The main patent appears to have been back in 1999. Is anybody currently working with this sort of transducer for audio reproduction?
white paper
patent
white paper
patent
Hmm, I just realized that at least some of the odd little audio beam devices that have been hyped for advertising purposes for years now work this way, or at least some of them do. I thought those were just a phase trick (I mean an audible-range phase trick, like LRAD speakers, and they apparently have the patent for these... confusing).
So it works enough to sell commercial speakers.. how well can it work? The white paper certainly makes some enthusiastic claims. Can you just attach a waveguide to a transducer like this without spoiling the heterodyne effect? What kind of output are we talking about (enough to spread out the output)? The holosonics ones only get to 85dB, but they have no reason to be louder for their marketed purpose so... Distortion?
So it works enough to sell commercial speakers.. how well can it work? The white paper certainly makes some enthusiastic claims. Can you just attach a waveguide to a transducer like this without spoiling the heterodyne effect? What kind of output are we talking about (enough to spread out the output)? The holosonics ones only get to 85dB, but they have no reason to be louder for their marketed purpose so... Distortion?
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One of my favorite subjects
The LRAD isn't a phase trick per se but a phase array tweeter and functions just like a phase array antenna.
The hetrodyne effect is placing two independent beams where they are modulated differentially and once you enter the beams ( it's cross section) you can hear that audio modulation
The LRAD isn't a phase trick per se but a phase array tweeter and functions just like a phase array antenna.
The hetrodyne effect is placing two independent beams where they are modulated differentially and once you enter the beams ( it's cross section) you can hear that audio modulation
I found out a bunch of stuff about this since I posted it here. It seems like maybe distortion is problem and part of the solution is to lower the ultrasonic frequencies a bit, which limits the safe output, but real world data is scarce online. Far as I can find, Holosonics is the only retail(ish) product out there, and it's expensive, made-to-order, and relatively secretive on the capabilities, and LRAD isn't doing anything with it. There are some conspiracy folks that like to talk about driving people insane and/or hypnotizing them, but I'm not particularly interested in that...
There's a wiki page that makes a decent starting point for anybody that wants to look into this. I somehow failed to find it when I first came across this concept: Sound from ultrasound - Wikipedia, the free encyclopedia
There's a wiki page that makes a decent starting point for anybody that wants to look into this. I somehow failed to find it when I first came across this concept: Sound from ultrasound - Wikipedia, the free encyclopedia
tomato/tomato? Doesn't matter, we know what that can do, this is about the ultrasonic heterodyne concept. Thanks for posting. I was a little surprised nobody was interested at all. It may be a dead end for serious hifi, but still seems pretty interesting to me.
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If one used 2 LRADs they could be placed on a fixed structure like the wall of a building. Without the need to physically direct the ultrasonic beam, one would be able to cover a vast area off axis ± 30° by sweeping the phase to that coordinate.
Example of use would be the ability to message a single person in a crowd without others hearing that message. Or force a mob out of an area, while having the ability to give instructions without disturbing anyone outside the area of coverage. Inform potential customers of a sale or promotions as they window shop at the mall without disturbing anyone in the corridor or the businesses either side for you. I can go on and on with the applications this has.
No they are not the same but it's only with what and how you combine that makes this possible.
BTW one of my personal favorite applications of this would be theft control. Security watches over monitors a theft in progress, direct the beams to said thief and whisper, Oh you are so busted, saw that stack of DVD's you put up your dress. You are surrounded and the doors are locked! There is no escape! Please turn around and speak quietly to the officer on you left. Have a nice day in jail and thank you for shopping at...
Example of use would be the ability to message a single person in a crowd without others hearing that message. Or force a mob out of an area, while having the ability to give instructions without disturbing anyone outside the area of coverage. Inform potential customers of a sale or promotions as they window shop at the mall without disturbing anyone in the corridor or the businesses either side for you. I can go on and on with the applications this has.
No they are not the same but it's only with what and how you combine that makes this possible.
BTW one of my personal favorite applications of this would be theft control. Security watches over monitors a theft in progress, direct the beams to said thief and whisper, Oh you are so busted, saw that stack of DVD's you put up your dress. You are surrounded and the doors are locked! There is no escape! Please turn around and speak quietly to the officer on you left. Have a nice day in jail and thank you for shopping at...
Gootee,
I wouldn't go that far. There will be distortion, reflection which does cause interference and phase issues that cause issue. If one could take a MS Kinect for positional control what you are saying is correct, but with one caveat, would only work for one person at best and only if they maintain a head postition that is directed towards the speaker due to HRTF combined with a "dead end" room.
When we narrow the bandwidth to only support voice speech 300-3k then there is less issue (distortion), but be assured there are hard limitations to the concept to work properly.
Best situation is use outside where we have minimal reflections from nearby objects. Indoors and especially home use would be the worst scenario.
I wouldn't go that far. There will be distortion, reflection which does cause interference and phase issues that cause issue. If one could take a MS Kinect for positional control what you are saying is correct, but with one caveat, would only work for one person at best and only if they maintain a head postition that is directed towards the speaker due to HRTF combined with a "dead end" room.
When we narrow the bandwidth to only support voice speech 300-3k then there is less issue (distortion), but be assured there are hard limitations to the concept to work properly.
Best situation is use outside where we have minimal reflections from nearby objects. Indoors and especially home use would be the worst scenario.
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I've been reading the white paper and it's very interesting.
