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Old 11th July 2013, 01:43 PM   #1
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Default Norris Acoustical Heterodyne™ - What happened?

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
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Old 12th July 2013, 12:56 AM   #2
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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?

Last edited by dumptruck; 12th July 2013 at 12:58 AM.
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Old 20th July 2013, 03:02 AM   #3
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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
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Old 20th July 2013, 03:16 AM   #4
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Both concepts can be combined to enhance the control of the coverage area. That is if it were not for the bloody patent system

They are not new tech in any way, shape or form to some people
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Old 20th July 2013, 06:36 AM   #5
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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

Quote:
Originally Posted by Greebster View Post
The LRAD isn't a phase trick per se but a phase array tweeter and functions just like a phase array antenna.
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.

Last edited by dumptruck; 20th July 2013 at 06:48 AM.
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Old 20th July 2013, 01:59 PM   #6
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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...
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Old 20th July 2013, 03:15 PM   #7
gootee is offline gootee  United States
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Interesting. A hifi system could track your head position and orientation and deliver the correct phase and amplitude to each ear, eliminating room effects and other sound-field-related variations.
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Old 20th July 2013, 03:32 PM   #8
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My memory is a little fuzzy, but I remember the ultrasonics required a lot of spl to work properly and the HF had quite a lot of attenuation in air. Also, there was concern about the effect on pets and wildlife.
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Old 20th July 2013, 03:45 PM   #9
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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.

Last edited by Greebster; 20th July 2013 at 03:48 PM. Reason: addressing who?
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Old 20th July 2013, 03:53 PM   #10
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4Torr,
You are correct. This covers about every small animals hearing range.
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