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.  

 

Step 2: Amplifying Cone

I bought my speaker from my local Maplin branch in the UK.

I took the speaker to my local DIY store to match it with the most suitable bucket with a matching diameter.

This one in particular is great : it is made of thin stiff metal that conducts vibrations very well. I am not sure if the membrane would vibrate more if I made a hole in the bottom of the bucket, I would imagine so.

1. So the idea is to roll some sugru in long rolls. 
2. Install the long sugru rolls on the most outer ring of the speaker. 
3. Make sure that the sugru is not interfering with any moving parts. 
4. Flip the bucket upside down, opening facing downwards. 
5. Install the speaker on top of the bucket bottom.
6. Adjust the level roughly with 2 mini-spirit levels if you have them
7. Prepare 4 or more contact points between the speaker and the platform. 
8. Assemble the platform on top of the amplifying cone and speaker. 

TOP TIP:
If you hesitate, I recommend to watch the video again, it makes it much easier to understand that text. 

Step 3: Install the Membrane

This is quite a delicate step.

You want a lot of tension on this membrane but you do not to perforate the membrane.

I would suggest the following steps :

1. Position the plastic sheet with A LOT of slack
2. Hold the sheet in position with a rubber ring
3. Create a "belt" of adhesive around the bucket, cut the slack
4. just like when you adjust a traditional percussion, you want to adjust the tension on one side, and immediately adjust on the opposite side. 
5. Eventually you can gently tap on the surface and find out if the tension is correctly distributed. The idea is that it would sound like a high pitch percussion drum. In fact, you could use an adjustable drum membrane to do this even more accurately, here an awesome video of how to adjust a darbuka head skin here (watch the end, spectacular!).   

Step 4: Assemble and Adjust

Before you use the rig:

1. it is level
2. your neighbours do not mind low and high pitch loud sound to be played.  
3. I recommend you use earplugs. Do not use noise cancelling headphones. 

Step 5: Software

There are many softwares out there to create and play plain waves from your computer. 

I personally use a mac, and I was running Tonegen demo, but I hear there are many options. 

- A very simple sine wave generator by the sine wave orchestra
- MAX MSP
- Spongefork
- there is so many I let you decide which you want to use :)
- http://en.wikipedia.org/wiki/Signal_generator

You could also use an analog wave generator, again there are many out there. Would be great if in the comment you could recommend me an affordable and powerful one to make larger scale experiment. I also wonder if these experiments would work at microscopic level... Another Instructable, later !

Step 6: Play! /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

The frequencies I have played : 

Salt, in Hertz (mouvements per second)

• 160
• 260
• 300
• 320
• 450
• 700
• 4900
• 15000

With MicroSphere in Hz (they look like they behave like a liquid at certain frequencies)

• 120
• 175
• 260
• 300

I tried also with flour, but it felt too "heavy", and sticky. 
Maybe because of the microscopic texture and elasticity of flour... I would love to do more experiments with even presumably even stickier materials such as potato starch... Next experiments!