Novel three-dimensional acoustic metamaterials with low-frequency bandgap and strong vibration and noise attenuation

The suppression of low-frequency vibration and noise has been the research focus of acoustic metamaterials. Based on the local resonance effect of the subwavelength structure, two new topology optimization methods are proposed in this paper, and two new three-dimensional single-phase material structures are obtained. Based on Bloch theorem and lattice theory, finite element simulations of the single cells with different structures are carried out to analyze and explore the bandgap properties and opening mechanism of the structures. The frequency response spectra are obtained by vibrational transport simulation of the finite-period structures. The results show that both novel metamaterial structures have good bandgap properties, the widest first bandgap width within 2000 Hz reaches 809 Hz, and the total bandgap width percentage reaches 52.7 %, and the main vibration forms of opening the bandgap are rotational and offset resonance of the internal structure and torsional resonance of part of the structure.