On Sun, 14 May 2006 21:37:15 -0400, axolotl
wrote:

Larry Jaques wrote:

Hey, maybe I can focus a large parabolic mirror so his yelps will go
back at the owner's house, FINALLY making him hear the damned things.


Welll.. There have been some systems made using two ultrasonic sources,
one modulated, so that the mixed product where the beams cross is in the
audio range. You could have Elvis or space aliens tell him (and only
him, this would not work in a large area) to shut the &^%%! dog up.

Yup! This is a way to focus and localize audio-frequency sound
because the lower frequency is actually produced at the distant spot
by mixing of the ultrasonic energy from the two beams in the distant
region.

Sooo---you could produce a yapping dog (or yowling cat-in-heat,
copulating elephants, frantically-feeding hyenas or Wagner's "Ride
of the Valkyrie" ) right outside his bedroom window -- sweet dreams,
MF -- and he'd have one hell of a time figuring it out because the
sound level would diminish and be behind him as he approached your
boundary while moving away from the intersection region. Tawk
about deniability! Nothing to deny cuz nobody'd believe him.

"They're driving me nuts with the hyenas and elephants, I can't
sleep!" "Uh huh, and who might 'they' be, Sir?" "It's gotta be
that S.O.B. Larry Jaques over there."

Cop looks. "Over where?" "There, there, across the railroad
tracks." "Uh huh. Care to give us a urine sample, Sir?"