The author makes the claim that he can achieve 10% efficiency in air at 200khz with a piezoelectric loudspeaker. However he is not specific about how it can be done.
Piezoelectric transducers that can achieve 200khz have been available for many decades, but I have only seen them used in water for ultrasonic inspection and medical imaging. These transducers have a high output impedance and need water to transfer power efficiently, they don't work as a loudspeaker in air. I'm not saying that it's impossible to build a speaker that efficiently can play a 200khz sine wave, but I haven't seen one.
The author makes the claim that he can achieve 10% efficiency in air at 200khz with a piezoelectric loudspeaker. However he is not specific about how it can be done.
Piezoelectric transducers that can achieve 200khz have been available for many decades, but I have only seen them used in water for ultrasonic inspection and medical imaging. These transducers have a high output impedance and need water to transfer power efficiently, they don't work as a loudspeaker in air. I'm not saying that it's impossible to build a speaker that efficiently can play a 200khz sine wave, but I haven't seen one.
So what about lower frequencies, for better efficiency?
Hmmm... Small animals' hearing range... phased arrays... machine vision with automatic target detection, recognition, acquisition, and tracking... increasing SPL as a stray dog or cat gets farther inside your property line. Might also be interesting for human intruders. And it would be great for calling the kids for dinner, or messaging family members who are out in the yard.
I would like a wearable one, so that I could "whisper in the ear" of anyone in the room (or maybe send them text-to-speech audio).
What small animals are you guys talking about? I think the Holosonics one was 160kHz or somewhere around there (I can't seem to find where I read that now), which is lower than 200kHz, but not much of anything can hear that, just possibly some exceptional bats and insects, AFAIK. It is extremely loud, though, and there are safety concerns about it. Holosonics seemed to be intentionally limiting theirs to 145dB or so (another number I can't seem to find, rrrrgh).
What I had imagined for indoor use was two beams directed at a specially-shaped diffuser/deflector/waveguide to redirect it into a desireable and precise dispersion pattern. I am basically assuming someone better at physics than I could invent that.
What I had imagined for indoor use was two beams directed at a specially-shaped diffuser/deflector/waveguide to redirect it into a desireable and precise dispersion pattern. I am basically assuming someone better at physics than I could invent that
.What small animals are you guys talking about? I think the Holosonics one was 160kHz or somewhere around there (I can't seem to find where I read that now), which is lower than 200kHz, but not much of anything can hear that, just possibly some exceptional bats and insects, AFAIK. It is extremely loud, though, and there are safety concerns about it. Holosonics seemed to be intentionally limiting theirs to 145dB or so (another number I can't seem to find, rrrrgh).
What I had imagined for indoor use was two beams directed at a specially-shaped diffuser/deflector/waveguide to redirect it into a desireable and precise dispersion pattern. I am basically assuming someone better at physics than I could invent that
Is this it?
LRAD Corporation - PRODUCT OVERVIEW
LRAD is catered to the military and government agencies only. You won't see them at CES ...seem to be missing the point. Why did you mention LRAD in the first place if you cannot grasp the application?
As I said earlier, if you were to combine both technologies this is what can be done. Yes LRAD is a lower ultrasonic, why couldn't this be scaled to a higher frequency? It's done every day at RF and optical wavelengths. Other than acoustic coupling of air at these frequencies, being the main issue and is the biggest tech hurdle to overcome. Otherwise only lower level short range use is possible. Which I may add may not be all that bad of a thing depending on application
With most any driver, configured in a phase array this can be done (Think how big a 16Hz wave is... within reason people Also think of a variable directivity pattern without physically changing any other parameter within a given design.
Why you don't see this at the consumer or prosumer level is R&D cost. There simply isn't much of a market for something so complex and costs in the millions and may not work for your target market once developed. The limited success of the NAH is a perfect example.
Back in '99 Norris was making all kinds of claims, hitting the auto industry hard. Many bit, all turned away. Output level was so low that for an auto enviroment the road/wind noise often masked it and if you want to crank that one song up, forget about it. Who wants a radio like that?
...seem to be missing the point. Why did you mention LRAD in the first place if you cannot grasp the application?As I said earlier, if you were to combine both technologies this is what can be done. Yes LRAD is a lower ultrasonic, why couldn't this be scaled to a higher frequency? It's done every day at RF and optical wavelengths. Other than acoustic coupling of air at these frequencies, being the main issue and is the biggest tech hurdle to overcome. Otherwise only lower level short range use is possible. Which I may add may not be all that bad of a thing depending on application
With most any driver, configured in a phase array this can be done (Think how big a 16Hz wave is... within reason people
Also think of a variable directivity pattern without physically changing any other parameter within a given design.Why you don't see this at the consumer or prosumer level is R&D cost. There simply isn't much of a market for something so complex and costs in the millions and may not work for your target market once developed. The limited success of the NAH is a perfect example.
Back in '99 Norris was making all kinds of claims, hitting the auto industry hard. Many bit, all turned away. Output level was so low that for an auto enviroment the road/wind noise often masked it and if you want to crank that one song up, forget about it. Who wants a radio like that?
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and what animals can hear at these extreme frequencies you ask?
Perhaps the answer to that is in reading this pdf on AM. I just happened to stumble upon this in order to address this Q.
Google search results.
BTW it is a good read that does apply to the understanding of NAH
Perhaps the answer to that is in reading this pdf on AM. I just happened to stumble upon this in order to address this Q.
Google search results.
BTW it is a good read that does apply to the understanding of NAH
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