scholarly journals Investigation of Sound Absorption Properties of Heat-Treated Indonesian Momala (Homalium foetidum (Roxb.) Benth.) and Korean Red Toon (Toona sinensis (A. Juss.) M. Roem.) Cross Sections

Forests ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1447
Author(s):  
Eun-Suk Jang ◽  
Chun-Won Kang
Keyword(s):  
Heat Treatment ◽  
Absorption Coefficient ◽  
Pore Size ◽  
Cross Sections ◽  
Sound Absorption ◽  
Gas Permeability ◽  
Sound Absorption Coefficient ◽  
Absorption Function ◽  
Toona Sinensis ◽  
Heat Treated

This study investigates the effects of heat treatment time and presence of an air back cavity on the sound absorption performance of Indonesian momala (Homalium foetidum (Roxb.) Benth.) and Korean red toon (Toona sinensis (A. Juss.) M. Roem.) cross sections. To examine the porous characteristics of the two species before and after heat treatment, gas permeability, pore size, and porosity analyses were conducted. Additionally, the sound absorption coefficient was measured based on various heat treatment times and air back cavity sizes. The results showed that, with heat treatment at 210 °C for 6 h, the gas permeability improved by 4.3% for the momala and 38.5% for the red toon, the maximum pore size was improved by 5.25% in the momala and 26.0% in the red toon, and the through-pore porosity improved by 22.7% for the momala and 117.0% for the red toon. Due to these pore structure changes, the noise reduction coefficient (NRC) of the heat-treated momala improved by 6.8%. When a 3-cm air back cavity was applied to the heat-treated momala, the NRC was improved to 92.5%. Similarly, when the same air back cavity was applied to the heat-treated red toon, the NRC was improved to 190.7%. This study demonstrated that an increase in pore size and through-pore porosity by heat treatment triggered an increase in the sound absorption coefficient. Additionally, when an air cavity was applied, the sound absorption coefficient of both heat-treated wood species was increased at low frequency. From the results of this study, we expected that heat-treated momala and red toon cross-sections can be utilized as eco-friendly ceiling materials with sound absorption function.

scholarly journals Air permeability and sound absorption coefficient changes from ultrasonic treatment in a cross section of Malas (Homalium foetidum)

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Chun-Won Kang ◽  
Eun-Suk Jang ◽  
Nam-Ho Lee ◽  
Sang-Sik Jang ◽  
Min Lee
Keyword(s):  
Absorption Coefficient ◽  
Ultrasonic Treatment ◽  
Sound Absorption ◽  
Gas Permeability ◽  
Treated Wood ◽  
Untreated Wood ◽  
Sound Absorption Coefficient ◽  
Permeability Constant ◽  
Average Value ◽  
Permeability Increase

AbstractWe investigated the effect of ultrasonic treatment on Malas (Homalium foetidum) gas permeability and sound absorption coefficient using the transfer function method. Results showed a longitudinal average Darcy permeability constant of 2.02 (standard deviation SD 0.72) for untreated wood and 6.15 (SD 3.07) for ultrasound-treated wood, a permeability increase of 3.04 times. We also determined the average sound absorption coefficients in the range of 50 to 6.4 kHz and NRC (noise reduction coefficient: average value of sound absorption coefficient value at 250, 500, 1000, and 2000 Hz) of untreated Malas. Those values were 0.23 (SD 0.02) and 0.13 (SD 0.01), respectively, while those of ultrasonic-treated Malas were 0.28 (SD 0.02) and 0.14 (SD 0.02), a 19.74% increase in average sound absorption coefficient.

Sound Absorption Characteristics of Porous Steel Manufactured by Lost Carbonate Sintering

2009 ◽  
Vol 1188 ◽  
Author(s):  
Miao Lu ◽  
Carl Hopkins ◽  
Yuyuan Zhao ◽  
Gary Seiffert
Keyword(s):  
Absorption Coefficient ◽  
Pore Size ◽  
Sound Absorption ◽  
Single Layer ◽  
Normal Incidence ◽  
Sound Absorption Coefficient ◽  
Absorption Coefficients ◽  
Impedance Tube ◽  
Absorption Characteristics

AbstractThis paper investigates the sound absorption characteristics of porous steel samples manufactured by Lost Carbonate Sintering. Measurements of the normal incidence sound absorption coefficient were made using an impedance tube for single-layer porous steel discs and assemblies comprising four layers of porous steel discs. The sound absorption coefficient was found not to vary significantly with pore size in the range of 250-1500 μm. In general, the absorption coefficient increases with increasing frequency and increasing thickness, and peaks at specific frequencies depending on the porosity. An increase in porosity tends to increase the frequency at which the sound absorption coefficient reaches this peak. An advantage was found in using an assembly of samples with gradient porosities of 75%-70%-65%-60% as it gave higher and more uniform sound absorption coefficients than an assembly with porosities of 75%.

