Enhancing the Sound Absorption Effect of Granular Absorbers Through Optimized Configuration

In recent years, significant research attention has been directed toward the sound absorption properties of granular materials, owing to their inherently reconfigurable and tunable microstructural characteristics. The present study aims to enhance the sound absorption performance of granular materials by optimizing their structural configuration, i.e., by introducing two distinct pore scales into the granular medium. First, theoretical models describing the acoustic behavior of randomly close-packed spherical beads are extended and experimentally validated. Second, for double-layer structures, improved absorption efficiency within targeted frequency bands is achieved through selection and arrangement of bead sizes, while the influence of layer thickness and bead diameter is examined. It is found that, under a designated total sample thickness, specific layer thickness ratios are essential for achieving optimal broadband sound absorption. Finally, for perforated samples, the low-frequency sound absorption capacity is enhanced by appropriately selecting bead and perforation parameters, with the influence of perforation diameter on both the peak frequency and sound absorption coefficient analyzed. This work provides a practical and supportive framework for designing and optimizing high-performance granular acoustic materials.