In tandem with an ultrasonic emitter and a signal processor/amplifier, HSS projects a column of modulated ultrasonic frequencies into the air. The ultrasonic frequencies
are inaudible by themselves, but the interaction of the frequencies with the air create sounds that can be heard by anyone inside the column. Hypersonic sound can direct sound as precisely as a laser beam can direct light. One only needs to be standing in the path of an HSS beam in order to hear the sound. However, the sensation to those hearing is that the sound is being projected from inside their skull.
Pretty cool, thinks inventor Norris. Or pretty creepy if you don't know what's going on. It is already being done from a billboard on Prince Street in New York City. Advertising fora television show called "Paranormal State" which airs on the Arts and Entertainment Network (A&E), has been sent through HSS to unsuspecting pedestrians who trigger a sensor as they stroll by. The sound that is emitted can be heard only by them. Science and technology
writer Clive Thompson, has written about the Prince Street billboard for Wired magazine.
He experienced HSS himself, writing that it felt "creepy" to hear a woman's
voice whisper, "Who's there Who's there" It used to be that we could at least be guaranteed privacy in the space between our ears.
That is no longer true, thanks to the invention of "in-head advertising"
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The freedom to think our own thoughts without artificial manipulation from outside Share with your friends: 
