everybody clap your hands Study: Hand clapping is akin to a Helmholtz resonator Faster clapping yields lower-frequency sounds, as does cupping one's hands while clapping. Jennifer Ouellette Mar 12, 2025 2:06 pm | 3 Credit: Yicong Fu et al., 2025 Credit: Yicong Fu et al., 2025 Story textSizeSmallStandardLargeWidth *StandardWideLinksStandardOrange* Subscribers only Learn moreHand clapping is ubiquitous behavior for humans across time and cultures, serving many different purposes: to signify approval with applause, for instance, or to keep time to music. Acousticians often use a hand clap as a cheap substitute for pricey equipment to make acoustic measurements in architecture. While the basic physical mechanism is simple, the underlying physical mechanisms are less well-understood.A new paper published in the journal Physical Review Research provides experimental support for the hypothesis that hand clapping essentially acts like a Helmholtz resonatorakin to the hum generated by blowing across the top of a bottle, or the hiss one hears when holding a conch shell to one's ear.In 2020, engineers Nikolaos Papadakis and Georgios Stavroulakis, both at the Technical University of Crete, recruited 24 students to clap their hands once in different venues, varying their hand configurations in 11 different wayschanging the angle of the hands with respect to one another, for instance, or changing how many fingers of one hand overlapped with the fingers or palms of the other.The results: The hand configuration that produced the loudest clap85.2 dBconsisted of holding the hands 45 degrees to each other with the palms partially overlapping. If one were more interested in producing a richer range of frequencies, it's better to ensure one's palms are completely overlapping and shaped into a dome, enclosing a pocket of air. (The same 45-degree hand orientation applies.) The second configuration didn't produce as much of a shock wave as the first. Papadakis and Stavroulakis concluded that holding one's hands flat or in a dome while clapping produces the equivalent of a Helmholtz resonator.There has been a great deal of research into Helmholtz resonance in general, but according to Yicong Fu of Cornell University and co-authors, there has not been any significant attempt to cross-confirm that human hand claps serve as Helmholtz resonators. So they recruited 10 participants to clap into a microphone 2030 times each for three different hand configurations: cupped, palm to palm, and palm to finger. They used baby powder to map the air flow produced by the clapping, along with measuring pressure and capturing the action on high-speed video. They also made soft polymer hand replicas designed to mimic the elasticity of human skin and used them to generate clapping sounds for comparison. Yicong Fu et al., 2025 Yicong Fu et al., 2025 Yicong Fu et al., 2025 Yicong Fu et al., 2025 Yicong Fu et al., 2025 Yicong Fu et al., 2025 The recorded frequencies matched the predictions of the Helmholtz resonator model, confirming that hand claps function like a resonator, rather than being a solid collision sound. Frequency depended upon hand configuration: clapping with cupped hands, for instance, produced lower frequencies than clapping with palm to finger because the cupped configuration created a larger resonant cavity. Clapping faster produces a louder initial sound, while lower skin elasticity produces a longer-lasting sound.In short, "Our work provided the first experimental support for the theoretical framework and improved the fundamental understanding of hand claps for broader application potentials," the authors concluded. Specifically, "These findings may facilitate low-cost acoustical diagnostics in architecture and enhance rhythmic sound patterns in music and language education." It might even be possible one day to identify someone based on their distinctive claps and use it as a kind of acoustic login for electronic devices.Physical Review Research, 2025. DOI: 10.1103/PhysRevResearch.00.003000 (About DOIs).Jennifer OuelletteSenior WriterJennifer OuelletteSenior Writer Jennifer is a senior writer at Ars Technica with a particular focus on where science meets culture, covering everything from physics and related interdisciplinary topics to her favorite films and TV series. Jennifer lives in Baltimore with her spouse, physicist Sean M. Carroll, and their two cats, Ariel and Caliban. 3 Comments