Computational Characterization of Double Porosity Metamaterials for Broadband Sound Insulation

2017 ◽  
Author(s):  
Shichao Cui ◽  
Ryan L. Harne
Keyword(s):  
Absorption Coefficient ◽  
Transmission Loss ◽  
Functional Dependence ◽  
Double Porosity ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Low Frequencies ◽  
Static Compression ◽  
Poroelastic Media ◽  
Additional Influence

This research investigates the sound insulation properties — sound absorption coefficient and transmission loss — of a double porosity metamaterial and the functional dependence of such properties on the selection of underlying poroelastic material. The internal metamaterial geometry enables a global rotation phenomenon when the system is under a static compression. Using the finite element method, the influence of such compression upon the acoustic properties is quantified for its role in enhancing and tailoring sound insulation characteristics, while the additional influence of embedded rigid inclusions is examined. By applying these concepts to metamaterials composed from different poroelastic media, it is found that the acoustic properties can be tuned over strategic frequency ranges of relevance for sound insulation. In particular, the results demonstrate that for certain metamaterial compositions the absorption coefficient can be increased by about 100% and the transmission loss enhanced by 20% across a broad range of low frequencies by the introduction of the inclusions, while the compression constraint can increase the properties by 10 to 20% across narrow frequency bands. The outcomes suggest new possibilities for greatly enhancing the acoustic insulation properties of poroelastic materials in applications where space is limited and/or where added mass is not a concern.

scholarly journals Assessment of the Physical, Mechanical and Acoustic Properties of Arundo donax L. Biomass in Low Pressure and Temperature Particleboards

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1361
Author(s):  
Maria Teresa Ferrandez-García ◽  
Antonio Ferrandez-Garcia ◽  
Teresa Garcia-Ortuño ◽  
Clara Eugenia Ferrandez-Garcia ◽  
Manuel Ferrandez-Villena
Keyword(s):  
Particle Size ◽  
Absorption Coefficient ◽  
Transmission Loss ◽  
Raw Material ◽  
Acoustic Properties ◽  
Giant Reed ◽  
Sound Insulation ◽  
New Mineral ◽  
Particle Sizes ◽  
Insulation Material

Traditionally, plant fibres have been used as a raw material for manufacturing construction materials; however, in the last century, they have been replaced by new mineral and synthetic materials with manufacturing processes that consume a large amount of energy. The objective of this study was to determine the mechanical, physical and acoustic properties of panels made from giant reed residues. The article focuses on evaluating the acoustic absorption of the boards for use in buildings. The materials used were reed particles and urea–formaldehyde was used as an adhesive. The panels were produced with three particle sizes and the influence that this parameter had on the properties of the board was evaluated. To determine the absorption coefficient, samples were tested at frequencies ranging from 50 to 6300 Hz. The results showed that the boards had a medium absorption coefficient for the low and high frequency range, with significant differences depending on the particle size. The boards with 2–4 mm particles could be classified as Class D sound absorbers, while boards with particle sizes of 0.25–1 mm showed the greatest sound transmission loss. Unlike the acoustic properties, the smaller the particle size used, the better the mechanical properties of the boards. The results showed that this may be an appropriate sound insulation material for commercial use.

scholarly journals Non-Wovens as Sound Reducers

2018 ◽  
Vol 55 (2) ◽  
pp. 64-76
Author(s):  
D. Belakova ◽  
A. Seile ◽  
S. Kukle ◽  
T. Plamus
Keyword(s):  
Absorption Coefficient ◽  
Surface Density ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Sound Insulation ◽  
Material Structure ◽  
Sound Transmission Loss ◽  
Sound Waves ◽  
Frequency Range

Abstract Within the present study, the effect of hemp (40 wt%) and polyactide (60 wt%), non-woven surface density, thickness and number of fibre web layers on the sound absorption coefficient and the sound transmission loss in the frequency range from 50 to 5000 Hz is analysed. The sound insulation properties of the experimental samples have been determined, compared to the ones in practical use, and the possible use of material has been defined. Non-woven materials are ideally suited for use in acoustic insulation products because the arrangement of fibres produces a porous material structure, which leads to a greater interaction between sound waves and fibre structure. Of all the tested samples (A, B and D), the non-woven variant B exceeded the surface density of sample A by 1.22 times and 1.15 times that of sample D. By placing non-wovens one above the other in 2 layers, it is possible to increase the absorption coefficient of the material, which depending on the frequency corresponds to C, D, and E sound absorption classes. Sample A demonstrates the best sound absorption of all the three samples in the frequency range from 250 to 2000 Hz. In the test frequency range from 50 to 5000 Hz, the sound transmission loss varies from 0.76 (Sample D at 63 Hz) to 3.90 (Sample B at 5000 Hz).

