Optimization of Sound Absorption and Insulation Performances of a Dual-Cavity Resonant Micro-Perforated Plate

This study investigates a dual-cavity resonant composite sound-absorbing structure based on a micro-perforated plate.Using the COMSOL impedance tube model,the effects of various structural parameters on sound absorption and sound insulation performances are analyzed.Results show that the aperture of the micro-perforated plate has the greatest influence on the sound absorption coefficient;the smaller the aperture,the greater is this coefficient.The thickness of the resonance plate has the most significant influence on the sound insulation and resonance frequency;the greater the thickness,the wider the frequency domain in which sound insulation is obtained.In addition,the effect of filling the structural cavity with porous foam ceramics has been studied,and it has been found that the porosity and thickness of the porous material have a significant effect on the sound absorption coefficient and sound insulation,while the pore size exhibits a limited influence.

Sound Insulation Performance of Structural Wood Wall Integrated with Wood Plastic Composite

The sound insulation performance is an important technical index for evaluating the physical property of the building wall.Three kinds of structural wood walls integrated with wood plastic composite(WPC)were designed.And the sound insulation performance of the walls was studied.The results showed that for the wall that constructed by the WPC as the wall studs,compared with the one that constructed by the pine wood as the wall studs,the deviation of their sound insulation was lower than±3 dB.The wall’s external panel material had significant effect on the wall’s sound insulation property,and the contribution of the wood-plastic panel to the sound insulation was much higher than that of the polyvinyl chloride(PVC)plastic hanging board.The surrounding sealing quality of the wall’s external panel material had an important influence on the sound insulation effect of the building wall,and the panel of the wood plastic interior wall had less influence on the sound insulation performance of the wall.Taking the sound-absorbing cotton or non-woven fabric as elastic strips was an effective technical measure to improve the sound insulation performance of the walls.The sound insulation was improved by 2.4 dB and 3.1dB respectively after the correction of pink noise spectrum,and increased by 2.8 dB and 3.6 dB respectively after the correction of traffic noise spectrum.

Analysis of Soundproof Technology of Assembled Steel Structure Houses

The problem of noise has always been highlighted in assembled steel structure houses.Therefore,it is necessary to use effective soundproof measures where steel beams intersect with the reserved line pipe openings,doors,windows,elevator shafts,and other locations.In this paper,we will investigate the areas with subpar soundproof performance in an assembled steel structure residential project and propose suitable noise control measures to address this issue.

Symplectic analysis for elastic wave propagation in two-dimensional cellular structures

On the basis of the finite element analysis, the elastic wave propagation in cellular structures is investigated using the symplectic algorithm. The variation principle is first applied to obtain the dual variables and the wave propagation problem is then transformed into two-dimensional （2D） symplectic eigenvalue problems, where the extended Wittrick-Williams algorithm is used to ensure that no phase propagation eigenvalues are missed during computation. Three typical cellular structures, square, triangle and hexagon, are introduced to illustrate the unique feature of the symplectic algorithm in higher-frequency calculation, which is due to the conserved properties of the structure-preserving symplectic algorithm. On the basis of the dispersion relations and phase constant surface analysis, the band structure is shown to be insensitive to the material type at lower frequencies, however, much more related at higher frequencies. This paper also demonstrates how the boundary conditions adopted in the finite element modeling process and the structures＇ configurations affect the band structures. The hexagonal cells are demonstrated to be more efficient for sound insulation at higher frequencies, while the triangular cells are preferred at lower frequencies. No complete band gaps are observed for the square cells with fixed-end boundary conditions. The analysis of phase constant surfaces guides the design of 2D cellular structures where waves at certain frequencies do not propagate in specified directions. The findings from the present study will provide invaluable guidelines for the future application of cellular structures in sound insulation.

Low frequency acoustic properties of bilayer membrane acoustic metamaterial with magnetic oscillator

A bilayer membrane acoustic metamaterial was proposed to overcome the influence of the mass law on traditional acoustic materials and obtain a lightweight thin-layer structure that can effectively isolate low frequency noise. The finite element analysis（FEA） results agree well with the experimental results.It is proved that the sound transmission losses（STLs） of the proposed structures are higher than those of same surface density acoustic materials. The introduction of the magnetic mass block is different from the traditional design method, in which only a passive mass block is fixed on the membrane. The magnetic force will cause tension in the membrane, increase membrane prestress, and improve overall structural stiffness. The effects of the geometry size on the STLs are discussed in detail. The kind of method presented in this paper can provide a new means for engineering noise control.

Numerical Simulation and Experimental Study of Underwater Compound Structures Containing Honeycomb Interlayer

Honeycomb interlayer structure sound wave transferring theory of infinite is introduced into the underwater noise control. Based on the layered elastic or viscoelastic medium, the sound insulation property of a normal incidence plane wave on underwater honeycomb interlayer structure is studied by using the method of the transfer matrix and percentage distribution of sound energy in As a particular kind of complex multilayered rubber compound structures, honeycomb different areas. compound structure has better sound insulation property than rubber interlayer with cylindrical cavities compound structure. Simulation results show that the property of rubber material has great effect on structural sound insulation. Soft and small Poisson＇ s ratio rubber can obviously improve sound insulation performance of the whole structure. Furthermore, the material property of the face layer of the honeycomb interlayer structure has greater effects on the insulation performance. To validate the theoretical analysis, large samples of freedom-field measurement of honeycomb sandwich compound structure is carried out in the anechoic water tank of our university. The measurement result is in good agreement with the theoretical prediction.

Acoustic properties of closed-cell aluminum foams with different macrostructures

As structural materials, closed-cell aluminum foams possess obvious advantages in product dimension, strength and process economics compared with open cell aluminum foams. However, as a kind of structure-function integration materials, the application of closed-cell aluminum foams has been restricted greatly in acoustic fields due to the difficulty of sound wave penetration. It was reported that closed-cell foams with macrostructures have important effect on the propagation of sound waves. To date, the relationship between macrostructures and acoustic properties of commercially pure closedcell aluminum foams is ambiguous. In this work, different perforation and air gap types were designed for changing the macrostructures of the foam. Meanwhile, the effect of macrostructures on the sound absorption coefficient and sound reduction index were investigated. The results showed that the foams with half-hole exhibited excellent sound absorption and sound insulation behaviors in high frequency range（〉2500 Hz）. In addition, specimens with air gaps showed good sound absorption properties in low frequency compared with the foams without air gaps. Based on the experiment results, propagation structural models of sound waves in commercially pure closed-cell aluminum foams with different macrostructures were built and the influence of macrostructures on acoustic properties was discussed.