Acoustic metamaterial plates with grid-stiffened surfaces for mid-to-low frequency sound insulation

A type of acoustic metamaterial plates with grid-stiffened surfaces is proposed, and its mid-to-low frequency sound insulation performance is investigated theoretically, numerically and experimentally in this paper. A key contribution is the introduction of the dynamic effective areal density (DEAD) as a fundamental predictive parameter. Unlike static mass, the DEAD quantifies the effective inertial mass participating in local resonance, directly linking structural dynamics to sound insulation. And the DEAD of the metamaterial plates is derived and analyzed based on the periodicity of the whole structure and the simplified model of the structural unit. This enables the establishment of a theoretical relationship between the design parameters and the sound transmission loss (STL) of the metamaterial plates around the local resonance frequencies, which is demonstrated experimentally. The experimental STL peak frequency agrees well with both the theoretical predictions and the finite element method (FEM) simulations. The frequency range of enhanced sound insulation from theoretical predictions is in close agreement with the band gaps obtained from the simulated band structure. The results would provide guidance and support for the solution design of sound barriers, especially for their sound insulation improvement in vehicle body panels or aircraft cabins.