scholarly journals Kajian Eksperimental Koefisien Redaman Akustik Bahan Pelapis Plat Dek Kapal

2018 ◽  
Vol 3 (1) ◽  
pp. 41
Author(s):  
Wibowo Harso Nugroho ◽  
Nanang J.H. Purnomo ◽  
Hardi Zen ◽  
Andi Rahmadiansah
Keyword(s):  
Absorption Coefficient ◽  
High Frequency ◽  
Transmission Loss ◽  
Base Material ◽  
Sound Insulation ◽  
Insulation Material ◽  
Base Materials ◽  
Specimen Material ◽  
Ship Classification ◽  
Technical Assessment

With the increasingly strict requirements of the ship classification bureau for permissible noise limits to allow passengers and crew to be more comfortable and secure a technical assessment is required to address the characteristics of the noise. A noise beyond the standard allowed in the vessel can be a problem to the ship operators. This noise problem will greatly affects the crews' comfort and passengers. One method to reduce the noise on a ship is to use sound insulation. This paper describes the method for determining the absorption coefficient α and the transmission loss (TL) through an acoustic test of a concrete insulation in the laboratory. The test was conducted by using the method of impedance tube where a speciment response measured by a microphone. In general, the properties of this insulation material remains as the main base material which is concrete. it has been found that the transmission loss value (TL) is in the range of 10 - 50 dB whereas for the base material the concrete is around 22 - 49 dB but the absorption coefficient α of the specimen material is much higher than the material of the base material especially in high frequency, which ranges from 0.15 to 0.97, whereas for concrete base materials have absorbent coefficient α ranges from 0.01 to 0.02.

A composite and deformable honeycomb acoustic metamaterial

2018 ◽  
Vol 32 (20) ◽  
pp. 1850204 ◽  
Author(s):  
Nansha Gao ◽  
Hong Hou ◽  
Jiu Hui Wu
Keyword(s):  
Transmission Loss ◽  
Tensile Deformation ◽  
Ethylene Vinyl Acetate ◽  
Sound Insulation ◽  
Frequency Range ◽  
Low Frequencies ◽  
Acoustic Metamaterial ◽  
Copolymer Films ◽  
Insulation Effect ◽  
Experiment Analysis

This paper reports the design of a deformable honeycomb acoustic metamaterial, which consists of honeycomb structures and ethylene-vinyl acetate (EVA) copolymer films stacked on each other. The FEA results agree well with the experiment analysis, and it is proved that the proposed structure can break the acoustic mass law below 1000 Hz. This paper reveals that dislocation, compression, and tensile deformation can regulate the sound transmission loss (STL) in a wider frequency range. It is concluded that the STL of a bilayer structure is, on average, 10 dB higher than that of a monolayer structure at low-frequencies. When the dislocation distance b = 1.5 mm, the corresponding STLs reach their maximum values. The FEA and experiment results prove that compression and tensile deformation can considerably improve the sound insulation effect. Such a deformable honeycomb acoustic metamaterial with high STL provides a new concept for engineering noise control.

scholarly journals The Effects of Various Additive Components on the Sound Absorption Performances of Polyurethane Foams

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Shuming Chen ◽  
Yang Jiang ◽  
Jing Chen ◽  
Dengfeng Wang
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Polyurethane Foams ◽  
Acoustic Properties ◽  
Acoustic Absorption ◽  
Absorption Properties ◽  
Maximum Enhancement ◽  
Flexible Polyurethane ◽  
Pu Foams

Flexible polyurethane (PU) foams comprising various additive components were synthesized to improve their acoustic performances. The purpose of this study was to investigate the effects of various additive components of the PU foams on the resultant sound absorption, which was characterized by the impedance tube technique to obtain the incident sound absorption coefficient and transmission loss. The maximum enhancement in the acoustic properties of the foams was obtained by adding fluorine-dichloroethane (141b) and triethanolamine. The results showed that the acoustic absorption properties of the PU foams were improved by adding 141b and triethanolamine and depended on the amount of the water, 141b, and triethanolamine.

