Adjustable Low-Frequency Ultra-Wideband Sound Absorber Based on Negative Poisson's Ratio Honeycomb Structure and Quasi-Helmholtz Resonator

In recent years, acoustic metamaterials, as specially designed artificial structures, have attracted widespread attention due to their excellent performance in controlling sound waves. Compared to traditional natural materials, acoustic metamaterials exhibit significant advantages in low-frequency and ultra-wideband sound absorption applications. This study proposes a novel lightweight and tunable acoustic metamaterial for quasi-perfect absorption of underwater low-frequency and ultra-wideband sound. This metamaterial is achieved by introducing a rubber coating and embedded metal necks within Helmholtz resonators in a metallic negative Poisson's ratio honeycomb structure. Due to the phase cancellation of sound waves occurring between the quasi-Helmholtz resonator and the neck structure, the material exhibits superior acoustic performance. Theoretical predictions are in excellent agreement with finite element simulation results, further validating the effectiveness of the design. Additionally, by adjusting the geometric parameters inside the metamaterial, quasi-perfect ultra-wideband absorption was achieved within the frequency range of 302 Hz to 998 Hz, under the condition of a fixed external shape and thickness (e.g., 50 mm).