[Cryptography] NIST Workshop on Elliptic Curve Cryptography Standards

[Tom Mitchell]

On Thu, May 21, 2015 at 4:58 PM, Ray Dillinger <bear at sonic.net> wrote:
>
> On 05/21/2015 01:25 PM, Arnold Reinhold wrote:
> > True story: A friend of mine was working on having PCs communicate
> across air gaps using ultrasound. He was testing out his implementation of
> the concept when his kids came home and said “Dad, that’s really loud.”
> Lends a whole new purpose to take your kids to work day.
> >
>
> Well-known fact to pediatricians and family-practice doctors,
> but relatively unknown to the general public.  Adults hear up to
> about 20 KHz.  .....They can often hear sounds in the 30 KHz range.
>
>
Played with this a while back and found that inexpensive laptop
sound, speakers and microphones very much limit the the use
of ultrasonic sound.  My laptops had filters clamping -25Hz and +20KHz
to keep amplifiers and other hardware intact.   This extends to
the headphone jacks as well.

And yep I grew up with folk that could hear bats and dog whistles.
http://www.lsu.edu/deafness/HearingRange.html

But this does open a door to detector technology...
http://en.wikipedia.org/wiki/Bat_detector



-- 
  T o m    M i t c h e l l
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