Dual-gradient multilayer ultra-microperforated panel composite for ultra-broadband and quasi-perfect sound absorption

This study proposes and experimentally validates a multilayer composite acoustic absorber based on ultra-microperforated panels with a dual-gradient configuration, incorporating decreasing pore diameters and perforation ratios across multiple layers. The innovative design achieves ultra-broadband, wide-angle, and near-perfect sound absorption, with absorption coefficients exceeding 0.98 over a wide frequency range from 2 to 20 kHz. Comprehensive performance evaluation model based on the factor Qα is established, which accounts for both the average absorption coefficient and absorption curve smoothness and demonstrates the superiority of the dual-gradient configuration compared to single-gradient or uniform designs. Simulation and experimental results reveal that the dual-gradient distribution significantly enhances acoustic impedance matching and promotes internal resonances, facilitating efficient energy dissipation. This work represents a significant advancement in the development of thin, high-performance acoustic absorbers for applications requiring broadband and wide-angle noise control.