Dr Michelle Dickinson: nanotechnologist explains where the science of clapping comes from - The Sunday Session with Francesca Rudkin

Most of us think clapping is just about two hands hitting each other, but new research out this week in the journal Physical Review Research found that the clap that we hear actually comes from the air being squeezed out between our palms.    

When your hands come together, whether flat or cupped, they trap a tiny bubble of air. That bubble escapes through small gaps, like the one between your thumb and index finger, creating a mini jet of air that blasts out and disturbs the surrounding atmosphere. 

This results in a burst of sound created by a phenomenon called Helmholtz resonance, the same thing that happens when you blow across the top of a bottle. Your hands, in that moment, are transformed into a musical instrument. 

To test their theory, the research team built silicone hands of different shapes and stiffness levels, and gave them microphones, pressure sensors, and high-speed cameras. They clapped the hands together again and again, studying every tiny movement and sound wave. 

They found that the shape of your hands plays a big role in how your clap sounds. Cupped hands trap more air and make a lower, deeper sound. Flat hands create a higher-pitched pop. Even the grooves between your fingers contribute, acting like tiny open-ended pipes that add extra tones. 

The study showed how a handclap might actually be used to identify someone. Because everyone has differently sized hands, skin textures, and clapping styles, no two claps are exactly alike, each person’s clap is unique, like a musical fingerprint. 

One researcher is already exploring whether clapping could be used to take attendance in classrooms - where students walk into a room, clap once and the system recognises you and checks you in. 

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