Sound Absorption Behavior of Porous Al Produced by Spacer Method

2006 ◽  
Vol 15-17 ◽  
pp. 422-427
Author(s):  
Tetsumune Kuromura ◽  
Masataka Hakamada ◽  
Y. Chen ◽  
Hiromu Kusuda ◽  
Mamoru Mabuchi
Keyword(s):  
Absorption Coefficient ◽  
Pore Size ◽  
Sound Absorption ◽  
Size Range ◽  
Absorption Capacity ◽  
The Other ◽  
Sound Absorption Coefficient ◽  
Specimen Thickness ◽  
Pore Sizes ◽  
Other Hand

Porous Al specimens with a pore size range from 212-300 to 610-700 μm, a porosity from 85 to 95% and a specimen thickness from 2 to 20 mm were produced by the spacer method, and their sound absorption capacity was investigated. For these specimens, sound absorption coefficient increased with increasing porosity. On the other hand, sound absorption coefficient varied inconsistently with the variation of pore sizes. The latter may be attributed to variation of aperture sizes of each specimen because the porous Al specimens with differerent pore sizes produced by the spacer method should have different aperture sizes. Sound absorption coefficient increased at the frequency below 2000 Hz with increasing specimen thickness.

Acoustical Behavior of Treated Wood Dust-Filler for Polymer Foam Composite

2013 ◽  
Vol 465-466 ◽  
pp. 1039-1043 ◽  
Author(s):  
Shafizah Sa'adon ◽  
Anika Zafiah Mohd Rus
Keyword(s):  
Particle Size ◽  
Absorption Coefficient ◽  
Pore Size ◽  
Sound Absorption ◽  
Treated Wood ◽  
Sound Absorption Coefficient ◽  
Dust Particles ◽  
Wood Dust ◽  
Polymer Foam ◽  
Foam Composite

Wood dust filler-polymer foam composite has been studied and proved to have ability to absorb sound. In this study, treated rubber and Meranti wood dust named as RA and MA respectively was use as the filler. This study was developed to compare the behavior of sound absorption based on treated filler and particle size of wood dust. By choosing the size of 355 and 710 μm, three different percentages has been selected which is 10%, 15% and 20% for both type of wood dust. These samples has been tested by using Impedance Tube test for sound absorption coefficient (α) measurement and Noise Reduction Coefficient measurement (NRC) and Scanning Electron Microscopy (SEM) to determine the diameter of pore for selected size and type of wood dust-polymer foam composite. The pore size and structure was influence the sound absorption behavior of each sample. 355 μm-polymer foam composite of every percentage loading shows the uniform pore structure as compared to 710 μm of particle size. NRC results shows that increasing pore size has decrease the NRC value. It is therefore, concluded that the sound absorption coefficient for eachsound absorbing material, with different sizes of wood dust particles, types of wood dust and the percentages of wood dust loading in polymer foam matrix effect the sound absorption behavior.

scholarly journals Delignification Effects on Indonesian Momala (Homalium foetidum) and Korean Red Toon (Toona sinensis) Hardwood Pore Structure and Sound Absorption Capabilities

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5215
Author(s):  
Eun-Suk Jang ◽  
Chun-Won Kang
Keyword(s):  
Pore Structure ◽  
Noise Reduction ◽  
Pore Size ◽  
Sound Absorption ◽  
Gas Permeability ◽  
Air Gap ◽  
Toona Sinensis ◽  
Reduction Coefficient

Among the various methods used to improve the sound absorption capability of wood, we focused on delignification in Indonesian momala (Homalium foetidum) and Korean red toon (Toona sinensis). We performed gas permeability, pore size, and porosity analyses and evaluated how the change in the pore structure affects the sound absorption capabilities. Results show that delignification increased the through-pore porosity and improved sound absorption capability in both species. In addition, the air gap in the rear space maximized the sound absorption of momala and the red toon. The noise reduction coefficient (NRC) of delignified momala (90 min) with a 3 cm air gap was 0.359 ± 0.023. This is approximately 154.6% higher than that of untreated momala without an air gap. The NRC of delignificated red toon (90 min) with a 3 cm air gap was 0.324 ± 0.040, an increase of 604.3% over untreated red toon without an air gap.

scholarly journals Sound absorption characteristics of three species (binuang, balsa and paulownia) of low density hardwood

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Eun-Suk Jang ◽  
Chun-Won Kang
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Gas Permeability ◽  
Sound Absorption Coefficient ◽  
Low Density ◽  
High Porosity ◽  
Sound Waves ◽  
Low Frequencies ◽  
Absorption Performance ◽  
Closed Pore

Abstract In this study, the sound absorption coefficient of three low density hardwoods – binuang, balsa and paulownia – were investigated. Their gas permeability and pore size were measured, and their pore shapes were classified into through pore, blind pored, and closed pore, as specified by the International Union of Pure and Applied Chemistry (IUPAC). Among the three species, obvious that paulownia had lowest sound absorption when the two of others showed higher sound absorption. Although paulownia is a high porosity wood, most of its vessels are blocked by tyloses; it is therefore difficult for sound waves to enter its pores, which results in poor sound absorption performance. This study showed that the higher the through pore porosity, the higher was the gas permeability, which led to improvement of the sound absorption performance. It was also found that the sound absorption coefficient of the three species woods increased at low frequencies as the size of an air cavity between the specimens and tube’s wall increased.

