Sound Wave Salt Plate Visualization

A portable Bluetooth speaker

A thin plate or plastic wrap stretched taut

Fine salt

A phone or device with a tone generator app

Optional: sugar, pepper, and sand for comparison

Place a speaker face-up and set a thin plate on top.

Sprinkle a thin, even layer of salt across the plate.

Play a single sustained tone (use a free tone generator app).

Watch the salt dance and settle into geometric patterns.

Change the frequency — try 200Hz, 400Hz, 800Hz — and watch patterns morph.

Lower frequencies create larger, simpler patterns. Higher frequencies create smaller, more complex ones.

Swap salt for sugar or pepper and compare how different materials respond.

These patterns are called Chladni figures, discovered in the 1700s. Your child is recreating a real physics experiment.

The salt collects along the nodal lines — places where the surface isn't vibrating.

Use a phone's slow-motion camera to capture the salt bouncing. The footage is mesmerizing.

Try playing actual music instead of tones — the patterns become chaotic and beautiful.

This makes sound visible. Kids who are visual learners suddenly understand sound waves in a way words can't convey.