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 Dispersion of Acoustic Energy in the Dissemination from the Source

2014 ◽  
Vol 899 ◽  
pp. 513-516
Author(s):  
Dušan Dlhý ◽  
Alena Pernišová
Keyword(s):  
Cross Section ◽  
Sound Absorption ◽  
Sound Propagation ◽  
Acoustic Energy ◽  
Acoustic Properties ◽  
Technological Equipment ◽  
Source Position ◽  
Energy Propagation ◽  
Sound Sources ◽  
Sound Levels

Methodology of the way of supposed sound levels calculations in closed objects areas from the sound sources is based on assumptions, that the propagation of sound is dominant. In many cases the acoustic properties of space of sound propagation have great importance. We have to take in the consideration - the size and cross-section areas of dispersion bodies, their sound absorption coefficient; - shape of area and boundary areas absorption; - position of concerning point in relation to the source position in space; - noise of technological equipment and relatively other coefficients that may effect the sound energy propagation.

scholarly journals Acoustic Properties of Sound Absorber from Modified Polyester with Filler Sodium Bicarbonate

2018 ◽  
Vol 34 (4) ◽  
pp. 2187-2191
Author(s):  
Nasmi Herlina Sari ◽  
Jauhar Fajrin
Keyword(s):  
Absorption Coefficient ◽  
Sodium Bicarbonate ◽  
Acoustic Impedance ◽  
Sound Absorption ◽  
Polyester Resin ◽  
Acoustic Properties ◽  
Acoustic Parameters ◽  
Absorbent Material ◽  
Sound Absorber ◽  
Absorption Performance

The combination of low price, ease of manufacturing and waterproofing characteristics has placed polyester resin as a potential sound absorbent material. Previous studies showed that adding filler material to the blending may increase the acoustics properties of a sound absorbent material. This study aims to investigate the potential of sodium bicarbonate (NaHCO3) to be employed as a filler to improve the acoustic properties of the sound absorber made of polyester resin. Two important acoustic parameters were carefully assessed; absorption coefficient and acoustic impedance. The results showed that the sound absorption performance increased significantly at low and medium frequencies in the presence of NaHCO3 filler in polyester resin. Meanwhile, the use of a back cavity on the absorbent material reduced the sound absorption performance of materials at low and medium frequencies. This suggests that sound absorber made of polyester with sodium bicarbonate filler may be used as an alternative for sound absorber materials.

scholarly journals A Pilot Study on the Sound Absorption Characteristics of Chicken Feathers as an Alternative Sustainable Acoustical Material

2019 ◽  
Vol 11 (5) ◽  
pp. 1476 ◽  
Author(s):  
Asniawaty Kusno ◽  
Kimihiro Sakagami ◽  
Takeshi Okuzono ◽  
Masahiro Toyoda ◽  
Toru Otsuru ◽  
...  
Keyword(s):  
Pilot Study ◽  
Sound Absorption ◽  
Prediction Method ◽  
Fibrous Materials ◽  
Absorption Coefficients ◽  
Chicken Feathers ◽  
Absorption Performance ◽  
Flow Resistivity ◽  
Impedance Tube Method ◽  
Absorption Characteristics

This communication reports the results of a pilot study on the sound absorption characteristics of chicken feathers (CFs). Recently, demands for natural and sustainable materials have been extensively studied for acoustical purposes. CF has long been left wasted, however, they can be used for sound-absorbing purposes to improve acoustical environments as a sustainable and green acoustical material. In order to clarify their feasibility, samples of CF absorbers of various densities and thicknesses were prepared, and their sound absorption coefficients were measured by the standard impedance tube method. The measured results were also compared with those of conventional glass wools of the same densities and thicknesses. The results show that CFs have potentially good sound-absorption performance, which is similar to typical fibrous materials: increasing with frequency. Results of direct comparison with glass wool demonstrate that the absorption coefficients of CFs are comparable and, at some frequencies, somewhat higher than conventional glass wools in some cases. Additionally, the first step for searching a prediction method for the sound absorption performance of CFs, their flow resistivity was measured and a Delany–Bazley–Miki model was examined. However, the resultant flow resistivity was unexpectedly low, and the model gave only a much lower value than that measured. The reason for the discrepancies is the subject of a future study.

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.

