Deep Subwavelength Broadband Sound Absorption by a Buckled Plate Resonator

Abstract

Abstract The absorption performance and the sample thickness need to satisfy the causal relation, and the sound absorption bandwidth of a thin layer structure is often very narrow to achieve high sound absorption at low frequency. In this paper, a buckled plate resonator is proposed to achieve the low frequency broadband sound absorption in the deep subwavelength range. The resonator consists of an air-tight back cavity sealed by an elastic circular thin plate. A uniform in-plane compressive force is applied on the thin plate to make the plate buckling produce negative stiffness, and the resonator operates in the pre-buckling state. By adjusting the structural stiffness, the buckled plate resonator achieves the purpose of adjusting Beff and B0, which weakens the causal principle requirement of minimum acoustic structure thickness and realizes broadband low-frequency sound absorption. The final experimental results show that one 3mm(λ/220) back cavity, 0.89 sound absorption is achieved at 515Hz, and the corresponding relative sound absorption bandwidth is 19.4%. From the causal relation, the calculated minimum sample thickness is 6.7mm for the observed absorption spectrum. Compared with traditional plate-type acoustic metamaterials, which achieve low-frequency sound absorption by increasing the mass, the absorption bandwidth is too narrow due to the influence of the quality factor Qm, our work provides a design paradigm for the low frequency broadband acoustic absorbers.