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Is there a way to make an ultrasound-to-sound "audio spotlight" DIY? Answered

http://en.wikipedia.org/wiki/Sound_from_ultrasound

The Holosonics Audio Spot Lightsells for $2,500, and the competing Sennhieser AudioBeam sells for $4,500.

Is it possible to do something like this home-made?

20 Replies

user
jr454 (author)2018-01-24

The cheapest Audio Spotlight is only $999, not $2500, and the Sennheiser one hasn't been on the market for a decade. FWIW.

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jr454 (author)2018-01-24

The cheapest Audio Spotlight is only $999, not $2500, and the Sennheiser one hasn't been on the market for a decade. FWIW.

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Asier Marzo (author)2016-08-29

Do not give up.

We will publish soon an Instructable about how to do it with an Arduino and components that you can buy on Amazon for less than 70$ (the most expensive things are the transducers).

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user

Hi, I have published some acoustic levitators www.acousticlevitator.com and one of them contains a quick and dirty directional speaker. However, I am still working in the good directional speaker Instructables, I want it as cheap as possible and with better sound quality than the commercial ones.

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whitsona (author)2015-11-26

I'm interested in trying this one at home as well. Have you made any progress since you posted this 5 years ago? I see that there were some papers in Japan in 2012. And there are some ultrasonic haptic devices out now-- at least MIT has one that is pretty high res now according to their video.

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endolith (author)whitsona2015-12-01

I haven't tried anything with it, no.

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whitsona (author)2015-11-26

Oops-- guess you posted it even earlier than 5 years ago. Guess you were just still commenting on it 5 years ago.

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dragonbtv (author)2012-03-04

I'd like to make a test from smaller transducers units.

But, before that, any comments about the harmfulness of heavy ultrasound wave, any US standard?
It looks like the "audiosportlight from Holosonics" did neither mention the harm nor warning of their products.

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7heaven (author)2011-03-08

someone already did it!
http://zao.jp/radio/parametric/index_e.php

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moose224466 (author)2010-11-30

It works by using tartini tones, or also called combination tones........so if you have a transducer producing 200,000 hz along with 200,700 hz there is a third tone that can be herd which is 700 hz..... aka the difference........

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DELETED_GuardianFox (author)2009-04-20

Yes, it's possible. The parts are readily available... BUT... I haven't found out yet exactly HOW they accomplish what they do. Yes it's a transducer spitting out sound in the ultrasonic-frequency range... but how does the controller know how to modulate that ultrasonic frequency so that it vibrates the air in JUST the right way to create audible sound?

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user

It's high intensity, so that the air becomes non-linear and demodulates the sound directly. The Wikipedia article says it uses heterodyning for modulation and a parametric array for aiming the ultrasound beam

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user

No offense, but that's not explaining how they modulate the "beam." What formulae are used to translate from one form to the other, accuratly?

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user

Note that this is vaguely similar to the laser plasma volumetric display. The energy is likewise focused onto a point in the middle of the air, and when energy is concentrated in a small enough volume, the air does strange things, in this case becoming a plasma that glows.

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user

Hmmm... guess I should just read some papers. :)

"An ultrasonic speaker creates audible sound in air by means of the nonlinear interaction between ultrasonic waves. The speaker emits two ultrasonic waves of different frequencies into the air. If the two waves have high enough intensity, nonlinear interaction of the two waves occurs in the air, which results in a low frequency audible sound."

"A finite amplitude ultrasound wave that can be amplitude modulated by any audio signal is radiated from a transducer array into air as the primary wave. As a result, an audio signal is produced in the air because of the self-demodulation effect of the AM sound wave due to the nonlinearity of the air. It is possible to get a flat characteristic of reproduced sound pressure by using an equalizer."

"Until now, most ultrasonic speakers have utilized piezoelectric buzzer-like radial mode transducers, which necessitates a complicated signal processing circuit to overcome the narrow frequency bandwidth of the transducers. We designed an ultrasonic speaker with thickness mode piezoceramic transducers, and fabricated an ultrasonic speaker system working at a frequency of 650 kHz. The design method of an individual in-air piezoceramic transducer is presented, followed by the design of the parallel combination of many transducers that are used to make the speaker. The performance of the speaker was measured experimentally to verify its unique features; i.e. a high directivity and a wide frequency bandwidth. The ultrasonic speaker developed in this study preserved all the unique features of an ultrasonic speaker without the use of complicated electronic signal processing circuits by virtue of the broadband frequency characteristics of thickness mode piezoelectric transducers."

The other possibility for directional sound is just a phased array of normal speakers...

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roy44 (author)2010-08-17


The smaller one is $1999 retail, which is a bit cheaper, but they might have cheaper units if you ask. But from what I know the ultrasound transducers are not cheap! ($2-$3 each, and you need a LOT of them). (The Sennheiser link is broken.)

There isn't much specific information about modulation on the Audio Spotlight website, but there is a page describing why a phased array can't make directional sound:

http://holosonics.com/tech_directivity.html

I don't know what all this "teeth and bone" stuff is, though.

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endolith (author)roy442010-08-25

"A phased array can't make directional sound" refers to playing audible sound directly through speakers. Higher ultrasound frequencies can be focused with a phased array, which is why they use them as the "carrier".

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HSOONG (author)2010-08-06

Forget about all the myth said in the web these days! How can you contain the sound within a small area and why need an array of transducer to contain it. The orginal web info had been altered long ago. Forget about all the ultrasound convert into sound stuff, if it is even true. The secrete is " your teeth and maybe the bone near it" which will act as transducer in converting ultrasound to bone transmitting sound directly to you ears no AC5.1, mono only sorry.

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endolith (author)HSOONG2010-08-25

I don't think you're talking about the same thing I am.

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