A modular block-based acoustic metamaterial absorber with coiled cavities for enhanced sound absorption

A modular block-based acoustic metamaterial featuring perforated panels with straight and coiled cavities is presented for enhanced low-frequency and broadband sound absorption. The central panel is supported by the platform formed by the coiled cavities of four sub-units. The components are assembled modularly, allowing the absorption performance to be readily tuned by adjusting cavity parameters without altering the overall dimensions and perforation parameters. The impedance model is formulated using the perforated panel theory, together with the acoustic-electrical analogy, which is validated through acoustic experiments and finite element method (FEM) simulations. The complex frequency plane method is utilized to analyze the sound absorption coefficient (SAC). The coiled air cavities effectively elongate the acoustic propagation path. By adjusting the sub-unit configuration, the SAC of the studied absorber is higher than 0.8 within the frequency range of 664-1197 Hz. Furthermore, the absorption peak can be shifted downward to 242 Hz without changing the overall dimensions. A Genetic Algorithm (GA) is introduced to optimize the coiled cavity parameters of the metamaterial unit, enabling the optimized configuration to achieve a half-absorption bandwidth of 600 Hz. This work presents a design strategy to achieve a tunable metamaterial absorber with enhanced low-frequency and broadband absorption.