Vibration and Noise Reduction Characteristics of a Coated Truncated Cone Acoustic Metamaterial with Local Resonance for Low-Frequency Bandgap

For effectively suppressing low-frequency vibration and noise and broaden the elastic wave bandgap, a coated truncated cone structure metamaterial for low-frequency broadband characteristics is designed based on the local resonance mechanism. The bandgap width is derived by combining the mass-spring equivalent model and the equivalent dynamic mass method. The band structure of the acoustic metamaterial is calculated by the Finite Element Method (FEM) to investigate the formation mechanisms of the band gaps and to systematically study the influence of the resonant unit’s geometric and material parameters on the bandgap characteristics. The vibration transfer function and sound transmission loss are also calculated. Finally, laser scanning vibration tests and acoustic impedance tube sound insulation experiments are employed to verify the theoretical and simulation results, and good agreements are obtained. The main results are: (1) The coated truncated cone structure metamaterial exhibits a low-frequency broadband bandgap ranging from 210[Formula: see text]Hz to 336[Formula: see text]Hz, with a bandwidth of 126[Formula: see text]Hz. (2) With the decrease of lattice constant, the increase of density of scatterer and the increase of filling factor, the bandgap lower frequency shifts to low frequency and the bandwidth increases. (3) Within the bandgap range, the metamaterial plate achieves a maximum vibration transmission loss of 58[Formula: see text]dB and an improvement of up to 19.3[Formula: see text]dB in sound insulation performance. The findings of this research provide valuable guidance for the design of metamaterials tailored for low-frequency vibration and noise control, underscoring its potential for practical engineering applications.