scholarly journals A Basic Study on a Rectangular Plane Space Sound Absorber Using Permeable Membranes

2019 ◽  
Vol 11 (7) ◽  
pp. 2185 ◽  
Author(s):  
Sakagami ◽  
Okuzono ◽  
Somatomo ◽  
Funahashi ◽  
Toyoda
Keyword(s):  
Sound Absorption ◽  
Woven Fabrics ◽  
Absorption Coefficients ◽  
Basic Study ◽  
Low Frequencies ◽  
Permeable Membrane ◽  
High Frequencies ◽  
Single Leaf ◽  
A Value ◽  
Plane Space

In this communication, the sound absorption characteristics of rectangular-shaped plane space sound absorbers without any backing structure using permeable membranes (PMs) are measured by reverberation room method. First, three types of PMs, in this study woven fabrics, are selected with different flow resistances and surface densities. They are prepared in the plane rectangular-shaped space absorbers of two different sizes. The measured results are discussed through comparison with the existing theoretical and measured results for absorbers of the other shapes or configurations. The present results and discussion demonstrate that the reverberation absorption coefficients of the proposed absorbers are low at low frequencies and converge to a moderately high value at high frequencies. Especially, ones with higher flow resistance than the air impedance converge to a value greater than 0.5, which is a theoretically estimated maximum absorption coefficient of infinite single-leaf PM. This is inferred to be attributed mainly to area effect. From these results the proposed absorbers can be used effectively despite of their very simple structure. Also it is found that the proposed absorber can offer higher sound absorption than permeable membrane absorbers of other shapes or configuration. Regarding the effect of the size, the absorbers of smaller size offer higher absorption coefficients regardless of material properties of the PMs used in the experiments.

scholarly journals Effect of Thickness, Density and Cavity Depth on the Sound Absorption Properties of Wool Boards

2018 ◽  
Vol 18 (2) ◽  
pp. 203-208 ◽  
Author(s):  
Hua Qui ◽  
Yang Enhui
Keyword(s):  
Sound Absorption ◽  
Raw Material ◽  
Wave Tube ◽  
Absorption Coefficients ◽  
Absorption Properties ◽  
Cavity Depth ◽  
Low Frequencies ◽  
High Frequencies ◽  
Standing Wave Tube ◽  
Better Than

Abstract A novel wool absorption board was prepared by using a traditional non-woven technique with coarse wools as the main raw material mixed with heat binding fibers. By using the transfer-function method and standing wave tube method, the sound absorption properties of wool boards in a frequency range of 250-6300 Hz were studied by changing the thickness, density, and cavity depth. Results indicated that wool boards exhibited excellent sound absorption properties, which at high frequencies were better than that at low frequencies. With increasing thickness, the sound absorption coefficients of wool boards increased at low frequencies and fluctuated at high frequencies. However, the sound absorption coefficients changed insignificantly and then improved at high frequencies with increasing density. With increasing cavity depth, the sound absorption coefficients of wool boards increased significantly at low frequencies and decreased slightly at high frequencies.

scholarly journals Effects of air gap, fibre type and blend ratio on sound absorption performance of needle-punched non-woven fabrics

2019 ◽  
Vol 14 ◽  
pp. 155892501984087
Author(s):  
Mlando Basel Mvubu ◽  
Rajesh Anandjiwala ◽  
Asis Patnaik
Keyword(s):  
Sound Absorption ◽  
Polyester Fibre ◽  
Natural Fibre ◽  
Woven Fabrics ◽  
Air Gap ◽  
Natural Fibres ◽  
Interactive Effects ◽  
Woven Fabric ◽  
Absorption Coefficients ◽  
Blend Ratio

This article reports a study on the effect of different natural fibres, their blend ratios and varying air gaps between a needle-punched non-woven fabric and polystyrene backing on the sound absorption coefficients of the needle-punched non-woven fabrics. These parameters as well as their interactive effects were studied by variance analysis. The air gap varied from 0 to 25 mm in 5 mm increments; three natural fibre types (agave, flax and waste wool) were used; each one blended with polyester fibres in three blending ratios. The univariate test of significance showed that all three parameters and two of the three two-way interactions effects on sound absorption coefficients were significant. Only two-way interaction effect between blend ratio and air gap on sound absorption coefficient was not significant. It was found that the sound absorption coefficients increased with an increase in air gap size up to 15 mm, after which they decreased slightly as the air gap was increased further to 25 mm. In addition, the non-woven fabrics produced from the blend of waste wool and polyester fibres achieved the highest sound absorption coefficients than those of the other two natural fibres, and generally, the sound absorption coefficients increased with the increase in polyester fibre content in each blend studied.

