Papers by Keyword: Sound Absorption

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Authors: Jia Horng Lin, Chia Chang Lin, Jin Mao Chen, Yu Chun Chuang, Ying Hsuan Hsu, Ching Wen Lou
Abstract: Noise pollution has become a kind of serious environmental pollution problems. It not only makes people feel fatigue but also affects their concentration and work efficiency. People’s health and work efficiency could be promoted by improving and reducing the noise pollution problem. In this research, the recycled polyester (PET) fibers, polypropylene (PP) fiber and flame-retardant-hollow-crimp 7D PET fiber with a ratio of 2:1:7, 2:2:6, 2:3:5, 2:4:4, and 2:5:3 were fabricated and then needle-punched, creating the PET/PP/PET fabric. Next, a layer of recycled PP selvage and a layer of fabric were laminated in turn on the base fabric before needle-punching with a certain punching-depth, which was repeated until the 10-layer PET/PP/PET nonwoven composite was completed. Finally, the resulting PET/PP/PET nonwoven composite was measured with its physical properties and sound absorption ability.
Authors: Jia Horng Lin, Chen Hung Huang, Kuo Cheng Tai, Chia Chang Lin, Yu Chun Chuang, Ching Wen Lou
Abstract: The rapid advances in technology have driven people for seeking ways to improve the quality of their living environment. While excessive noise is more likely to affect people physically and psychologically such as tiredness, dulling of the senses, lack of concentration, and reduction in work efficiency, etc, therefore, noise suppression has become an important research issue. In this research, 7 D polyester staple fiber and 4 D low melting point fiber have been used to fabricate the polyethylene terephthalate (PET) fabric through the process of opening, blending, carding lining, lapping, and needle-punching. Meanwhile, the contents of low-melting point polyester fiber are varied as 10 wt%, 20 wt%, 30 wt%, 40 wt% and 50 wt% in PET fabric. The physical properties of PET fabrics are then evaluated after hot pressing process. Experimental results show that 50 wt% low-melting point polyester fiber is the best choice for PET fabric. Further, the techniques of lamination and multiple needle-punching are employed to make the PET/PP composite sound-absorbing board. A layer of polypropylene (PP) nonwoven selvages is placed between two layers of PET fabrics in the process of lamination. The PET/PP fibers casted into a mold are then put into a hot-air circulation oven around 170 °C for 10 minutes. Afterwards, the evaluation of PET/PP composite sound-absorbing board on sound absorption, flame resistance, thermal insulation, and relative mechanical properties is properly conducted.
Authors: Jia Horng Lin, Chen Hung Huang, Kuo Cheng Tai, Chia Chang Lin, Yi Ting Tsai, Ching Wen Lou
Abstract: This research is to develop a processing technique for fabricating the three-dimensional nonwoven fabric with the sound absorption capability and flame retardant capability. Furthermore, the physical properties and functionalities of the three-dimensional nonwoven fabric are adequately evaluated and tested. Several nonwoven fabrics are fabricated by two polyester fibers with different denier numbers and the low-melting-point fibers. Then, multiple nonwoven fabrics are used to make three-dimensional nonwoven fabrics through lapping, needle-punching process. After being reinforced by heating in the hot air circulation oven, the physical properties of three-dimensional nonwoven fabrics such as tensile strength, breathability, sound-absorption coefficients, limiting oxygen index (LOI), and thermal conductive coefficients are properly evaluated. Subsequently, the influence of fiber faintness on the performance of sound-absorption and thermal insulation of three-dimensional nonwoven fabrics is carefully examined through the obtained results.
Authors: Jia Horng Lin, Chen Hung Huang, Ying Huei Shih, Yu Chun Chuang, Ching Wen Lin, Ching Wen Lou
Abstract: The rapid development of textile industry at the beginning of the Industrial Revolution results in the invention of synthetic fibers. As synthetic fibers cannot be decomposed naturally, significant textile waste is thus created. Selvages, which make up the majority of our total garbage output, have a low value and thus are usually sold cheaply or outsourced as textile waste. This study aims to recycle and reclaim the nonwoven selvages which are discarded by the textile industry. The recycled polypropylene (PP) selvages, serving as a packing material, and 6 denier PP staple fibers are made into the recycled PP nonwoven fabrics. The resulting nonwoven fabrics are subsequently tested in terms of maximum tensile breaking strength, tearing strength, surface observation, thickness measurement and sound absorption coefficient.
Authors: Bin Zhang, Xiao Ling Gai, Xian Hui Li
Abstract: Microperforated panel (MPP) absorbers have been developed rapidly and used in many fields in recent years. First, based on the Maa’s theory, the theoretical development of MPP is reviewed in this paper. Furthermore, structure design and processing technology of MPP are introduced. Finally, the further development of MPP is discussed.
Authors: Yan Xiang Li, W.W. Yuan, X. Chen
Abstract: Metallic foams of A356 alloy with a uniform porosity of 75-85% were produced with the melt foaming process. The microstructure inside the foam cell walls was experimentally studied. It is found that the microstructure is greatly different from the as-cast structure of the base alloy. It is believed that the thickening process with calcium, the adding of foaming agent and the mixing process during the production process all play important roles on the solidification microstructure of the cell walls. The morphology and grain size of primary α-phase, the amount and morphology of eutectic silicon, the distribution and size of CaSi2Al2 and residual titanium hydride particles were studied. The sound absorption coefficient of the alloy foams was measured. Two methods, drilling small holes and compressing the foam, have been developed to improve the sound absorbability of the alloy foam in low and middle frequency ranges.
Authors: Tetsumune Kuromura, Masataka Hakamada, Y. Chen, Hiromu Kusuda, Mamoru Mabuchi
Abstract: 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.
Authors: Garoum Mohammed, Chaimaa Benayad
Abstract: Knowledge of acoustical properties of granular and fibrous sustainable materials has been stimulated thanks to their rather easy handling and durability. In this work direct measurements of the normal incidence sound absorption coefficient of three non consolidated materials (esparto fibers, cork and perlite) have been carried out using the so-called transfer function method. These materials are plentiful in Morocco and they require low amounts of energy for processing, which makes them attractive as either thermal insulating or sound absorbing materials. Results show that the acoustical efficiency of studied materials is comparable to traditional materials. In addition, an inverse estimation of non acoustical parameters (flow resistivity, tortuosity and porosity) of these materials has been performed introducing a new predictability approach. This is based on Global Sensitivity Analysis combined with Global Numerical Optimization Techniques, regarding most usual mathematical models.
Authors: Noor Quratul Aine Adnan, Anika Zafiah M. Rus
Abstract: Biopolymer foam was prepared based on vegetable oil and Polyol Flexible (Epoxy) with commercial Polymethane Polyphenyl Isocyanate (Modified Polymeric-MDI) as laminated foam. The acoustic property of biopolymer foam was examined by impedance tube test according to ASTM E-1050 of sound absorption coefficient (α). From the result obtain, sample D and sample C are the best result of sound absorption coefficient (α) for biopolymer foam and epoxy foam with the value are 0.867 and 0.817 respectively. By using the sound behavior theory, when the thickness is increase the sound absorption is also increase as same as in this study. The noise reduction coefficient (NRC) of sample D is 38.26% while for sample C is 37.42%.
Authors: Sang Youl Kim, Soo Han Park, Yong Su Um, Bo Young Hur
Abstract: Aluminum foam with 0.2 g/cm3 density showed a good sound absorption property at frequencies higher than 2000 Hz. Compressed aluminum foam with an air gap of 50 mm or higher exhibited a very high sound absorption property near 400 Hz.
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