Method of Determining the Sound Absorbing Coefficient of Materials within the Frequency Range of 5 000–50 000 Hz in a Test Chamber of a Volume of about 2 m3

2013 ◽  
Vol 38 (2) ◽  
pp. 177-183 ◽  
Author(s):  
Witold Mikulski
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Harmful Effect ◽  
Test Chamber ◽  
Acoustic Energy ◽  
Acoustic Properties ◽  
Sound Absorption Coefficient ◽  
Frequency Range ◽  
Absorbing Materials ◽  
Method Of Measurement

Abstract Sound absorption coefficient is a commonly used parameter to characterize the acoustic properties of sound absorbing materials. It is defined within the frequency range of 100-5 000 Hz. In the industrial conditions, many appliances radiating acoustic energy of the frequency range of above 5000 Hz are used and at the same time it is known that a noise within the frequency range of 5 000-50 000 Hz can have a harmful effect on people,hence there is a need to define the coefficient in this frequency range. The article presents a proposal for a method of measurement of the sound absorption coefficient of materials in the frequency range from 5 000 Hz to 50 000 Hz. This method is a modification of the reverberation method with the use of interrupted noise.

scholarly journals Sound Absorption Measurements of Bio-Sourced Esparto-Fibres : Effect of the Compression

2020 ◽  
Vol 9 (2) ◽  
pp. 1827-1832
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Normal Incidence ◽  
Density Variation ◽  
Thickness Variation ◽  
Fibrous Materials ◽  
Low Frequencies ◽  
Conference Room ◽  
Innovative Solution ◽  
Absorption Performance

The use of absorbent materials such as fibrous materials is considered as an innovative solution to solve noise problems. The purpose of this research paper is to study the acoustic absorption of a new bio-sourced fibrous material called "Alfa fibers", in order to use it as an absorbent material to reduce reverberation time in the building construction domain (theatre, cinema, conference room, ...). For that, a set of 36 samples was designed and prepared for different thicknesses and different densities in order to evaluate the effect of thickness variation and density variation on sound absorption performance. An experimental study was carried out to measure the sound absorption coefficient at normal incidence, using the ISO 10534-2 standard method known as two-microphone transfer function method. All tests were performed in a Kundt tube with a diameter of 10 cm, in the frequency range (50-1600 Hz). These measurements show that the absorption coefficient can reach a value of 0.9 around 1000 Hz. The experimental results clearly show that sound absorption improves when the thickness of the samples increases, or when the density increases to an optimal value of 300Kg/m3 from which absorption performance begins to decrease. At low frequencies, sound absorption can be improved by creating an air gap between the sample and the rigid bottom.

scholarly journals Investigation of Acoustic Properties on Wideband Sound-Absorber Composed of Hollow Perforated Spherical Structure with Extended Tubes and Porous Materials

2020 ◽  
Vol 10 (24) ◽  
pp. 8978
Author(s):  
Dengke Li ◽  
Zhongcheng Jiang ◽  
Lin Li ◽  
Xiaobo Liu ◽  
Xianfeng Wang ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Three Dimensional ◽  
Low Frequency ◽  
Acoustic Properties ◽  
Low Frequencies ◽  
Frequency Sound ◽  
Sound Absorber ◽  
Spherical Structure ◽  
Absorption Performance ◽  
Melamine Foam

Traditional porous media such as melamine foam absorb sound due to their three-dimensional porous struts. However, the acoustic properties at low frequencies are greatly related to its thickness. In this paper, a novel type of thin and lightweight sound absorber composed of melamine foam and hollow perforated spherical structure with extended tubes (HPSET) is introduced to enhance the sound absorption performance at low frequencies. A theoretical model for the normal absorption coefficient of the HPSET with melamine foam is established. Good agreements are observed between the simulated and the experimental results. Compared with the virgin melamine foam, the proposed absorber can greatly improve the low-frequency sound absorption and retain the mid- to high-frequency sound absorption, while the thickness of the proposed absorber is less than 1/28 of the wavelength.

scholarly journals Factors Affecting Acoustic Properties of Natural-Fiber-Based Materials and Composites: A Review

Textiles ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 55-85
Author(s):  
Tufail Hassan ◽  
Hafsa Jamshaid ◽  
Rajesh Mishra ◽  
Muhammad Qamar Khan ◽  
Michal Petru ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Fiber Type ◽  
Alkali Treatment ◽  
Acoustic Properties ◽  
Synthetic Fiber ◽  
Sound Insulation ◽  
Factors Affecting ◽  
Wide Range

Recently, very rapid growth has been observed in the innovations and use of natural-fiber-based materials and composites for acoustic applications due to their environmentally friendly nature, low cost, and good acoustic absorption capability. However, there are still challenges for researchers to improve the mechanical and acoustic properties of natural fiber composites. In contrast, synthetic fiber-based composites have good mechanical properties and can be used in a wide range of structural and automotive applications. This review aims to provide a short overview of the different factors that affect the acoustic properties of natural-fiber-based materials and composites. The various factors that influence acoustic performance are fiber type, fineness, length, orientation, density, volume fraction in the composite, thickness, level of compression, and design. The details of various factors affecting the acoustic behavior of the fiber-based composites are described. Natural-fiber-based composites exhibit relatively good sound absorption capability due to their porous structure. Surface modification by alkali treatment can enhance the sound absorption performance. These materials can be used in buildings and interiors for efficient sound insulation.

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.

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