Numerical analysis and experimental study of membrane-type acoustic metamaterial plate with X-shaped pendulum arm and cylindrical mass blocks

Abstract

Membrane-type acoustic metamaterials have a favorable noise suppression effect. Hence, a membrane-type acoustic metamaterial plate (MAML) with an X-shaped pendulum arm and cylindrical mass blocks (CMB) was proposed in this paper. The theoretical model based on spring–mass systems and numerical simulation models of the membrane-type acoustic metamaterial cell (MAMC) were established under fixed and periodic boundary conditions to reveal the noise attenuation mechanism quantitatively, and the necessity of the CMB is discussed. Based on the results, it can be observed that the normal displacement of the membrane is nearly zero when the noise frequency is at the peak of the sound transmission loss (STL) curve. However, when the frequency is at the valley of the STL curve, the displacement is nonzero and fluctuates significantly. Meanwhile, by comparing the STL curves with and without the CMB, it was found that the MAMC performance is improved effectively by the CMB at low frequencies. The effective mass density of MAMC was found to be negative. To verify the accuracy of numerical calculations, an impedance tube experiment was conducted. Finally, orthogonal experiments were designed to describe the effects of the structural parameters a, l, and t on the effective bandwidth [Formula: see text], peak frequency [Formula: see text], and comprehensive index [Formula: see text] and to obtain the optimal structural parameter combinations for different indexes. This work further contributes to applying and developing the membrane-type acoustic metamaterial.