Sound absorption of weft knitted fabrics: influence of fibers cross-section shape, stitch density and mechanical modification of surface

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mohammad-Reza Saffari ◽  
Mehdi Kamali Dolatabadi ◽  
Abosaeed Rashidi ◽  
Mohammad Esmail Yazdanshenas
Keyword(s):  
Absorption Coefficient ◽  
Cross Section ◽  
Cross Sections ◽  
Sound Absorption ◽  
Structural Parameters ◽  
Sound Absorption Coefficient ◽  
Sound Insulation ◽  
Knitted Fabrics ◽  
Content Type ◽  
Fiber Cross Section

PurposeOne of the recent applications of fabrics is to use them for sound insulation. Accordingly, due to their low production cost and low relative density, fabrics have drawn attention in some of the industries such as the automotive and aircraft industries. The present study is aimed to investigate the effects of the fiber cross-section, porosity, thickness of samples and fuzzing of the knitted fabric on the sound absorption coefficient.Design/methodology/approachIn the present study, fabrics with three different stitch densities were knitted by yarns consist of three different forms of fiber cross-section shapes (circular, elliptical and plus-shaped). In this work, the sound absorption coefficient of knitted fabrics was investigated with regard to the different fiber cross-sections and structural parameters using an impedance tube.FindingsAs indicated by the obtained results, the cross-section, porosity, thickness and mass per unit area of the fabrics were the determinant factors for the sound absorption coefficient. In addition to, the sound absorption coefficient and porosity were shown to have an inverse relationship.Originality/valueA section of the present paper has been allocated to the investigation of the effect of the fiber cross-section and fuzzing of fabric on the sound absorption of plain knitted fabrics.

Effect of heat treatment temperature and time on sound absorption coefficient of Larix kaempferi wood

2017 ◽  
Vol 63 (6) ◽  
pp. 575-579 ◽  
Author(s):  
Hyunwoo Chung ◽  
Yonggun Park ◽  
Sang-Yun Yang ◽  
Hyunbin Kim ◽  
Yeonjung Han ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Absorption Coefficient ◽  
Heat Treatment Temperature ◽  
Sound Absorption ◽  
Treatment Temperature ◽  
Sound Absorption Coefficient ◽  
Larix Kaempferi

Effect of characterization of porous metal fiber media on sound absorption coefficient

2015 ◽  
Vol 29 (10n11) ◽  
pp. 1540002 ◽  
Author(s):  
J. Z. Wang ◽  
Q. B. Ao ◽  
H. P. Tang ◽  
T. F. Bao
Keyword(s):  
Absorption Coefficient ◽  
Pore Size ◽  
Sound Absorption ◽  
Fiber Diameter ◽  
Average Pore Size ◽  
Porous Metal ◽  
International Standards ◽  
Sound Absorption Coefficient ◽  
Metal Fiber ◽  
Average Pore

Porous metal fiber media (PMFM) is a kind of advanced structural and functional material, and it has attracted a wide spread attention owing to excellent sound absorption performance. The sound absorption property of PMFM is mainly influenced by the fiber diameter, the average pore size and thickness of PMFM. In the paper, three stainless steel fibers with the diameters (∅) of 8, 12 and 20 μm were used to make PMFM with the average pore sizes of 10, 20, 30 and 40 μm and the thicknesses of 1, 2 and 3 mm by air-laid and sintering processes. The sound absorption coefficients of PMFM were tested in impedance tube using two-microphone transfer-function method according to ISO 10534-2 and ASTM E1050-98 international standards at room temperature. The results show that when the frequency ranges from 50 Hz to 6,400 Hz in material with the average pore size of 20 μm and the thickness of 3 mm and the fiber diameter of ∅8 μm, the average sound absorption coefficient is the highest.

scholarly journals Acoustic Panels Made of Paper Sludge and Clay Composites

2021 ◽  
Vol 13 (2) ◽  
pp. 637
Author(s):  
Tomas Astrauskas ◽  
Tomas Januševičius ◽  
Raimondas Grubliauskas
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Composite Panel ◽  
Sound Absorption Coefficient ◽  
Core Material ◽  
Paper Sludge ◽  
Frequency Range ◽  
Absorption Properties ◽  
Air Gaps ◽  
The Core

Studies on recycled materials emerged during recent years. This paper investigates samples’ sound absorption properties for panels fabricated of a mixture of paper sludge (PS) and clay mixture. PS was the core material. The sound absorption was measured. We also consider the influence of an air gap between panels and rigid backing. Different air gaps (50, 100, 150, 200 mm) simulate existing acoustic panel systems. Finally, the PS and clay composite panel sound absorption coefficients are compared to those for a typical commercial absorptive ceiling panel. The average sound absorption coefficient of PS-clay composite panels (αavg. in the frequency range from 250 to 1600 Hz) was up to 0.55. The resulting average sound absorption coefficient of panels made of recycled (but unfinished) materials is even somewhat higher than for the finished commercial (finished) acoustic panel (αavg. = 0.51).

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