Investigation on low-frequency broadband perfect sound absorption metastructure based on area coupling effect
Liangfei Ding, Lihua Tang, Baozhu Cheng, Longxu Wang, Rui Li, Hong Hou
Abstract
Abstract To Address the issue of broadband perfect sound absorption failure caused by area coupling effects in acoustic metamaterials, particularly during transitions from narrowband to broadband, this study proposes a novel structure termed ‘bending channel Helmholtz coupled sound absorber’ (BCSA), which considers the area coupling effect. First, theoretical models for the bending channels and Helmholtz resonator (HR) structures are developed using the thermal viscoelastic equivalent theory. Finite element analysis is then employed to validate the accuracy of these models. Based on the aforementioned models, the influence of the geometric parameters of the HR and bending channels on acoustic absorption performance is systematically investigated. Considering both geometric parameter tuning and the area coupling effects among units, a theoretical model of the BCSA composed of multiple bending channels and HR units is constructed. An optimized design of a BCSA metastructure with a thickness of only 35 mm exhibits an absorption coefficient exceeding 0.8 within the frequency range of 288–365 Hz. Subsequently, the mechanisms underlying the high-performance low-frequency broadband absorption of the BCSA metastructure are analyzed using finite element simulations, confirming the validity of the theoretical model. Finally, a 35-mm-thick BCSA sample is fabricated using 3D printing . Impedance tube experiments demonstrate that the optimized BCSA attains an absorption coefficient above 0.8 across the frequency range of 294–364 Hz.Compared with existing bending channels or HR metamaterials, this study transforms the detrimental area coupling side effects into a design advantage. While traditional methods achieve bandwidth broadening by increasing the number or thickness of units, often causing impedance mismatches the BCSA leverages impedance increments generated by parallel non-ideal units to counterbalance each unit’s intrinsic loss. The study clarifies the role of area coupling in sound absorption, offering theoretical insights for mitigating excessive loss damage in multi-unit coupling and offering guidance for the design of low-frequency broadband perfect sound absorption metamaterials.