Topology optimization of embedded scatterers in wide-opening composite metamaterials for enhancing sound absorption performance

Abstract

Porous materials (PMs) typically exhibit poor sound absorption in the mid-to-low frequency range, limiting their performance in compact acoustic applications. To overcome this limitation, a geometry-constrained topology optimization framework is proposed to automatically generate a wide-opening acoustic metamaterial with embedded scatterers (AM-ES), enabling high sound absorption performance within a subwavelength thickness of only 20 mm. A variable-density method is employed to maximize the sound absorption coefficient over a targeted frequency range of 200–1500 Hz. Two distinct design domains, namely circular and rectangular configurations, are investigated to evaluate the influence of geometric constraints on the optimized microstructures. The finite element method is further employed to reveal the sound absorption mechanisms by analyzing the pressure amplitude, particle vibration velocity and energy dissipation density. Numerical results show that the optimized AM-ES significantly enhances sound absorption compared with the reference PM of identical thickness. Specifically, the optimized design obtained from the circular domain achieves broadband high absorption with α > 0.8 over a bandwidth of approximately 1050 Hz. The square arch-shaped AM-ES obtained from the rectangular design domain maintains α > 0.5 over 500–1000 Hz and peaks at 0.7 around 820 Hz. Experimental measurements using the impedance tube method confirm good agreement with numerical predictions, validating that the proposed framework provides an effective strategy for designing thin yet wide-opening AM-ESs with enhanced low-frequency sound absorption.