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Directional speakers

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moffy:
Saw this video where an array of ultrasonic transducers are modulated with an audio signal and it ends up as a directional audio speaker. I expect the distortion would be terrible, but it is an interesting concept.

Marco:
Are you sure this is a directional audio speaker and not a directional ultrasonic speaker? Usually it's the high frequency modulated signal being down-mixed which creates audio.

Wonder if the commercial versions use higher frequency transducers, so they don't have to swing so much from their resonant frequency. You can probably find some data in patents, or maybe the audio engineering society journal.

moffy:

--- Quote from: moffy on January 13, 2025, 01:16:20 am ---Saw this video where an array of ultrasonic transducers are modulated with an audio signal and it ends up as a directional audio speaker. I expect the distortion would be terrible, but it is an interesting concept.


--- End quote ---

--- Quote from: Marco on January 13, 2025, 01:31:09 am ---Are you sure this is a directional audio speaker and not a directional ultrasonic speaker? Usually it's the high frequency modulated signal being down-mixed which creates audio.

--- End quote ---
Not sure of the distinction you are trying to make, as mentioned the ultrasonic signal, the 40kHz carrier is modulated with the audio signal, and appears to the listener as directional audio.

ledtester:
You might also want to check out the SonicSurface:

https://hackaday.com/2021/08/18/phased-array-levitation-is-science-in-action/

https://youtu.be/vAEZvYlUnEM

which is a 256 element ultrasonic array using an FPGA to individually control each transducer.

(There is also an earlier version of the project utilizing 64 transducers under the control of an Arduino Mega:

https://youtu.be/h0Mh0bIv9Fk

)

A main feature of this project is the PC software, Ultraino, which helps you create custom acoustic fields - for example levitation choreographies involving multiple points.

You can see the software in action here:

https://youtu.be/vAEZvYlUnEM?t=8m47s

It also can be used as a directional speaker with directionality controlled via software:

https://youtu.be/h0Mh0bIv9Fk&t=10m53s

moffy:
I certainly will have a look at the links. :)

P.S.
has a nice simple explanation of the physical principles involved, as well as a simple test circuit.

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