Design and Optimization of an Enhanced Sonic Black Hole Structure for Low-Frequency Broadband Sound Absorption

Abstract

Here, an enhanced sonic black hole (ESBH) structure is proposed to achieve efficient low-frequency broadband sound absorption. The ESBH design features a conical cavity formed by a bilaterally tapered power-law profile and incorporates porous material filling to enhance acoustic energy dissipation, particularly in the low-frequency range where conventional sonic black hole structures are limited by weak air damping. The theoretical foundation is established using a transfer matrix method that accounts for the modified wave number induced by the porous medium. The model is validated numerically and employed to investigate the influence of key structural parameters on the absorption coefficient. To further enhance performance, a hybrid optimization strategy is utilized that combines a backpropagation neural network with an improved grasshopper optimization algorithm. The optimized structure exhibits superior sound absorption and transmission loss characteristics while minimizing overall volume. Experimental verification demonstrates that the proposed ESBH structure outperforms traditional designs in terms of low-frequency acoustic performance, indicating strong potential for practical noise reduction applications.