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Author Topic: How to construct a waterproof sound box to emit vibrations/Chladni plate?  (Read 1005 times)

Offline Garvock

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I am an art student currently at the beginning on an Art, Science and Visual Thinking module. My initial research has led me to Chladni plates where sand can be used to visualise sound vibrations, and the use of a non newtonian fluid on a  speaker using certain frequencies. My current aim is to create my own Chladni plate where I use a loudspeaker and something that emits a tone at certain frequencies as research, I also hope to experiment with a high speed camera and perhaps oil and water to capture the patters and relations made by the sound vibrations. Once this is done I hope to create artwork which is based on these patterns.
The issue that I have is I am primarily an artist, I most often spend my time researching art and creating things for my degree course. I am not technologically minded, or scientifically minded for that matter and so the maths, science and technology of what I am wanting to do goes completely over my head. So I need to create an enclosure of some sort which is fair enough, I can do that, but when it comes to the speaker and how to emit the tone/vibrations I am a bit lost. Some research on speakers has uncovered that I can purchase low range, mid range and high range speakers, I don't really know what the difference is.
Is there anyone with knowledge of speakers/electrics that can advise me of a cost effective way of re-creating the Chladni plate and what speaker type/size is the best to purchase?
Also I would assume that water on most speakers would cause damage? and so I therefore assume that I would also need a waterproof speaker?
Any advice would be greatly appreciated,

Thank You


 

Offline Colin2B

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For a small plate of about 1-2ft each side almost any midrange speaker will do.
A good one to use is from a car sound system as they are often quite high power and they are compact enough to mount in a piece of plastic drainage pipe. Be careful to use ear defenders as you will need to turn the volume up. Input to the amplifier can be from an iPod or iPad and there are tone generator apps on the net.

Water and oil can get messy, I use tea, some use glitter.
If you have to use liquid I suggest you keep the speaker tube close to the plate and the plate wider than the speaker diameter.
You can suspend the plate on elastic bands or pieces of foam, just place them where you expect the nodes to be ie where the liquid/glitter accumulates.

Good luck.
Post some pics when you have results.
 

Offline Garvock

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Thanks for your reply,

With regards to the speaker is there a best wattage/size? Also this may seem a silly question but do I also need to purchase an amplifier?
 

 

Offline timey

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Why don't you just recreate the Chladni experiment techniques?  Running a violin bow up and down on the side of a plate covered with flour, or a sheet of metal covered with sand...

***edit: I had written some suggestion of a speaker, but have deleted it as Colin's suggestion is better, and he has mentioned the tones available on net already... but yes you will need an amplifier to drive the speaker***

A flat bottomed and mirrored bowl for the water would make for the most interesting results...  Try darkening the room and shining a laser through the water, or spotlighting the water and dripping drops of coloured oil paints in...

Also, a trampoline in the rain makes for an inspirational observation of frequency and vibration effects.  Could be a route to some ideas.

Good luck with your project.  I'd also be interested to see some of your resulting pictures if you fancied posting them...
 

Offline Colin2B

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Thanks for your reply,

With regards to the speaker is there a best wattage/size? Also this may seem a silly question but do I also need to purchase an amplifier?
20W should be adequate, but as you arent trying to drive higher order patterns you could get away with 10W.
Yes you will need an amp and it neednt be anything special, an old sound system will do eg one with a broken CD player, you just need an aux input for the signal generator.

I like Timey's suggestion of using the water bowl, you might need to put the speaker frame in contact with the bowl. These wont be the same patterns as on the plates, but they will be interesting.

If you use a plate you can modify the standard patterns which are formed on plates of uniform stiffness and density. Stiffness is hard to change, but you can change local density by adding mass eg use poster putty to add weights such as steel nuts to the bottom of the plate, this will pull the patterrn out in that area.
« Last Edit: 02/10/2016 17:34:13 by Colin2B »
 

Offline RD

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I am an art student currently at the beginning on an Art, Science and Visual Thinking module. My initial research has led me to Chladni plates where sand can be used to visualise sound vibrations ...

Rather than working with messy powders, you could glue a piece of mirror to a loudspeaker, then bounce a laser-beam (laser-pointer) off the mirror ...
https://youtu.be/QGeFF5Q_c5g?t=40s
https://www.youtube.com/watch?v=RxzMzSZF_b4

https://wikipedia.org/wiki/Lissajous_curve

My current aim is to create my own Chladni plate where I use a loudspeaker and something that emits a tone at certain frequencies as research ...

