Audio's Next Big Thing?

[Gservo]

TARGETED SOUND
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.

Illustrations by Stephen Rountree






We've heard hypersonic sound. It could change everything.

by Suzanne Kantra Kirschner




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.

[mackerel]

I'd be interested to see how thy actually implement this. I've heard about earlier work on this, which seems to work but using multiple ultrasonic sources which create a beating at a point. Trouble is, how do you get it to demodulate and produce a sound we can hear?

[jema]

I'll have to hear this one to believe it!

Would be quite incredible if it works in a practical sense.

jema

[CyberdynSystems]

In the proffesional audio world, the latest rave are "Line Arrays" or "Linear Arrays", though not quite as focused as "Hypersonic" claims to be, they are extremely tightly focused. In my own theatre, I have sat in a sweet spot in the audience 60 feet (20 meters) from a great sounding line array speaker, only to stand up and the sound is almost gone! The 2.5 foot difference in height took me out of the focus point!

The Pioneer of linear arrays is a French company called, "L'accoustics" (great grasp of the language eh?) who came out with a system called V-dosc in 1993. Since then all the heavy hitters have played catch up, like Meywrs, EAW, EV, etc....

http://www.l-acoustics.com/
and Meyers has some too...
http://www.meyersound.com/mseries/m3...ray_theory.htm
http://www.kerrville-music.com/jacobsaudio/whyline.htm

I am concerned about Americans technologies use of the terms "Ultrasonic" and "Hypersonic" both of wich would mean, frequencies that the human ear can not hear........

[prokaryote]

Originally posted by mackerel
I'd be interested to see how thy actually implement this. I've heard about earlier work on this, which seems to work but using multiple ultrasonic sources which create a beating at a point. Trouble is, how do you get it to demodulate and produce a sound we can hear?

I think that you may have answered your own question here. Interference causes a waveform that the ear can pick up. Think of adding several sinusoidal waveforms of high frequency that produce a resultant sinusoidal waveform of much less frequency. That's how and why Fourier transforms work, but in reverse.

prok.

[mackerel]

Although a mathematical lower frequency signal can be produced by beating ultrasonic waves, you still can't hear it directly! The fundamental is still above our hearing range, and the lower frequency signal needs to be demodulated to be heard. To demodulate, you'll need a non-linear load. If a typical house wall is one of these or not I don't know.

[jema]

Originally posted by CyberdynSystems
In the proffesional audio world, the latest rave are "Line Arrays" or "Linear Arrays", though not quite as focused as "Hypersonic" claims to be, they are extremely tightly focused. In my own theatre, I have sat in a sweet spot in the audience 60 feet (20 meters) from a great sounding line array speaker, only to stand up and the sound is almost gone! The 2.5 foot difference in height took me out of the focus point!

The Pioneer of linear arrays is a French company called, "L'accoustics" (great grasp of the language eh?) who came out with a system called V-dosc in 1993. Since then all the heavy hitters have played catch up, like Meywrs, EAW, EV, etc....

http://www.l-acoustics.com/
and Meyers has some too...
http://www.meyersound.com/mseries/m3...ray_theory.htm
http://www.kerrville-music.com/jacobsaudio/whyline.htm

I am concerned about Americans technologies use of the terms "Ultrasonic" and "Hypersonic" both of wich would mean, frequencies that the human ear can not hear........

Great links Makes me wonder if this stuff will be a long time before it is available for home use though?

jema

[prokaryote]

Originally posted by mackerel
Although a mathematical lower frequency signal can be produced by beating ultrasonic waves, you still can't hear it directly! The fundamental is still above our hearing range, and the lower frequency signal needs to be demodulated to be heard. To demodulate, you'll need a non-linear load. If a typical house wall is one of these or not I don't know.

Granted, I think that the ear does that for you as would probably the walls or any other physical sensor. Couldn't the inertia and hysteresis response of the physical elements that make up the ear respond dynamically to the waveform "traced out" by the amplitude peaks, but not respond dynamically to a constant amplitude high frequency sound? I'm thinking that ultra-sonic sound may actually cause a sensory hair to say flex but not allow it to unflex and reset so that another nerve pulse could be sent along (or that it does flex and unflex too fast to allow a reset of the nerve cell's ionic balance). The high frequency sound would act as if it were a constant pressure upon the hair. Now if the amplitude of the high frequency sound were to vary over time, then the hair would respond to the change in amplitude over time as if this were the actual frequency being heard. Just a hypothesis, could easily be tested I think.