scholarly journals Acoustic Properties of 316L Stainless Steel Hollow Sphere Composites Fabricated by Pressure Casting

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1047
Author(s):  
Chunhe Wang ◽  
Fengchun Jiang ◽  
Shuaiqi Shao ◽  
Tianmiao Yu ◽  
Chunhuan Guo
Keyword(s):  
Absorption Coefficient ◽  
Hollow Sphere ◽  
Sound Absorption ◽  
Random Distribution ◽  
Transmission Loss ◽  
Acoustic Properties ◽  
Sound Absorption Coefficient ◽  
Pressure Casting ◽  
Sound Transmission Loss ◽  
At Resonance

In this study, we prepared metal hollow sphere composites (MHSCs) using metal hollow spheres (MHSs) by pressure casting under vacuum conditions, and investigated the acoustic properties. The density of the MHSCs was measured using the mass to volume ratio, the microstructure of the MHSCs was observed using a scanning electron microscope, and the acoustic properties of the MHSCs were tested using an impedance tube. The measured MHSCs showed that the densities of the MHSCs with the random distribution of MHSs with diameter ~3.28 mm (1.74 g/cm3 to 1.77 g/cm3) (MHSC-3.28) were nearly equal to that of the MHSCs with the random distribution of MHSs with diameter ~5.76 mm (1.74 g/cm3 to 1.76 g/cm3) (MHSC-5.76), and lower than that of the MHSCs with the layered structure of MHSs with diameter ~3.28 mm (1.93 g/cm3 to 1.97 g/cm3) (MHSC-LS). Microstructural observations confirmed that the interface region between the MHSs and matrix demonstrated a simple physical combination pattern with pores. The acoustic properties of the MHSCs showed that the sound absorption coefficient of MHSC-LS was lower than that of MHSC-3.28 and higher than that of MHSC-5.76 at off-resonance. The sound absorption coefficient peak value of MHSC-3.28 was higher than that of MHSC-LS, and lower than that of MHSC-5.76 at resonance. The sound transmission loss of MHSC-3.28 was lower than that of MHSC-5.76, which shows the rules are independent from the resonance. The sound transmission loss of MHSC-LS was higher than that of MHSC-5.76 at resonance, but lower than that of MHSC-3.28 at off-resonance. In addition, we discuss the propagation mechanism of the sound waves in the MHSC, which is mainly determined by the distribution of the MHSs in the MHSC.

Exploration and optimization on the usage of micro-perforated panels as trim panels in commercial aircrafts

2020 ◽  
Vol 68 (1) ◽  
pp. 87-100
Author(s):  
L.I. Chenxi ◽  
H.U. Ying ◽  
H.E. Liyan
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Absorption Coefficient ◽  
Aviation Industry ◽  
Sound Insulation ◽  
Aircraft Cabins ◽  
Aircraft Cabin ◽  
Specific Frequency ◽  
Trim Panel

Micro-perforated panels (MPPs), as an alternative to porous materials for sound absorption, have been commonly used in electronic industries and aircraft engines but are barely used in aircraft cabins. The effect of MPPs on the sound insulation and absorption properties of aircraft cabin panels has been investigated in this article. Theoretical modeling has been conducted on an aircraft cabin panel structure with a trim panel replaced by an MPP trim panel, using the transfer matrix method and the classic MPP theory. It is indicated by the theoretical results that, although the sound transmission loss (STL) of the cabin panel with an MPP trim panel is lower than that with an un-perforated panel, the MPP trim panel can significantly enhance the sound absorption coefficient of the entire cabin panel structure. Based on the well-developed MPP theory, the sound absorption coefficient of an aircraft cabin panel with an MPP trim panel can be improved by optimizing the MPP's parameters at a specific frequency. Taking an engine frequency 273 Hz as an example, the optimization can increase the sound absorption coefficient to 1 by using the doublelayered MPPs. When the thermal acoustic insulation blanket is considered, although the STL of the proposed structure with double-layered MPP trim panels in a diffuse field is lower than those without MPP trim panels, the sound absorption in the cabin is significantly enhanced due to the double-layer MPP trim panel at the specific engine frequency and across all frequencies. The STL of the structure with double-layered MPP trim panels and TAIB can be higher than 40 dB from 880 Hz in a diffuse field, which implies its effectiveness as sound insulation structure in aviation industry. MPP trim panels provide a new idea for the design of aircraft cabin panels and areworthy of further research

