Jesper Magnusson Posted November 16, 2012 Report Share Posted November 16, 2012 Thought I'd post this up for discussion as I just found out about it, and didn't find any reference to it on this site. Something that appears to have a longer research history, but the inventor Woody Norris has developed something he calles "hypersonic sound". These are devices that uses the higher directionality of ultrasonic frequencies to create speakers with similar qualities. A modulated ultrasound signal is transmitted, which uses the nonlinear properties of air to make the air itself act as a demodulator. A highly directive beam of ultrasonic sound therefore causes a sound signal to be created in the air it passes through. The video is the inventor giving a demonstration and talking about the usages on a Ted conference. You never hear the demonstration, but apparantly the audience he directs it towards does. I don't quite understand how this works to allow for higher directionality, since a sound, even if it's made as he says "by your ears", should still continue to spread from that point and not be directional in itself. Maybe the demodulation happens in a way that also makes the sound propagate in the same direction as the modulated signal, or that the beam is precise enough to allow the sound level created to so low that it wont pose a problem (since it's created so close to the ears). If this actually works, and the technology becomes widely used and refined (as of now, it doesn't allow low frequencies, and we don't know about the quality), it could mean a change in how sound is emitted and experienced. True stereo can be created where each ear cannot hear more than one channel (effectively headphones without the cans). Concerts where the sound level is equal everywhere, and movie theaters that doesn't have sweet spots. For movie work, actors can be played music, ques or lines on set that is not picked up by the microphones. Maybe sometime in the future the technology can be used to create extremely directional microphones, that somehow measure the nonlinearity in the air before it that is created by the sound waves, and that data is then modulated into the represented sound signal. Quote Link to comment Share on other sites More sharing options...
soundslikejustin Posted November 16, 2012 Report Share Posted November 16, 2012 Sennheiser tried it. They called it Audio Beam. The project was abandoned. It's now the LRAD system used in the military. Quote Link to comment Share on other sites More sharing options...
Jesper Magnusson Posted November 16, 2012 Author Report Share Posted November 16, 2012 Thanks, I'm always fascinated by new (for me anyway) discoveries in sound and was probably a bit fast in making a post about it. I made another search with different keywords and this time I was able to find more about it. I still think it's an interesting subject, though there are a number of walls that may not be possible to overcome. Quote Link to comment Share on other sites More sharing options...
Jay Rose Posted November 16, 2012 Report Share Posted November 16, 2012 I don't quite understand how this works to allow for higher directionality... Shorter wavelength means more directivity. Haven't you noticed that HF whistles (say, the flyback sound from a CRT) are very directional? You might hear them in one part of a room, but not if you move a couple of feet away. (That's also how you can tell if it's really a HF whistle you're hearing, or tinnitus: Move your head. If the sound doesn't change, it's coming from your own nervous system.) ...even if it's made as he says "by your ears", should still continue to spread from that point and not be directional in itself. But it'll be at a much lower level, just loud enough for the nearby eardrum. Not particularly directional, but inverse-square means others won't hear it. Quote Link to comment Share on other sites More sharing options...
LarryF Posted November 16, 2012 Report Share Posted November 16, 2012 http://en.wikipedia.org/wiki/Hypersonic_sound Pretty complete article in Wikipedia. Skip past the math. This technology has been around for some time and has been next year's great sound breakthrough for a decade. Safety, distortion and cost have held it back. The last great application was for targeted advertising in shopping malls, etc. Just what we need. Larry F Quote Link to comment Share on other sites More sharing options...
Jesper Magnusson Posted November 16, 2012 Author Report Share Posted November 16, 2012 This technology has been around for some time and has been next year's great sound breakthrough for a decade I found the wikipedia link after searching on the sennheiser product line as mentioned by soundslikejustin. I'm sorry to bring up old news - I'll do my homework better in the future. Shorter wavelength means more directivity What I meant was how it affected directivity once the audible sound has been created. It projects ultrasonic sound in a very directive beam, and then audible sound waves with longer wavelengths are created along it's trajectory. But once the "normal" sound waves are made, unless I'm missing something, I assume they would spread from that point in a non-directive way. Hence my enquiry. As a fun sidenote - my tinnitus is actually very dependant on strains and muscles in my neck, so sometimes when I turn my head the tinnitus changes... Quote Link to comment Share on other sites More sharing options...
LarryF Posted November 16, 2012 Report Share Posted November 16, 2012 I found the wikipedia link after searching on the sennheiser product line as mentioned by soundslikejustin. I'm sorry to bring up old news - I'll do my homework better in the future. Hi Jesper, I did not intend to come off as putting down your inquiry. Sorry, if I seemed critical. If every question here was only about new shiny things, few would have any answers. My only intent was to say that though "hypersonic sound" seems like a great thing, after many years it has still not proven marketable even after lots of effort by some well funded companies. Therefore, it may very well be a dead end. Best Regards, Larry Fisher Quote Link to comment Share on other sites More sharing options...
daniel Posted November 17, 2012 Report Share Posted November 17, 2012 http://en.wikipedia....ypersonic_sound Pretty complete article in Wikipedia. Skip past the math. This technology has been around for some time and has been next year's great sound breakthrough for a decade. Safety, distortion and cost have held it back. The last great application was for targeted advertising in shopping malls, etc. Just what we need. Larry F http://www.holosonics.com/ are we hearing voices in our heads or is something else going on? Quote Link to comment Share on other sites More sharing options...
Jesper Magnusson Posted November 17, 2012 Author Report Share Posted November 17, 2012 Larry, I didn't take offense at all - sorry it came out that way! I'm thankful for your input, and was just trying to offer an excuse for my lack of research. Well, thanks to all here I'm a bit wiser, and I still hope for a breakthrough in this area! Quote Link to comment Share on other sites More sharing options...
hobbiesodd Posted November 18, 2012 Report Share Posted November 18, 2012 If you're really interested, build your own: http://www.lucidscience.com/pro-laser%20spy%20device-1.aspx Quote Link to comment Share on other sites More sharing options...
Jesper Magnusson Posted November 18, 2012 Author Report Share Posted November 18, 2012 http://www.lucidscie...y device-1.aspx I have to say, that's a pretty cool concept that was also unfamiliar to me - thanks! You gotta love the internet and DIY! Quote Link to comment Share on other sites More sharing options...
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