Customized acousto-mechanical metastructure for broadband low-frequency sound absorption and vibration isolation via optimization design

The demand for noise and vibration control in aerospace and vehicle manufacturing is increasing, but reliable design strategies are still lacking. Here, an integrated acousto-mechanical metastructure is proposed to realize broadband low-frequency sound absorption and vibration isolation simultaneously. Due to the introduction of bistable substructures, the proposed metastructure achieves quasi-zero stiffness vibration isolation and sound energy dissipation without external loads. Rapid customized design of the optimized metastructure is achieved by the proposed optimization algorithm. An average sound absorption coefficient of 0.8 is realized by optimization design within the frequency range of 350 Hz to 800 Hz. In addition, the proposed acousto-mechanical metastructure exhibits ultra-low broadband vibration isolation performance, with an initial isolation frequency of 40.4 Hz. Theoretical calculations, numerical simulations, and experimental results show that the acoustic performance of the metastructure benefits from the intensive mode density brought by multiple geometric degrees of freedom, while its vibration isolation performance originates from the quasi-zero stiffness beams. Overall, a multi-objective optimization method under a given structural design domain is proposed to optimize the multifunctional metastructure.