This process has nothing to do with ventriloquism. Actually, both
systems utilize two ultrasonic
carrier frequencies transmitted by a multiple series of output
transducers which, when combined, create
instantaneous sum and difference signals. The sum signal is discarded
while the difference signal is
transformed into the audio that is "beamed." Unfortunately, while the
concept is impressive (we have
a beta version of American Technology's =96 Norris' version that can
beam a signal about 400m in an absolute
straight line without attenuation over distance and so that only the
person at whom the beam is aimed
can hear the signal) =96 the systems do not work very well.
For one thing, the output is typically limited to signals between 500
- 6kHz. Second, the output level of the
two heterodyning carrier signals (125+dB) often causes those
sensitive to motion sickness (like my wife, for instance),
to experience nausea or dizziness while in the range of the beam or
output transducer. At one point in the process,
we thought of incorporating this technology into the public space
installations (zoos, aquaria, museums) we were
designing and installing. But because the systems caused obvious
stress in some humans and non-human animals,
we decided against them until the bugs were worked out. We know
because we were asked to write the "white
paper" for American Technologies and fortunately hedged our bets on
all seemingly positive statements we
were asked to write at the time.
Bernie Krause
On Oct 2, 2007, at 6:11 AM, Ray Mansell wrote:
> Syd Curtis wrote:
> > Would any Naturerecordist care to comment on ventriloquism in birds?
> >
> > I have encountered occasional references in the literature, but
> it seems to
> > me to be a physical impossibility. Am I right?
> >
> >
>
> While I have no idea whether or not birds or other creatures have this
> ability, nevertheless the technology does exist to create directed
> "beams" of sound which may well give the impression of ventriloquism.
> Search for references to Hypersonics (inventor- Woody Norris) or
> Holosonics (inventor - Joseph Pompei). Since the technology uses sound
> waves beyond the range of human hearing, and since we know some
> animals
> can generate such sounds, then perhaps ventriloquism *is* a
> reality. It
> would certainly be a fascinating subject for research!
>
> Ray Mansell
>
>
>
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