Resonant modal group theory of membrane-type acoustical metamaterials for low-frequency sound attenuation

Abstract

In order to overcome the influence of the structural resonance on the continuous structures and obtain a lightweight thin-layer structure which can effectively isolate the low-frequency noises, an elastic membrane structure was proposed. In the low-frequency range below 500 Hz, the sound transmission loss (STL) of this membrane type structure is greatly higher than that of the current sound insulation material EVA (ethylene-vinyl acetate copo) of vehicle, so it is possible to replace the EVA by the membranetype metamaterial structure in practice engineering. Based on the band structure, modal shapes, as well as the sound transmission simulation, the sound insulation mechanism of the designed membrane-type acoustic metamaterials was analyzed from a new perspective, which had been validated experimentally. It is suggested that in the frequency range above 200 Hz for this membrane-mass type structure, the sound insulation effect was principally not due to the low-level locally resonant mode of the mass block, but the continuous vertical resonant modes of the localized membrane. So based on such a physical property, a resonant modal group theory is initially proposed in this paper. In addition, the sound insulation mechanism of the membrane-type structure and thin plate structure were combined by the membrane/plate resonant theory.

Polarized pass band for longitudinal waves in solid phononic crystals

“…Visualizing the eigenstates is important for understanding the wave modes. On the other hand it has been an effective tool for analyzing the mechanism of the formation of band gaps in PCs [2,3,25,26,29,46] and AMMs [1,[4][5][6][7][8]47]. Figure 2 illustrates the mode shapes of the five points marked as A-E that are located on the lowest three branches in figure 1(c).…”

“…Much research has been conducted in recent years on the propagation of elastic waves in periodic materials known as phononic crystals (PCs) or acoustic metamaterials (AMMs). They have man-made structures exhibiting extraordinary properties which surpass conventional materials found in nature, such as outstanding sound insulation performance [1,2], negative elastic parameters [3][4][5][6][7][8], self-collimation [9], and superlensing [10][11][12]. PCs are composite structures that are usually composed of two or more kinds of periodically arranged conventional materials whose elastic properties are distinct from one another, such as metals and plastics.…”

Material Parameters Acquisition and Sound Insulation Performance analysis of Membrane-type Acoustic Metamaterials Applied for Transformer

“…In 2010, Naify et al studied the influence of additional weight mass and film tension on the sound insulation range of thin-film acoustic metamaterial by impedance tube test and finite element simulation, and carried out a series of dynamic analysis on the resonance frequency and film vibration at the peak of sound insulation using laser vibration testing instruments [4]. From the research progress of acoustic metamaterials [5][6][7][8], we find that the focus of research on acoustic metamaterials is the effective parameters of materials, and the parameters directly affect the sound insulation effect [9][10][11][12]. In this paper, we mainly study the sound insulation characteristics of thin-film acoustic metamaterial composed of rigid frame, flexible film and additional mass.…”

Ultrathin lightweight plate-type acoustic metamaterials with positive lumped coupling resonant

“…By employing minimal rigidity of the elastic membrane, the low-frequency sound attenuation and other novel properties could be obtained. [1][2][3][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Since only the narrowband sound attenuation is achieved by the earliest membrane-type acoustic metamaterial structures, 13 a sought-after motivation is to design the structures with broadband strong sound attenuation ability. For example, Yang et al 2 had achieved broadband insulation by stacking multiple layers arrays in series, 1 while Naify et al 19 and Zhang et al 22 realized the multipeaks sound transmission loss (STL) profile by coaxial ring mass or single-layer multiple cells arrays.…”

“…In this context, we have given a scheme to reduce the tension dependence by increasing the membrane thickness for improving the stability of acoustical performance. 14,15 Actually, the tension dependence feature can also be eliminated by using the materials with higher Young's modulus to replace the soft rubber. However, the rigidity of plates are several orders higher than that of soft rubber membranes, which makes the design of the locally resonant structures using the stiff plates for low frequency sound attenuation to be difficult.…”