Seeing Sound - Chladni Plate From Household Objects

Chladni plates are a classic physics experiment that reveal the hidden patterns created by vibrating surfaces. Using only a metal cake-tin base, a Bluetooth speaker and some table salt, you can create beautiful geometric designs that shift and change with sound frequency.

This build is quick, inexpensive, and perfect for classrooms, workshops, or demonstrations.

You will need:

1. A bluetooth speaker
2. A metal plate (like the bottom of a cake tin)
3. Salt

Optional (for experimentation):

1. Sugar
2. flour

Balance the metal plate on top of the bluetooth speaker.

Sprinkle a light, even layer of fine table salt over the metal plate, use a sieve to help spread it out if you like.

Don’t pile it up, use just enough to coat the surface. Too much salt will damp the vibrations but too little may make the patterns hard to see.

Connect your phone/laptop to the bluetooth speaker and open up a frequency generator.

I used this one: https://www.szynalski.com/tone-generator/

Make sure the speaker volume is moderate to high and play a sine wave tone. Slowly sweep through different frequencies and watch how the salt behaves.

You’ll notice at most frequencies the salt sits still, but at certain frequencies, the plate resonates and the salt starts moving.

When that happens, the salt jumps into distinct lines and shapes which correspond to a vibrational mode of the plate.

Try:

1. Higher vs lower frequencies
2. Adjusting plate position
3. Different volumes
4. Different amounts of salt
5. Using sugar or flour

You’ll discover multiple resonances, each creating its own geometric arrangement of lines, islands, and nodes.

Every plate shape and material has its own signature of possible patterns.

When sound waves from the speaker vibrate the metal plate, the plate oscillates in complex ways.

At most frequencies, the vibration is weak and the salt stays still on the plate.

But at specific frequencies (called resonance frequencies) the plate vibrates in stable patterns known as standing wave modes.

These modes divide the plate into:

1. Antinodes - regions that vibrate strongly
2. Nodes - regions that barely move

Salt naturally collects on the nodes, because vibration shakes it away from antinodes. This forms the intricate patterns you see.

The shapes depend on the plate’s geometry, its thickness, how it sits on the plate and the frequency of the vibration.

This is the same physics behind musical instrument acoustics, vibration analysis in engineering and even structural testing in aerospace.