Sound Absorption Property of Agricultural Lignocellulsic Residue Fiber Reinforced Polymer Matrix Composites

2014 ◽  
Vol 663 ◽  
pp. 464-468 ◽  
Author(s):  
Elammaran Jayamani ◽  
Sinin Hamdan ◽  
Soon Kok Heng ◽  
Md. Rezaur Rahman
Keyword(s):  
Rice Straw ◽  
Polymer Matrix ◽  
Sound Absorption ◽  
Natural Fiber ◽  
Urea Formaldehyde ◽  
Natural Fibers ◽  
Construction Materials ◽  
Fiber Reinforced ◽  
Absorption Coefficients ◽  
Low Frequencies

In this research, the sound absorption coefficients of polymer matrix reinforced lignocellulosic fiber composites were investigated. The sound absorbing characteristic of composites was investigated in the impedance tube, according to transfer function method. A two microphone setup was fabricated according to American society for testing materials ASTM E1050-10 and it is used to measure sound absorption coefficients of composites. In this investigation, the influences of two kinds of polymer matrix (Polypropylene and Urea-formaldehyde) and two kinds of natural fibers (rice straw and kenaf) were studied for sound absorption coefficients. Four samples of novel sound absorbers were made with different matrix and fibers composition, Sample 1 and 2 was made of rice straw reinforced with polypropylene and Urea-formaldehyde and Sample 3 and 4 was made with kenaf fiber reinforced with polypropylene and Urea-formaldehyde matrix. Sound absorption coefficients were measured at frequencies from 300 Hz to 2000 Hz. The results showed when the frequencies increased, sound absorption increased until it reached a frequency of 2000 Hz but at 1200 Hz sound absorption decreased for all the samples this is due to specific character of natural fibers. From the result, the kind of natural fiber did not have significant influences on sound absorption coefficients. As results it was found that the matrix influence more in sound absorption properties in low frequencies; and due to that fact the above composites are low sound absorbing materials; but still they are better than other construction materials available in sound absorbing properties.

Comparison of multiple-layer versus multiple-cavity microperforated panels for sound absorption at low frequency

2021 ◽  
Vol 69 (4) ◽  
pp. 341-350
Author(s):  
Pedro Cobo ◽  
Francisco Simón ◽  
Carlos Colina
Keyword(s):  
Sound Absorption ◽  
Low Frequency ◽  
Single Layer ◽  
Helmholtz Resonator ◽  
Layer Versus ◽  
Low Frequencies ◽  
High Frequencies ◽  
Multiple Layer ◽  
Band Absorption ◽  
Microperforated Panels

Microperforated panels (MPPs) are recognized as suitable absorbers for noise control applications demanding special clean and health requirements.While it is relatively easy to design single-layer MPPs for sound absorption in one-to-two octave bands at medium-high frequencies, the performance for low frequencies (below 600 Hz) leads to a rather narrow-band absorption, similar to that of a Helmholtz resonator. However, multiple-layer MPPs can be designed as sound absorbers that yield low-frequency absorption in a wide frequency band. Recently, multiple-cavity perforated panels have been proposed to improve the performance of MPPs in the low-frequency range. In this article, the capability of multiple-layer and multiple-cavity MPPs to provide sound absorption at low frequencies is analyzed.

