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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!"
One step closer to the cone of silence!
Damn. I'm still grappling with the unmistakable cone of ignorance
standing right next to someone and they would hear nothing
That would be great if someone could rig my wife up with one of these... the silence would be bliss! :)
At last - high volume p0rn without waking up my girlfriend!!!
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.
"We are focused on achieving high volume applications featuring the unique benefits of HSS directed sound. --"To the Shareholders of American Technology Corp." Business Wire, March 25, 2002
I saw a TV programme about this a while ago.
One of the guys who was developing it enjoyed pointing it down towards people on the street and speaking to them. He said they got really creeped out and started looking around to see if anyone else heard it.
I think it'd be more fun to involve two people and two speakers. Have a sort of devil and angel think going on.
"Kill that guy over there!"
"No, don't do it"
"Go on, don't listen to that pussy!"
from here and here.
i'm sure this'll come around again in the next few months...
I'll turn into a supernova and burn up everything. Well I'll turn into a black little hole and you'll turn into string.
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'!!
I don't know what the official definition of vapourware is, but I have seen this in use from rooftops at MIT (it's fun to see the reaction of people as they try and figure out if anyone else heard that voice), and am helping in the development of a line of products that use these speakers as a key component.
I think the reason you probably haven't seen it yet is that there aren't many finished products made yet, and part of that might have to do with the fact that lots of local bylaws seem concerned with this kind of thing (they liken it to talking on cell phones while driving).
It won't be long before this is everywhere. I think the tech is just slightly outpacing the market right now.
The world's only surviving livewriter.
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!
Based on this it seemed to be pretty far advanced (and that was two years ago). Granted I've yet to see it being used commercially.
Tab books published instructions how to build a device that does exactly this decades ago... TAB!
Yeah, I know the cover looks ridiculous... I bought it when I was a teen and still have it - neat projects inside and better written than the cover would indicate.
- Preferences: Solaris 10 (servers), Ubuntu (desktops), Solaris 11 (personal servers) -
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
It would be simple to defeat though. The effect relies on heterodyning a signal (mixing HF to produce an intermodulation effect) so broadcasting white noise above the range of hearing should drown the wanted signal nicely - just like interference on an AM radio. Say a small device located near the billboard - or two piezo drivers on the outside of headphones, heck you could build it into your cellphone hands-free kit.
Done well, you wouldn't hear a thing; even partial cancellation should reduce the adspeak into something akin to a distant ocean sound.
I think there would be privacy isues to overcome on the part of the Admen first however - remember the hoo-haa over subliminal advertising?
"This is the lord, your god. I have decreed that you may save 15% or more on your car insurance by switching to Geico!"
I don't suffer from insanity, I enjoy every minute of it!
You could be standing right next to someone and they would hear nothing.
That's the idea, but in reality it works a tad different. Wherever the beam hits sort of becomes the apparent source of the sound. So if you aim it at someone, they'll hear it quite clearly - more so than everyone else - but the sound will now appear to be coming from them. Quieter, but still apparent.
I've got 2 of the HSS units right here, and though they're super-cool for messing with people, (See other posts) they've got some drawbacks.
1) There's no bass, treble only.
2) The units we have come with a rather noisy cooling fan.
3) They clip quite easily - you have to watch your volume levels.
4) They're not terribly reliable. I've seen them in a few labs I've worked in or with, and we all seem to have the same issues.
Overall a cool product, especially for the gee-whiz factory, but certainly not ready for practical use just yet.