Locally resonant metamaterials with multimodal resonators for sound insulation improvement

Locally resonant metamaterials are used to increase the sound insulation of a host structure, by introducing bandgaps for wave propagation. While most solutions employ periodic layouts with translational resonators, this work investigates the potential of rotational and multimodal resonators. A comprehensive analytical model of sound insulation, based on dynamic effective mass density, is first presented. It is then demonstrated how multimodal locally resonant metamaterials can suppress the broad coincidence dip in the diffuse transmission loss of orthotropic host plates, and the geometry of two realizable multimodal resonators is optimized to maximize broadband sound insulation.