Science & Pitch with Sprinkles On Top

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Have you seen this?

 

 

I saw this video about a year ago and became obsessed with making a Chladni plate. The problem is Chladni plates are actually pretty complicated to make and I’m not all that mechanically inclined.  But I kept thinking, “There has to be a easier way to make one.”

And guess what …

I found a way.

Here’s what I used …

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I bought the putty, steel sheet, and speaker on Amazon.  Here is exactly what I ordered…

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The steel sheet is 12 gauge, which is important because you need it to be solid yet thin enough to vibrate. The speaker needs to be a vibrating speaker with a flat surface for mounting the metal plate. There were more expensive speakers but I decided to start cheap and it did the job.

The assembly – if you can call it that – is very simple. Put a dab of putty in EXACTLY the center of the metal plate, then position the center of the speaker on the putty. Getting it centered is the most important (and the hardest part) of this.  If the plate isn’t centered everything will run off to one side.  You’ll be able to tell if it’s centered in the next step.

Now you need to generate pure tones. I used this This website, although there are others and even apps. You could also use a tuner that plays pitches.

Pure Tone Generator

Connect your speaker to the pure tone generator using an aux cord or blue tooth.  Turn it on and put some sprinkles on the metal plate. Most examples I’ve watched of chladni plates use salt or sugar but I found the white material difficult to see. Colored sugar sprinkles were much easier to see, but I recommend using the sugar crystal sprinkles, NOT the tiny round ones as they will roll right off. I put trash bags under the speaker and pieces of construction paper so I could easily catch what fall off the plate and reuse it.

Now, just start experimenting and have fun! You’ll need to adjust the tones up and down to find frequencies that produce a good vibration – not all of them do. As you do this, you’ll see if your plate is balanced. If it’s not the sprinkles will all drift to one side as they vibrate.  If it IS balanced, you’ll get the amazing designs. Just keep adjusting until you get it right.

Here’s a clip of what ours was able to do once it was pretty well balanced.

Aside from this just being cool to watch (which you might want to do to start with), you can use this for science and music concepts. Pitch and frequency is an obvious concept to associate with the tones.  I found it interesting that when the designs are formed the sprinkles go to the places that DON’T vibrate. Also, as the frequency (and the number of vibrations) goes up, the designs become more intricate.

My students often confuse volume and pitch. This experiment gives a good demonstration between the two and how they are related but not the same.  When the pitch is very low and the vibrations are very slow, the tone sounds quiet – perhaps because such a small strain is being placed on your ear drums. You notice, however, that the pitch and frequency will get so high that it makes your ears hurt – not because it’s so loud but because it’s making your eardrum vibrate so fast.

Finally, I don’t want to discount the pure artistic value of the designs that are created. Recreating them or taking photographs could be an amazing art project.

I’m sure your collective knowledge and creativity can come up with even more concepts to be discussed as you do this experiment. Please share what you try with your students!

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