Broadband sound absorption using porous structures with embedded acoustic black holes

This paper introduces a porous structure embedded with acoustic black holes (ABHs), which not only reduces structural weight, but also significantly enhances sound absorption across a broad frequency range. At 2500 Hz, the sound absorption coefficient is increased from 0.75 to 0.99. A layered equivalent modeling approach is employed, in which a transfer matrix method connects adjacent thin layers, enabling the determination of surface acoustic impedance via a top-down method. The sound absorption coefficient is computed, and the results align well with numerical simulations, confirming the effectiveness of the design. Finite element simulations further elucidate the absorption mechanism: ABHs increase the air–porous interface, boosting viscous and thermal dissipation, while their sound-focusing effect dissipates energy at the structure’s terminal section. The simple fabrication process and lightweight design make this structure highly promising for real-world applications.