Illustrations by Stephen Rountree

Unlike ordinary speakers, which disperse sound in all directions, American Technology’s speakers emit ultrasonic frequencies in a focused cone, like a flashlight. Only when you disrupt the sound beam or reflect it off a surface do you hear it. So audio can be pinpointed to reach an individual or widened to target a larger group.

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.