A review on innovative measures for improving the sound absorption of acoustic materials for broader frequency ranges.

This review focuses on various acoustic materials engineered to enhance sound absorption across different frequency ranges, emphasizing their properties, measurement methods, and applications. Porous materials like polyurethane foams and natural fibers are effective for mid to high-frequency absorption, while resonator-based structures such as Helmholtz resonators and micro-perforated panels target low-frequency sounds. Advanced acoustic metasurfaces and composite materials combine multiple mechanisms to achieve broader and tunable absorption spectra. Experimental techniques (e.g., impedance tube, reverberation room) and simulation methods (e.g., finite element analysis, ray tracing) are used to evaluate sound absorption coefficients and optimize material performance. The review highlights sustainable alternatives, material modifications, and hybrid designs as key strategies to address challenges in noise control for architectural, industrial, automotive, and underwater stealth applications.