Slashdot Mirror
Directed Sound
yawningyellowyak writes "Technology Review has an interesting article on directed sound. Ultrasonic 'sound' is sent out from a 'speaker' and the distortion encountered on hitting the air produces hearable sound, but only in certain spots. You could be standing right next to someone and they would hear nothing.
One step closer to the cone of silence!"
And we think spam is bad...
But I doubt the car owners would want it. Why have a loud sound system in a car if the whole world can't hear (and know about) it.
Has anyone ever been into into the Lucas Sound Studio at MGM in Disney world? I believe it's co sponsored by AT&T.
* There's something similar to this. You put on headphones.
* You're in a booth about the size of a small 1/2 bathroom.
*It goes completely dark, but you are told to close your eyes for an even better effect.
You then proceed to "become a CEO" for a day of a Fortune 500 company - you get your hair cut and blowdried in the boardroom - you CAN FEEL the scissors and hear them close to your ears and atop your head. Then you can FEEL HEAT from the blowdryer - and it's nothing but sound rather an auditory/perceptual illusion.
Imagine if this could be done with the directory sound.
Yell & scream & rant & rave... it's no use... you need a shaaaave ~ Bugs Bunny
This kind of technology (although not as refined as mentioned in the article) has been in use for quite some time. For example, in Oslo Lufthavn (Oslo/Norway international airport) there are "quiet spots" where a speaker is used in combination with a parabole to create "sound spots" in the airport lounge area. The sound (sea waves, bird song, etc.) is basically only audible to the person standing directly under the speaker/parabole.
SIG: TAKE OFF EVERY 'CAPTAIN'!!
Linear transformations cannot create new frequencies, only alter the relative intensity of frequencies that already exist. If ultrasonic sound is being heard, some nonlinearity somewhere is converting it to audible sound.
The thing that I have to wonder about is that this kind of nonlinearity implies fairly high (ultrasonic) sound intensities, and suggests that stuff inside your head is being driven beyond its elastic limit. The big thing that seems to me to be missing from the article is any statement of the ultrasonic sound power level, in decibels, that is being delivered to your head (and the ratio between the actual ultrasonic sound level and the apparent audible sound level).
How does this compare, for example, to the sound levels used for ultrasonic imaging in medicine?
I'm not suggesting that the process is necessarily dangerous, but it isn't obvious that it's intrinsically safe, either. It's one thing to be subjected to high-power ultrasound a few dozen times during your lifetime for the purpose of preserving your health. It's quite another to be subjected to it day in and day out, for your convenience in listening to music, or for some advertiser's convenience in interrupting your train of thought.
"How to Do Nothing," kids activities, back in print!
FWIW, I saw this demonstrated on The Screensavers on TechTV a couple months ago. It seemed to work when they turned it on the studio audience. Only the people that the machine was pointed directly at could hear it. It could have been an elaborate hoax, but then again, so could the Moon Landing...
I just want to take over the world...Why does that automatically make me EVIL?
will dominate this market, because there is a new technique in acoustics that will eclipse the ultrasound method. Using something called time reversal, you can pinpoint the output of sound to a single location in 3 dimensional space, focusing around objects, people whatever; no beam, no drop off.
This focusing can be done with more than just sound waves however, and the first applications are in medicine, however, it does apply to sound as well.
The basic idea is that if you create a sound from some source location, and record all of the noise at another location, then play this noise signal backwards from the recorded location the sound will reappear in the one spot from which it was originally played. An analogy is that if you take a pool ball, put it right in front of a pocket, and then bounce it outwards really hard, letting it bounce against the walls multiple times, but noting the exact location of the last bounce of the ball, then if you reshot the ball at the exact spot where you last saw it bounce, it would go back in the whole.
-ashot
This system relies on non-linearities to produce different frequencies. It's the same principle that is used to transform radio frequencies into audio in a radio. The basic frequency transforming component is called a mixer. Usually mixers are quite lossy. ie. you have to put a lot more energy in than you get out. In this case they are using the air or part of my body as the mixer so I expect that this process is really lossy. So the first question is: "How much energy are they bombarding me with?"
Second: It is well known that ultrasonic energy at the right frequency produces a fear reaction in people. They are afraid but because they can't hear anything, they don't know why.
For sure I don't want anyone pointing one of those things at me until it is PROVEN safe.
What they wanted
was a sound that could kill someone from a distance
so they go ahead
and the meter's over in the red
it's a mistake in the making
The company producing the equipment is American Technology Corporation at http://www.atcsd.com/tl_hss.html According to their own site one test showed a level of 110 db at 2 metres at 48KHz giving an apparent audio level (3 KHz) of 95 db. The level at 16 metres was 80 db at 48 KHz and still 90 db at 3KHz. Apparently they are already installing them in soft drink dispensing machines in Tokyo. (We soon won't know who is schizophrenic and who isn't). Cheers
First commercial applications.... Ads. Right out of Minority Report.
....
John Anderton, you look like you need a
My wife went to an tech award show last year at which this product won something. The presentor mentioned that the pentagon was also interested in the product. He said that it is possible to turn the volume up to lethal levels.
Actually, this is already being implamented by the US Military in Iraq. It is used at checkpoints to speak to aproaching parties. And the Military has signed a new contract with American Technology for $1.1 million to deliver these LRAD's (long range acoustice divices) to the Marines. "LRAD is a breakthrough long-range hailing and warning, directed acoustic device that is designed to determine intent, change behavior, and support various rules of engagement. With LRAD, a sentry can issue a focused verbal challenge with instructions in excess of 300 hundred yards, and follow up with a warning tone to cause behavior change. Recorded messages can be selected and delivered over LRAD in multiple languages."[from an American Technology press release. regarding this contract] So far this is the biggest contract the company has and most likely, for years to come, the most lucrative applications will come from military applications, both as defense and as weapons. But ultimatly, comercial application will exceed the military in the technology's application and source of revenue for ATC.