Synthesis of a multicomponent silica aerogel-containing nanocomposite for efficient sound absorption properties

2021 ◽  
pp. 096739112098574
Author(s):  
Mansoureh Hamidi ◽  
Parvin Nassiri ◽  
Homayoon Ahmad Panahi ◽  
Lobat Taghavi ◽  
Saeed Bazgir
Keyword(s):  
Silica Aerogel ◽  
Sound Absorption ◽  
Sound Pressure ◽  
Transmission Loss ◽  
Pressure Level ◽  
Tube Model ◽  
Absorption Properties ◽  
Low Frequencies ◽  
High Frequencies ◽  
Optimum Sample

In this study, the sound properties of four types of nanocomposites have been investigated. To this end, the prepared samples were measured by the impedance tube model BSWA-SW 422, SW477. It was found that the Sound Absorption Coefficient (SAC) of all samples was increased at high frequencies relatively well. The highest SAC at medium and low frequencies was related to the nanocomposite D. The results of sound Transmission Loss (TL) of nanocomposites showed that the TL value for the nanocomposite D (optimum sample) was higher at all frequencies compared to other nanocomposites. The results confirmed that adding organic and mineral materials to the silica aerogel (SA) simultaneously improves its sound properties. By measuring the Sound Pressure Level (SPL) around the enclosure without optimum sample and with optimum sample in the four sound ranges, we found that using nanocomposite D can significantly reduce the noise. According to this study, SA/polyester nonwoven layer/pan nanofibers/nanoclay nanocomposite (nanocomposites D) have great sound absorption properties, which can be used in different environments.

Numerical study of the impact of reverberation room design and test parameters on sound absorption measurements

2021 ◽  
Vol 263 (4) ◽  
pp. 2372-2383
Author(s):  
Paul Didier ◽  
Cédric Van hoorickx ◽  
Edwin Reynders
Keyword(s):  
Sound Absorption ◽  
Numerical Study ◽  
Plane Waves ◽  
Sound Field ◽  
Analysis Model ◽  
Absorption Coefficients ◽  
Low Frequencies ◽  
Room Design ◽  
The Impact ◽  
Absorption Measurements

The measurement of sound absorption in reverberation rooms following the ISO 354:2003 standard relies on Sabine's equation to derive absorption coefficients from reverberation times. This equation assumes perfect diffusivity, i.e. the sound field is composed of many statistically independent plane waves with uniformly distributed spatial phases, themselves uncorrelated to the corresponding amplitudes. In this work, both existing and fictitious reverberation rooms are numerically modelled using the finite element method. Finite porous absorbers are introduced in the rooms as equivalent fluid models. Standardized sound absorption measurement are simulated in the rooms through the determination of reverberation times. The respective effects of the sample size, sample placement, source positioning, and presence of finite panel diffusers are investigated. The resulting absorption coefficients are then confronted to the theoretical values in a perfectly diffuse sound field, that interacts with a baffled, finite-sized absorber, as obtained with a hybrid deterministic-statistical energy analysis model. The process notably underlines the strong, yet often disregarded, beneficial effect of panel diffusers at low frequencies in highly regularly-shaped rooms. Another conclusion of this work is that reverberation room design represents a crucial factor that can influence sound absorption measurements at low frequencies.

Mesomorphic and dielectric properties of esters useful for formulation of nematic mixtures for dual frequency addressing system

2009 ◽  
Vol 17 (1) ◽  
Author(s):  
D. Ziobro ◽  
P. Kula ◽  
J. Dziaduszek ◽  
M. Filipowicz ◽  
R. DĄbrowski ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Homologous Series ◽  
Strong Dependence ◽  
Dielectric Anisotropy ◽  
Dual Frequency ◽  
Low Frequencies ◽  
High Frequencies ◽  
Smectic A ◽  
Smectic C ◽  
A Value

AbstractMesomorphic and dielectric properties of three homologous series of two and three ring fluorosubstituted esters are described. They are 4-cyano-3-fluorophenyl 4-alkyloxy-2-fluorobenzoates, 4-cyano-3-fluorophenyl 4-(4-alkylbenzoyloxy)-2-fluorobenzoates and 3-fluoro-4-cyanophenyl, or 3-fluoro-4-isothiocyanatophenyl or 3,4-difluorophenyl 4′-alkyl-2,3-difluoro-biphenyl-4-carboxylates. The compounds exhibit the nematic mesophase accompanied by the smectic A or smectic C mesophase in some cases. Most of them show strong dependence of the dielectric anisotropy Δε upon frequency, at low frequencies Δε reaches a value ∼200, while at high frequencies a small negative dielectric anisotropy appears.

scholarly journals Application of Paper Folding Technique to Three-Dimensional Space Sound Absorber with Permeable Membrane: Case Studies of Trial Productions

