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It's the most promising audio advance in
years, and it's coming this fall: Hypersonic speakers, from
American Technology (headed by the irrepressible Woody Norris,
whose radical personal flying machine appeared on our August
cover), focus sound in a tight beam, much like a laser focuses
light. The technology was first demonstrated to Popular
Science five years ago ("Best of What's New," Dec. '97), but
high levels of distortion and low volume kept it in R&D
labs. When it rolls out in Coke machines and other products
over the next few months, audio quality will rival that of
compact discs.
The applications are many, from
targeted advertising to virtual rear-channel speakers. The key
is frequency: The ultrasonic speakers create sound at more
than 20,000 cycles per second, a rate high enough to keep in a
focused beam and beyond the range of human hearing. As the
waves disperse, properties of the air cause them to break into
three additional frequencies, one of which you can hear. This
sonic frequency gets trapped within the other three, so it
stays within the ultrasonic cone to create directional audio.
Step into the beam and you hear the sound as if it
were being generated inside your head. Reflect it off a
surface and it sounds like it originated there. At 30,000
cycles, the sound can travel 150 yards without any distortion
or loss of volume. Here's a look at a few of the first
applications.
1. Virtual Home Theater
How
about 3.1-speaker Dolby Digital sound? With hypersonic, you
can eliminate the rear speakers in a 5.1 setup. Instead, you
create virtual speakers on the back wall.
2.
Targeted Advertising
"Get $1 off your next purchase of
Wheaties," you might hear at the supermarket. Take a step to
the right, and a different voice hawks Crunch Berries.
3. Sound Bullets
Jack the sound level up to
145 decibels, or 50 times the human threshold of pain, and an
offshoot of hypersonic sound technology becomes a nonlethal
weapon.
4. Moving Movie voices
For
heightened realism, an array of directional speakers could
follow actors as they walk across the silver screen, the sound
shifting subtly as they turn their heads.
5.
Pointed Messages
"You're out too far," a lifeguard
could yell into his hypersonic megaphone, disturbing none of
the bathing beauties nearby.
6. Discreet
Speakerphone
With its adjustable reach, a hypersonic
speakerphone wouldn't disturb your cube neighbors.
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