Sandwich-type locally resonant acoustic metastructure with tunable bandgap

Abstract Conventional local resonance (LR) structures often require modifications in size or geometry to achieve optimal performance. This paper proposes a sandwich-type locally resonant acoustic metastructure whose bandgap can be tuned simply by adjusting the angle ratio, which enables the effective suppression of vibrations. By simply adjusting the system’s angle ratio, the value of the dynamic equivalent negative stiffness of the system is expanded by nearly 8 times. Based on the aforementioned mechanism of efficiently adjusting the equivalent negative stiffness, different angle ratios (greater than 1, equal to 1, and less than 1) were further compared, and the bandgap was broadened from 219.537 Hz (obtained at an angle ratio greater than 1 with α = 30° and β = 20°) to 527.165 Hz (achieved at an angle ratio less than 1 with α = 30° and β = 40°). At the same time, the band structure is highly consistent with the transmission spectrum, and the influence of materials and geometric parameters on the bandgap characteristics of this structure was studied. Evidently, this method of adjusting the angle ratio provides a novel insight into the development of LR structures with an ultra-wide low-frequency bandgap, and it thus has potential application value in the field of low-frequency vibration suppression.