Broadband low-frequency sound absorption via a cross-bridged hex acoustic metamaterial with extended necks

Abstract

To simultaneously address low to mid frequency noise absorption and stringent thickness constraints, a novel cross-bridged hex structure with embedded necks was developed from conventional honeycombs. The acoustic performance of these metamaterials was systematically investigated via theoretical analysis, experimental verification, and numerical simulation. Results demonstrate that an exponential 2 penalty factor objective achieves superior uniformity of sound absorption within 500–1000 Hz band, surpassing both average-driven and multi-level reward methods. Among the four tested optimization algorithms, a hybrid CMAES + LBFGS scheme reduced the final penalty by up to 98%, highlighting its capacity for effectively navigating the complex design space of cross-bridged structures.

Keywords

cross-bridged hex / acoustic metamaterial / mid-low frequency / CMAES-LBFGS / sound absorption performance

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Central South University