Sound of a handclap: An elastic Helmholtz resonator

Handclap is one of the most common human body languages for expressing approval and attracting attention. Despite the simple motion, numerous factors influence the acoustic output. Previous work on human subjects had suggested the relevance of hand configurations (Repp 1987). Nevertheless, the systematic study of the acoustic performance of a handclap has not been comprehensive. In preliminary studies, we observed an order of magnitude change in frequency with different cavity volumes and an amplitude change as a function of clapping speed. To further the understanding, we modified the traditional Helmholtz resonator model suggested by Fletcher (2013) to better capture the influence of cavity size, air outlet size, neck length, and clapping speed, experimentally. In addition, we considered the elastic modulus and deformation of the material for their effects on the frequency to discuss the validity and limitations of the proposed model. Reality-comparable reduced-order silicone hands for parametric studies were manufactured based on the dimensions from 3D scans of actual human hands. The frequency, amplitude, material dynamics, and fluid motion upon clapping were quantified from audio and high-speed images. Data from human subjects were also used to further verify the applicability of our experiment setup and validate our proposed theoretical model.