How to make a Chladni plate (vibrating membrane)

One can "see sound". Or... "A plate or membrane vibrating at resonance is divided into regions vibrating in opposite directions, bounded by lines of zero vibration called nodal lines." [wikipedia]

These are figures are made with salt on this rig. 

I have seen many ways I could build my own DIY vibrating Chladni plates (Cymatics) but I was generally frustrated by the fact that one would generally have to sacrifice a speaker in the process, and I would need to have a super powerful sound amplifier. I wanted to

• work with cheap off the shelf components
• use as much of my own kit as possible (my conventional audio amplifier etc.)
• avoid destroying the speaker
• use a plastic membrane that is cheaper and requires less power (less noise for my neighbours)

This is how I built this rig. 

Sugru is ideal for this project because:

• It provides a great acoustic contact that bonds to plastic sheet, board, metal, glass
• creates a perfect seal between the speaker and the plate
• you have time to make the whole set-up level before the sugru cures
• can also create custom-made dampening pads for the contact with the table the rig sits on.

Bonus:

• I don't need to destroy my nice speaker since I can cut sugru and re-use my speaker once the experiment is done

If you need to stock up on sugru, you can buy it here and also from the Instructables store.

I recommend this instructable especially for educators as it makes a great intuitive and hands-on introduction to acoustic with exciting experiments but without spending too much. 

Going with this instructables, you can find classes that will teach you general concepts of standing waves, cancellation and many other phenomena. 
- the physics Classroom
- UCLA acoustic

This instructable has been made by Cesar Harada at TechShop SF for Sugru

So lets get started!

Step 1: Build the base

http://youtu.be/3WHRIMecov8

So, here we go! These are the things we will need to build this. 

Part List

• Computer _ £ 0 (we assume you already have one)
• Sound amp _ £ 0 (we assume you already have one)
• Speaker (here I use a 10W car speaker) _ £10 at Maplins (UK) / Radioshack (USA) If you want to use a more expensive speaker you already own, you can! Especially because it is easy to cut and remove sugru. 
• Paint bucket _ £2.5 at the local DIY paint shop
• Plastic membrane _ £3 
• Set of 4 x M5 (5mm) nuts and bolts _ £ 2.5
• Duct tape _ £2
• Rubber ring _ 0.10
• sugru 3x5 gr _£ 6.5
• Scrap wood board
• _TOTAL BUDGET  = £26.6 ( $ 41.25)

Tools

• Cordless drill + drill bit ø5mm
• Ruler / 90 angle
• Pen
• Spirit level

Time

• 1.5 hours to build with 2 people
• 6 hours for sugru to cure (overnight)
• 3 hours to play with tones

To start with we are going to build the adjustable platform that will support the speakers.
I had some scrap wood laying around. I simply drilled holes in the corners and passed my M5 nuts and bolts through.  

 

Comments

[bigattichouse]

Hi, I wonder if you could use this to separate materials by density? If you mix two different sizes of sand (one colored, one white)... would you get a core mass of the lighter material, surrounded by the heavier?

[cesar harada]

That is correct. From my experience from running the same frequency for a long time, I had grains of salt breaking to finer grain of salt and eventually the smallest grain would concentrate in the center when the bigger grains would progressively fall off the from the membrane. After 5 minutes at the same frequency I only had very fine salt dust left, all the big grain had fallen out.

[bigattichouse]

Just hope no one applies the principle to uranium enrichment ;)

[cesar harada]

HAHAHAHAHA! Is that how you do it? mmmmm .... Interesting (with evil eyes and skinny fingers).

[Kiteman]

Oh, this is an excellent demonstration, although I doubt any professional teachers that make one will actually dismantle it, since they'll need to use it several times every year.

[cesar harada]

Good point. But what if the teacher wants to upgrade his setup? He can do that by simply cutting the sugru and attaching a new amplifying cone / membrane. Because the "glue" (sugru) is easy to remove it is an evolutive platform.

[Kiteman]

Good point, well made.

("Evolutive platform" - I am *so* going to steal that phrase!)