If you must have Chladni patterns, a soap-film can be vibrated with a domestic* audio equipment ...
https://www.youtube.com/watch?v=0pnxk3fl_Fo

 
https://www.youtube.com/watch?v=AuAjEEMW3XM

[ * vibrating a sheet of metal, or cup of coffee, to produce Chladni patterns would require expensive high-power audio amplifier , which would be deafeningly loud ]

...I also hope to experiment with a high speed camera and perhaps oil and water to capture the patters and relations made by the sound vibrations

Chladni patterns are created by standing waves , so you won't need a special high-speed camera to capture them. 
« Last Edit: 02/10/2016 17:45:41 by RD »
 

Offline Garvock

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Brilliant, thank you!

Some great ideas there that I will keep in mind. I will definitely post some pics once I have achieved something.

If an old CD player would work to amplify the sound would the same principle occur in a tv sound system? My tv has a blu-ray player connected which all the speakers are connected to for the surround sound. If I find an appropriate speaker will connecting that to my blu-ray player amplify the sound enough? I am not at home just now so can't confirm if it has an aux input, so I may have to use my tv as the input for the sound or my laptop connected through the HDMI.

If this is not an option I think I will just search the internet for a cheap(wish) speaker and amplifier.

Thanks again
 

Offline timey

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Ah Colin - there is nothing I like better than a respectable thought tangent, and the basis for node patterns, ie: energy density and frequency relates very closely to my investigation in other areas...

You say that a bowl of water may need to touch the frame of the speaker and that the node patterns would not emerge.  Clearly the receptacle making contact with the vibrating frame will change the pattern, but is this also because of the water?  For instance, if a Tibetan singing bowl was to contain some water and one dripped a drop of oil paint into the water and then drew a violin bow over the rim of the bowl - would the oil paint create a node pattern on top of the water?

BTW Govark, if you super glue a small mirror to the speaker cone centre and shine a laser onto the mirror, when playing tones of varying frequency the laser will create various patterns.

Edit: I see RD got there before me...

But Colin, RD - are these patterns created by a laser focused on a mirror being vibrated at these varying frequencies actually the node patterns that are occurring on a plate?
 

Offline Colin2B

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You say that a bowl of water may need to touch the frame of the speaker and that the node patterns would not emerge. 
I meant from the point of view of power transfer, you get more vibration with direct contct.
I hve an old loudspeaker with cone removed and a rod connected to the voice coil, this can be uss to drive an instrument bridge directly to get the patterens

But Colin, RD - are these patterns created by a laser focused on a mirror being vibrated at these varying frequencies actually the node patterns that are occurring on a plate?
What RD describes with mirror glued to loudspeaker will not be a Chladni pattern, but worth investigating for artwork.


If an old CD player would work to amplify the sound would the same principle occur in a tv sound system? My tv has a blu-ray player connected which all the speakers are connected to for the surround sound. If I find an appropriate speaker will connecting that to my blu-ray player amplify the sound enough? I am not at home just now so can't confirm if it has an aux input, so I may have to use my tv as the input for the sound or my laptop connected through the HDMI.

Although that should work sine waves have greater average power than music so it is easy to overload your system, best to use old equipment which wont matter if it blows a gasket. I use an old 20W CD player to drive musical instrument soundbourds.
Make sure your app can generate continuously variable frequency as you will need to sweep to find the resonances
 

Offline Garvock

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Again, thank you all for your replies.

I have ordered a speaker, the amplifier I might be able to source from somebody.

I will let you all know how I get on.
 

Offline timey

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It interested me whether or not a node pattern would occur in the Tibetan singing bowl containing some water and a drop of coloured oil because shining a laser through water that was moving in this way would be interesting.  I know that the pitch of the singing bowl will be of a higher frequency with water added.  But what does the water do, and would a node pattern form in an oil sitting on top of the water in the instance of the Tibetan singing bowl?  ie: does fluid change the node pattern? (I realise that this is probably some elementary type physics that I don't know cos I wasn't formally educated and its outside my experience)

Here is a video for Govark (payment for my tangents)

https://m.youtube.com/watch?v=yGGTmF6xjKI

Pretty funky stuff!

Colin - In the instance of the mirror stuck to speaker cone, the laser beam and the patterns caused at varying frequencies - if these are not node patterns, what are they?  Surely they must be closely related?  A node pattern is formed where the stresses of resonance are least in the structure of the plate and these node patterns relate to the Schrödinger equation.  If the mirror was being resonated by the frequency, a node pattern would form in powder placed on it, but the mirror is vibrating with the speaker.  By all logic this should result in Doppler shift?
« Last Edit: 02/10/2016 21:06:19 by timey »
 

Offline Garvock

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Excuse my naivety, but is the person in this video just shining light onto the water?

It almost looks like a 3 dimensional form, but I assume that this is just the light being broken up by the movement of the water?
 

