Topology optimization for locally resonant sonic materials

This Letter presents an optimal design method for locally resonant sonic materials using topology optimization incorporating a level-set method. Examples demonstrate that this method provides optimal configurations that exhibit roughly hundred-fold acoustic attenuation at desired frequencies, evaluated using frequency analyses of displacements at the output side of the design domain. We also explore the effects on the acoustic response of combining two optimal configurations. Our results indicate that the proposed method can be applied for the design of locally resonant sonic materials that have multiple attenuation peaks in a combined configuration. Additionally, we analyze eight configuration combinations, one consisting of eight identical configurations and the other of eight slightly different unit cells. The results show the combination of eight slightly different optimal configurations achieves a wider frequency range of attenuation.