A gear acoustic metamaterial (GAM) for broadband noise reduction is proposed. The design is optimized by a genetic algorithm to achieve structure evolution and bandgap widening. As the structure evolution proceeds, the gear acoustic metamaterial configuration evolves and the width of the first-order bandgap is widened. The bandgap width of the optimized structure is 3.55 times that of structure A, which improves the width by 658 Hz. The simulation results show that the bandgap range of the GAM with periodic boundary conditions is from 1262 to 2178 Hz. Under the time-domain transient excitation, there is an apparent acoustic wave-blocking effect in the bandgap range. The attenuation of acoustic wave transmission is evident in the bandgap range, with the average sound insulation above 20 dB and the maximum peak up to 50 dB. The sound transmission loss (STL) experimental results are basically in agreement with the STL simulation, and the actual sound insulation effect of 29.6 dB can be achieved in the bandgap band. This study provides the technical support for the modular design of gear acoustic metamaterials and broadband noise reduction.
Xing et al. (Mon,) studied this question.