Offline Colin2B

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Colin - In the instance of the mirror stuck to speaker cone, the laser beam and the patterns caused at varying frequencies - if these are not node patterns, what are they?  Surely they must be closely related?  A node pattern is formed where the stresses of resonance are least in the structure of the plate and these node patterns relate to the Schrödinger equation.  If the mirror was being resonated by the frequency, a node pattern would form in powder placed on it, but the mirror is vibrating with the speaker.  By all logic this should result in Doppler shift?
They are loci of the movement of the cone. Because of persistence of vision the light will trace out a continuous line similar to when you make circles with a sparkler. Sometimes they trace out patterns like the lissajous figures that you can display on an oscilloscope, depends on frequency and cone movement.
Node patterns are the stationary areas, ie minimum displacement, on a resonating surface due to standing waves, the indicator eg sand collects in these areas. The antinodes are areas of maximum displacement.
The relationship to shrodinger is that you can use similar maths eg wave functions, Fourier analysis,  and eigenvectors etc to analyse the response of the plate, but it's easier and more fun to use the sand.
Yes you will get Doppler shift, but it is too small for the eye to detect.

I'd be interested to see what result from the singing bowl. I know someone who has experimented with wooden bowls with strings stretched across - intriguing sounds. I haven't made one yet.
 

Offline RD

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Here's some still-images from the [MIT] soap-film video above ...

http://tsgphysics.mit.edu/front/demo.php?letnum=C%2040

It would be possible to get sharper images of the normal mode patterns,
 but the blur* & chromatic aberration have made it more artistic.

A coin-sized soap-film disc , (or square/triangle/etc) , could be photographed with a camera which has a macro lens. ~1 Watt of audio-power would be enough to vibrate a flimsy soap-film,
( wheras a VERY poweful audio-amplifier would be required to vibrate a bowl or cup of liquid ).

For the macro set-up a beam-splitter set at 45o , would be required to provide axial-illumination.
A transparent CD case would suffice as a beam-splitter, or cling-film stretched taught on a frame for a sharper image.

* If you want the blur, like the MIT soap-film images, de-focus the macro lens.
« Last Edit: 03/10/2016 06:31:28 by RD »
 

Offline vhfpmr

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I once left a glass coffee mug full of water on the draining board, with the inside of the mug covered with tiny bubbles clinging to the glass. When I went back later, the vibration from the washing machine under the draining board had dislodged the bubbles which had then drawn a Chladni pattern around the standing waves on the water.

I saw a similar pattern of bubbles in a bowl of tomato soup after I heated it in the microwave.
 

Offline timey

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Colin - Yes that's right.  The  node pattern association with Schrödinger is due to standing wave function in that a wavelength can only fit x amount of times within a confine.  The structure of the plate has its own natural resonance frequency.  To achieve a node pattern on the plate this resonance must be achieved.  Differently structured plates will resonate at different frequencies.

Going back to the laser beam trained on the speaker vibrated mirror - this is almost synonymous to the gamma ray emitter of the Pound Rebka.  Yes, of course the Doppler shift created is miniscule, but its enough to turn the dot of a laser beam into a pattern.  The frequency that the mirror and the laser beam is being vibrated at also causes a change in the pattern... What are the parameters of the changes?  Has anyone got any data?  What interests me is the notion that if the hertz were increased at a constant rate would the pattern displayed by the laser beam change linearly, or would there be jumps from one pattern to the next?

Surely there are node patterns that occur for every frequency?  ie: is it possible to create plate structures of different density that are engineered to resonate at each and every frequency?  I'd be interested to know how the patterns vary between frequencies, and again, if they change linearly or make jumps from one pattern to the next.

What would really, really interest me is a mathematical comparison between the node patterns at each frequency with the Doppler patterns at each frequency and establishing the relationship between the two... (my reasoning being that if the node patterns are being created in the points of least vibration on the plate, the laser beam patterns are being created from the points of most vibration of the mirror and therefore may possibly be the same patterns inversed.)

Do you know if there is any data like this?

*

Garvork - The scenario in the video is backlit from a ring submerged in the water. The water is being subject to the frequency of  440Hz and 432Hz.  Colin described how he has taken the cone off his speaker and can drive the sound straight from the voice coil to the sound board.  In this case the frequency is being driven into the water by the arm you see pointing into the ring of light visible just as the frequency is first applied.  What you then see is the motion and patterns subsequently induced by the frequency in the water molecules backlit by the ring of light.   Pretty mundane for the individual application of each frequency, can you see much difference? ...but when the two frequencies were combined, that was pretty wild wasn't it?

Here is some stuff on cymascope research and history.

http://www.cymascope.com/cyma_research/history.html
 

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