The tymbal of a cicada: nature's sound-generating metastructure.

Cicadas generate sound through the interplay of tymbal buckling and body resonance, but a unified framework explaining the diversity of calls across species has been absent. In this study, we conceptualize the cicada's sound-generation mechanism as a naturally occurring biological metastructure, characterized by periodically arranged ribs and inherent frequency filtering. We introduce a novel mechanical model comprising a chain of bistable oscillators coupled to a chain of resonators, which successfully captures both the snap-through dynamics of the tymbals and the subsequent acoustic filtering. This model represents the first species-adaptable framework capable of reproducing the distinct song frequencies and call patterns observed across multiple cicada species, offering a new understanding of this remarkable biomechanical system.