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Reply-To: "Daniel A. Thomas"
From: "Daniel A. Thomas"
Subject: Re: Coming soon to a theatre near you - endless mischief potential
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
Date: Sun, 13 Oct 2002 04:36:25 -0400
NNTP-Posting-Date: Sun, 13 Oct 2002 04:36:23 EDT
"John Woodgate" wrote in message
| I read in sci.electronics.design that John Larkin
) about 'Coming soon to a theatre near you - endless
| potential', on Sat, 12 Oct 2002:
| >I believe that eardrums are slightly nonlinear (I bet John W knows
| >something about this) so might serve as a mixer/detector for very
| >levels of two-tone ultrasonics.
| Not the eardrum in particular; the whole ear-brain system is
| - it has a logarithmic response to sound pressure.
| > But even 30 KHz is hard to make into a
| >tightly directional beam (as in the lifeguard example) and the
| >would certainly have to be high, certainly dangerous, to produce
| >a barely audible response.
| Well, probably but maybe not. You can hear 'beats' between two
| that how piano tuners do the tuning, and I suppose other string
| instruments are tuned in the same way. These beats are mostly
| variations as one tone swings in and out of phase with the other.
| one can actually hear a very fast beat as a tone - the difference-
| frequency intermodulation product produced by ear-brain
| >Besides, the invention claims that the
| >sonics are created in air, and that the sonics are somehow confined
| >the ultrasonics, and doesn't lose volume for 150 yards. Stupidity.
| Yes, that strains credulity too far. 30 kHz is rather rapidly
| attenuated, especially in dry air (RH of 20 to 30%).
| >Popular Science prints this sort of impossible crap all the time.
| It seems a futile exercise, to me.
| Regards, John Woodgate, OOO - Own Opinions Only.
| Interested in professional sound reinforcement and distribution?
Then go to
| PLEASE do NOT copy news posts to me by E-MAIL!
OT but an interesting experiment. You will need two audio signal
and a pair of stereo headphones. Feed one of the generator outputs to
the left ear and the other to the right ear. There outputs should be
in the audio spectrum and of the same amplitude. Do you hear two tones
at the generators frequency or do you hear something else?
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