scholarly journals How do the Pore Traits of Hardwoods Affect Sound Absorption Performance of their Cross Sections? - Focusing on 6 Species of Korean Hardwoods

2021 ◽  
Author(s):  
Eun-Suk JANG ◽  
Chun-Won KANG
Keyword(s):  
Pore Structure ◽  
Thermal Insulation ◽  
Cross Sections ◽  
Sound Absorption ◽  
Gas Permeability ◽  
High Frequencies ◽  
Absorption Performance ◽  
The Cross ◽  
Closed Pore ◽  
Diffuse Porous

Abstract An investigation of sound absorption in 6 species of hardwoods according to the pore structure of cross-sections revealed that higher gas permeability was associated with greater sound absorption at high frequencies. In addition, diffuse-porous wood exhibited superior sound absorption performance compared with ring-porous wood. Through-pore porosity was associated with improved sound absorption in the cross-sections of all 6 species, while closed-pore porosity was associated with poor sound absorption. The results of these studies could lead to development of hardwood products with superior sound absorption and help elucidate the roles of porosity in drying, impregnation, and thermal insulation properties of wood.

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.

scholarly journals Sound absorption characteristics of KGM-based aerogel

2020 ◽  
Vol 15 (3) ◽  
pp. 450-457
Author(s):  
Yixin Wang ◽  
Fei Xiang ◽  
Wei Wang ◽  
Weiling Wang ◽  
Yuehong Su ◽  
...  
Keyword(s):  
Pore Structure ◽  
Sound Absorption ◽  
Freeze Drying ◽  
Drying Method ◽  
Absorption Potential ◽  
Absorption Performance ◽  
Property Characterization ◽  
High Sound ◽  
Absorption Characteristics

Abstract This study presents the preparation and property characterization of biomass aerogels as sound absorption materials. Biomasses were chosen to prepare aerogels through the freeze-drying method. Results indicated that four components may have different effects on the aerogel pore structure, and the aerogel formula was thus optimized to reach the best sound absorption. Within the experimental range, biomass aerogel with the optimized formula had an average sound efficiency 0.352, density 0.047 g/cm3 and porosity 94.46 ± 0.04%. It shows better sound absorption performance than traditional sound absorption cotton. These results demonstrate the high sound absorption potential of biomass aerogels for building applications.

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.

A Compact Hybrid Sound Absorber Using Flexible Micro-Perforated Panel and Piezoelectric Actuator

2013 ◽  
Vol 325-326 ◽  
pp. 8-11
Author(s):  
Wei Guang Zheng ◽  
Ying Feng Lei ◽  
Qi Bai Huang ◽  
Chuan Bing Li
Keyword(s):  
Hybrid System ◽  
Piezoelectric Actuator ◽  
Sound Absorption ◽  
Low Frequency ◽  
Combined Approach ◽  
High Frequencies ◽  
Sound Absorber ◽  
Vibration Effect ◽  
Piezoelectric Patch ◽  
Absorption Performance

This paper presents the concept of a compact hybrid sound absorber, based on a combined approach for sound absorption. A flexible micro-perforated panel (MPP) is used as the passive sound absorber for mid and high frequencies and a piezoelectric patch as the active control actuator for low frequency. The volume of this new absorber is highly reduced compare to conventional hybrid systems which employ porous layer as passive part and loudspeaker as active part. The vibration effect of the MPP in the hybrid system is also considered. Theoretical and experimental results show that the flexible MPP has the potential to dissipate more energy and can be utilized to improve absorption performance of the hybrid system by appropriately selecting its parameters.

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.

Improving the sound absorption performance of sustainable thermal insulation materials: Natural hemp fibres

2019 ◽  
Vol 150 ◽  
pp. 279-289 ◽  
Author(s):  
Andrea Santoni ◽  
Paolo Bonfiglio ◽  
Patrizio Fausti ◽  
Cristina Marescotti ◽  
Valentina Mazzanti ◽  
...  
Keyword(s):  
Thermal Insulation ◽  
Sound Absorption ◽  
Insulation Materials ◽  
Hemp Fibres ◽  
Absorption Performance

Effect of fiber cross-section on the transport and acoustic properties of fibrous materials

2021 ◽  
Vol 263 (5) ◽  
pp. 1239-1242
Author(s):  
Sung Soo Yang ◽  
Yeon June Kang
Keyword(s):  
Cross Sections ◽  
Sound Absorption ◽  
Characteristic Length ◽  
Thermal Characteristic ◽  
Acoustic Energy ◽  
Acoustic Properties ◽  
Fibrous Materials ◽  
Cell Structures ◽  
Rigid Frame ◽  
Absorption Performance

Fibrous materials can efficiently dissipate acoustic energy, and their intrinsic properties are determined by fiber geometries (microscale). In this study, the effect of cross-sections of fibers on the transport and acoustic properties of fibrous materials was investigated. First, fibers of various cross-sections were modeled by adjusting their open porosity. The representative elementary volumes of fiber structures were generated to describe the periodic unit-cell structures. Next, the transport properties (such as static airflow resistivity, high-frequency limit of the dynamic tortuosity, viscous characteristic length, thermal characteristic length, and static thermal permeability) of fibrous materials were calculated by solving numerical problems using the finite element method. These properties of fibrous materials with complex cross-sections were compared with those with circular cross-sections. Finally, the sound absorption coefficients were predicted using the Johnson-Champoux-Allard-Lafarge (JCAL) model and rigid frame approximation, and the differences in sound-absorbing behavior were analyzed. This study can provide insights into the design of lightweight fibrous materials while maintaining optimal sound absorption performance.

The cross sections for different channels in heavy ion nuclear reactions

1971 ◽  
Vol 32 (1) ◽  
pp. 7-9 ◽  
Author(s):  
J. Galin ◽  
D. Guerreau ◽  
M. Lefort ◽  
X. Tarrago
Keyword(s):  
Cross Sections ◽  
Nuclear Reactions ◽  
Heavy Ion ◽  
The Cross

Experimental Studies Of Multilayer Glass Structures On Compression, Compression With Bending And Simple Bending

2019 ◽  
pp. 22-30
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Applied Load ◽  
Experimental Studies ◽  
Strength Properties ◽  
Research Topic ◽  
Normative Values ◽  
Laminated Glass ◽  
The Cross ◽  
Experimental Values

The work of multilayer glass structures for central and eccentric compression and bending are considered. The substantiation of the chosen research topic is made. The description and features of laminated glass for the structures investigated, their characteristics are presented. The analysis of the results obtained when testing for compression, compression with bending, simple bending of models of columns, beams, samples of laminated glass was made. Overview of the types and nature of destruction of the models are presented, diagrams of material operation are constructed, average values of the resistance of the cross-sections of samples are obtained, the table of destructive loads is generated. The need for development of a set of rules and guidelines for the design of glass structures, including laminated glass, for bearing elements, as well as standards for testing, rules for assessing the strength, stiffness, crack resistance and methods for determining the strength of control samples is emphasized. It is established that the strength properties of glass depend on the type of applied load and vary widely, and significantly lower than the corresponding normative values of the strength of heat-strengthened glass. The effect of the connecting polymeric material and manufacturing technology of laminated glass on the strength of the structure is also shown. The experimental values of the elastic modulus are different in different directions of the cross section and in the direction perpendicular to the glass layers are two times less than along the glass layers.

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