I think that it's harder to get a
proper mic rather than equipment.

> And of course, the large majority of people are listening on
> reproduction systems, and using media, which "do not go up there".

Yes, but SACD and DVD-A, which slowly gain popularity, are capable of
going beyond 20 kHz, and, as said by Rob Maher, speaker manufacturers
continue introducing products with frequency range up to 40-50 kHz.

So there are means to record/playback in the low ultrasonic range, but
this of course does not prove that it is necessary or beneficial. In only
shows how well do the marketing departments work.
It is also somewhat doubtful if these technologies will gain wide
popularity. Most people are happy with 128 kbps mp3's which carry nothing
above 16 kHz. Still, aggresive marketing can do miracles.

> One paper that is cited add nauseum in the "for high-resolution"
literature as a
> scientific justification is:
> http://jn.physiology.org/cgi/content/abstract/83/6/3548
>
> I have not seen these results repeated (help list!).

Yes, please someone replicate this...

Pawel

-- 
Pawel Kusmierek PhD
Department of Physiology and Biophysics
Georgetown University Medical Center
The Research Building WP23
3970 Reservoir Road NW
Washington, DC 20007
phone: +1 202 687-8842