Low-frequency broadband sound absorption in a parallel truncated-tail sonic black hole

Objective This study systematically investigates the acoustic characteristics of low-frequency broadband parallel truncated-tail sonic black holes (TSBH) absorbers, with a particular focus on their broadband sound absorption performance. Using an integrated approach that combines theoretical analysis, numerical simulation, and experimental validation, the research thoroughly examines the sound absorption mechanisms and energy dissipation properties of this innovative structure. The findings offer a novel technical solution to the challenges of low-frequency noise absorption.

Method This study systematically investigates the influence of structural parameters on the acoustic performance of TSBH based on their sound absorption mechanism. By incorporating the design concept of parallel acoustic metamaterials, an innovative parallel TSBH structure with multiple configurations was developed. The effective medium method was employed to calculate the equivalent acoustic parameters of 2D TSBH structures, and finite element simulation was used to validate the calculations. The absorption mechanism was explored from the perspective of slow sound effects. Comprehensive parameter scanning revealed the influence of key parameters, including lattice number, lattice constant, truncation height, and power-law exponent, on absorption performance. The low-frequency broadband sound absorption performance of TSBH was designed based on theoretical analysis and numerical simulations. Impedance tube measurements confirmed the structure's outstanding low-frequency broadband absorption characteristics.

Results Numerical simulations demonstrate that the effective parameters, including sound velocity, density, and bulk modulus, derived from the effective medium method, can accurately predict the acoustic impedance and absorption performance of truncated acoustic black hole. The sound absorption mechanism of TSBH primarily originates from the air resonance phenomenon within their structure. Parameter optimization showed that the quadratic TSBH configuration exhibits optimal low-frequency broadband absorption within the test range. Numerical results demonstrate that key structural parameters significantly influence the material's sound absorption performance. Systematic optimization and coordinated adjustment of these parameters are crucial for achieving high-efficiency broadband absorption in the low frequency range. Experimental data verified that the parallel structure achieves an average absorption coefficient of 0.72 in the 250−1 600 Hz band, thanks to multi-band synergistic effects. This represents nearly a two-fold improvement over single-unit structures.

Conclusion This study theoretically and experimentally demonstrates the feasibility of applying parallel acoustic metamaterial design principles to truncated-tail sonic black holes. The results reveal that the designed parallel truncated-tail sonic black hole absorber exhibits exceptional low-frequency broadband absorption characteristics. With its unique performance advantages, it provides an innovative solution for low-frequency noise control and demonstrates significant potential for practical applications.