Incorporation of Nanofiber Layers in Nonwoven Materials for Improving Their Acoustic Properties

2013 ◽  
Vol 8 (4) ◽  
pp. 155892501300800 ◽  
Author(s):  
Amir Rabbi ◽  
Hossein Bahrambeygi ◽  
Ahmad Mousavi Shoushtari ◽  
Komeil Nasouri
Keyword(s):  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Wide Band ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Sound Transmission Loss ◽  
Factors Affecting ◽  
Nonwoven Materials ◽  
Field Noise

Due to numerous developments in most industries and the increase in the usage of massive and powerful machines in every field, noise has become an unavoidable part of mechanized life and has brought about serious health hazards. The main aim of this work was to investigate the usability of polyurethane and polyacrylonitrile nanofibers for improving sound insulation properties over a wide band of frequencies and reducing weight and thickness of conventional polyester and wool nonwovens. The effect of the number of nanofiber layers and associated surface densities on acoustic properties was investigated. Sound transmission loss and sound absorption analysis using the impedance tube method were carried out as the main factors affecting acoustic behavior of samples. The results show that incorporation of nanofiber layers in nonwoven materials can improve both sound absorption and sound transmission loss simultaneously, especially in mid and lower frequencies, which are difficult to detect by conventional materials.

Low frequency acoustic properties of a honeycomb-silicone rubber acoustic metamaterial

2017 ◽  
Vol 31 (11) ◽  
pp. 1750118 ◽  
Author(s):  
Nansha Gao ◽  
Hong Hou
Keyword(s):  
Silicone Rubber ◽  
Transmission Loss ◽  
Layer Structure ◽  
Low Frequency ◽  
Sound Transmission ◽  
Honeycomb Structure ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Control Zone ◽  
Acoustic Metamaterial

In order to overcome the influence of mass law on traditional acoustic materials and obtain a lightweight thin-layer structure which can effectively isolate the low frequency noises, a honeycomb-silicone rubber acoustic metamaterial was proposed. Experimental results show that the sound transmission loss (STL) of acoustic metamaterial in this paper is greatly higher than that of monolayer silicone rubber metamaterial. Based on the band structure, modal shapes, as well as the sound transmission simulation, the sound insulation mechanism of the designed honeycomb-silicone rubber structure was analyzed from a new perspective, which had been validated experimentally. Side length of honeycomb structure and thickness of the unit structure would affect STL in damping control zone. Relevant conclusions and design method provide a new concept for engineering noise control.

scholarly journals Vibration Damping and Acoustic Behavior of PU-Filled Non-Stochastic Aluminum Cellular Solids

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 725
Author(s):  
Vitor Hugo Carneiro ◽  
Hélder Puga ◽  
José Meireles
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Polyurethane Foams ◽  
Vibration Damping ◽  
Acoustic Properties ◽  
Sound Absorption Coefficient ◽  
Cellular Solids ◽  
Infiltration Process ◽  
Wide Range

Aluminum-based cellular solids are promising lightweight structural materials considering their high specific strength and vibration damping, being potential candidates for future railway vehicles with enhanced riding comfort and low fuel consumption. The filling of these lattices with polymer-based (i.e., polyurethane) foams may further improve the overall vibration/noise-damping without significantly increasing their density. This study explores the dynamic (i.e., frequency response) and acoustic properties of unfilled and polyurethane-filled aluminum cellular solids to characterize their behavior and explore their benefits in terms of vibration and noise-damping. It is shown that polyurethane filling can increase the vibration damping and transmission loss, especially if the infiltration process uses flexible foams. Considering sound reflection, however, it is shown that polyurethane filled samples (0.27–0.30 at 300 Hz) tend to display lower values of sound absorption coefficient relatively to unfilled samples (0.75 at 600 Hz), is this attributed to a reduction in overall porosity, tortuosity and flow resistivity. Foam-filled samples (43–44 dB at 700–1200 Hz) were shown to be more suitable to reduce sound transmission rather than reflection than unfilled samples (21 dB at 700 Hz). It was shown that the morphology of these cellular solids might be optimized depending on the desired application: (i) unfilled aluminum cellular solids are appropriate to mitigate internal noises due to their high sound absorption coefficient; and (ii) PU filled cellular solids are appropriate to prevent exterior noises and vibration damping due to their high transmission loss in a wide range of frequencies and vibration damping.

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