The sound of applause, explained by physics

A round of applause, please: scientists have finally realized what stands after the sound of applause.

The research sets out a mechanism called a helmholtz resonator – the same acoustic concept that highlights the sound made when blowing at the top of an empty bottle. Experiments using children’s dust to design airflow, along with pressure measurements and high speed video, confirm that the explanation, researchers report on an accepted paper Physical review research.

A helmholtz resonator consists of a closed air cavity – like the inner part of a glass bottle, or space between the hands of the applause – with an opening attached to the cavity with a neck. The air shakes back and forth inside the neck, creating sound waves of a frequency that depends on the volume of the cavity and the dimensions of the neck and opening.

When a person shakes hands, an air plane flows from a trench where the hands meet, between the thumb and the thumb. “This air plane carries energy, and this is … the initial beginning of the sound,” says the mechanical engineer Yicong Fu of Cornell University. The plane begins the vibration of air. Fu and colleagues saw a similar effect using silicone patterns in the shape of cups designed to imitate the palms that hit together.

The researchers studied applause in various configurations: full hands, flat hands with palms clinging together and fingers hitting one palm. The sound frequencies that the registered team coincided with the predictions of the Helmholtz resonator theory. For example, catching hands when the applause produced a larger cavity-and a sound raised below-as applause with flat hands.

Understanding the physics of hand clapping, Fu says can help develop methods to identify people through their claps – for example, allowing users to enroll on a device based on their unique clip. Or can help musicians regular songs with the perfect hand beat.