Abstract Helmholtz resonators have long been essential for acoustic control,
enhancing or nullifying sound at specific frequencies. Traditionally, these resonators are
effective for fixed-frequency applications, but lose efficacy if the excitation frequency
changes. This paper presents the first tunable broadband origami-based Helmholtz
resonator, featuring a compliant origami design with auxetic properties for optimal
volume variation. Multiphysics simulations determined the adaptive cavity geometry,
and experimental tests validated the models, showing high tunability (up to 25%
around a central frequency of 461 Hz with a 95% absorption rate) and broad bandwidth
(up to 13% around the central frequency with a 95% absorption rate) with minimal
geometry variation (8 mm in diameter). This work marks a significant advancement
over traditional Helmholtz resonators.