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We clap to get people’s attention, to say “congratulations” and even to make music. But have you noticed that everyone’s claps sound a little different? A team of physicists have now figured out why, and they think we might one day be able to tell who someone is just from their claps.

“This started as wanting to understand something I saw and something we do every day. When I see something, I try to question why it happens,” says Sunny Jung from Cornell University in the US.

There are lots of different ways that people clap their hands. In this experiment, Sunny’s team asked people to use just three styles. These included: clapping with flat hands, clapping with cupped hands (forming a kind of C-shape) and clapping with fingers to palm. The physicists put baby powder on the hands to see how the different clapping styles caused air to move differently. And they used high-speed cameras and microphones to catch it all happening.

“We wanted to explore how we generate the sound depending on how we clap our hands,” says Sunny.

They found that the sound of a clap comes from a jet of air that gets forced out from between the palms. And clapping with flat hands makes a higher pitched sound than clapping with cupped hands, because there is a smaller space between the palms. Try it! Can you hear the difference?

Sunny’s team also figured out that the softer the hand shape was, the quicker the clapping sound went away. This is because the soft, fleshy parts of the hands vibrate after each clap, which absorbs some of the sound energy. So, Sunny says that if you want to get the attention of another person very far away from you, you might want to choose a clapping shape that makes your hand harder, like flat hands.

Since we all have different hand sizes, clapping techniques, skin textures and hand softness, we all make different sounds when we clap. So, one of Sunny’s students is testing whether the sound of a clap could be used to do the roll call in class!