HYPERSONIC SPEAKERS TARGET THE LISTENER
Wouldn't it be nice if you could target your loudspeaker system to
just the people who need to hear the message? Hypersonic speakers, due
out this fall, focus soundwaves in a tight beam, much like a laser
focuses light. The applications are myriad, from creating virtual
speakers that distribute sound around the room, to a speakerphone
system that only you can hear, to sound bullets that jack up the
decibel level to 50 times the human threshold of pain, giving law
enforcement officials a nonlethal alternative to conventional weapons.
The key is frequency: the ultrasonic speakers, made by American
Technology, create sound at more than 20,000 cycles per second, a rate
high enough to keep it focused in a beam and beyond the range of human
hearing. As the waves disperse, the properties of air cause them to
split into three additional frequencies, one of which is audible. Step
into the beam and you hear the sound as if it were being generated
inside your head. By bumping up the cycles to 30,000 per second, the
sound can travel 150 yards without any distortion or loss of volume.
(Popular Science)
http://www.popsci.com/popsci/science/article/0,12543,351353,00.html
Just an email away......
Justin


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