2020 ◽  
Vol 25 (2) ◽  
pp. 243-247 ◽  
Author(s):  
Kimihiro Sakagami ◽  
Takeshi Okuzono ◽  
Hirotaka Suzuki ◽  
Nao Koyanagi ◽  
Masahiro Toyoda
Keyword(s):  
Dimensional Space ◽  
Three Dimensional ◽  
Woven Fabrics ◽  
Shell Shape ◽  
Pilot Studies ◽  
Permeable Membrane ◽  
High Frequencies ◽  
Sound Absorber ◽  
Paper Folding ◽  
Suitable Form

The authors propose a space sound absorber made of a permeable membrane (PM), including woven or non-woven fabrics in three-dimensional shapes, e.g., cylinder, rectangle, etc. The proposed absorbers are examined by experimental measurements and boundary element analyses, and it is found that they can be effectively used especially for middle and high frequencies. In order to develop these absorbers for wider applications, it would be desirable to give them additional values and functions, particularly to elaborate on their design. Supposing that they could also be used for lighting equipment, such as lampshades as one of the applications, pilot studies on pseudo-cylindrical, and pseudo-spherical PM space absorbers with uneven surfaces produced by paper-folding (origami technique) are carried out. The pseudo-cylindrical concave curves (PCCC) shell shape has been proven as a suitable form for a lampshade, and the pseudo-spherical concave curves (PSCC) shell shape is an application of PCCC. In this paper, PCCC and PSCC shell shapes are applied to three-dimensional PM space absorbers, and trials are conducted using PMs selected by flow resistance measurements and preliminary simulations. The sound absorptivity of the specimens is measured in a reverberation chamber, and their absorptivity is 0.6 (PCCC case) and 0.4 (PSCC case) at mid-high frequencies.

scholarly journals Dual UV-Thermal Curing of Biobased Resorcinol Epoxy Resin-Diatomite Composites with Improved Acoustic Performance and Attractive Flame Retardancy Behavior

2021 ◽  
Vol 2 (1) ◽  
pp. 24-48
Author(s):  
Quoc-Bao Nguyen ◽  
Henri Vahabi ◽  
Agustín Rios de Anda ◽  
Davy-Louis Versace ◽  
Valérie Langlois ◽  
...  
Keyword(s):  
Heat Release ◽  
Flame Retardant ◽  
Epoxy Resin ◽  
Flame Retardancy ◽  
Sound Absorption ◽  
Flexural Modulus ◽  
Construction Materials ◽  
Acoustic Properties ◽  
Low Frequencies ◽  
Compacting Pressure

This study has developed novel fully bio-based resorcinol epoxy resin–diatomite composites by a green two-stage process based on the living character of the cationic polymerization. This process comprises the photoinitiation and subsequently the thermal dark curing, enabling the obtaining of thick and non-transparent epoxy-diatomite composites without any solvent and amine-based hardeners. The effects of the diatomite content and the compacting pressure on microstructural, thermal, mechanical, acoustic properties, as well as the flame behavior of such composites have been thoroughly investigated. Towards the development of sound absorbing and flame-retardant construction materials, a compromise among mechanical, acoustic and flame-retardant properties was considered. Consequently, the composite obtained with 50 wt.% diatomite and 3.9 MPa compacting pressure is considered the optimal composite in the present work. Such composite exhibits the enhanced flexural modulus of 2.9 MPa, a satisfying sound absorption performance at low frequencies with Modified Sound Absorption Average (MSAA) of 0.08 (for a sample thickness of only 5 mm), and an outstanding flame retardancy behavior with the peak of heat release rate (pHRR) of 109 W/g and the total heat release of 5 kJ/g in the pyrolysis combustion flow calorimeter (PCFC) analysis.

scholarly journals Sound absorption behavior of woven fabrics as micro perforated panel absorber

2021 ◽  
Vol 1896 (1) ◽  
pp. 012003
Author(s):  
Gunawan ◽  
I Prasetiyo ◽  
D R Adhika ◽  
F Brahmana ◽  
B Yuliarto
Keyword(s):  
Sound Absorption ◽  
Woven Fabrics ◽  
Panel Absorber
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