• The Journal of the Acoustical Society of Korea
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• v.40 no.6
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• pp.649-659
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• 2021

Wall absorption treatment effectively reduces reverberation, but requires a large area for a live room and each wall absorption affects speech intelligibility differently. In this study, we try to find the most effective wall for the absorption treatment using the beamforming array microphone in terms of speech intelligibility. The absorption importance factor is defined by using the collision number of reflected sounds on each wall. It allows estimating how much the speech signal will be enhanced by the absorption treatment. A cuboid room with a size of 107 m³ and a reverberation time of 1.1 s is selected for the simulation. When a Helmholtz-type absorption is treated on the wall with the most significant importance factor, the modified clarity for 500 and 1k Hz is improved by 5.1 dB and 4.8 dB respectively, and the speech transmission index is enhanced by 0.06. The difference in results between the proposed method and commercial simulation code is less than a Just-Noticeable Difference (JND). The absorption treatment on the wall with the most significant importance factor shows improvement greater than the wall with the largest area, and its difference is larger than a JND value.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.2
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• pp.163-170
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• 2022

The present study investigates NO_x-removal and sound-absorption performances of photocatalytic porous concrete prepared by various TiO₂ application methods. Photocatalytic porous concrete samples were prepared by one of the following: 1) mechanically mixing TiO₂ during casting; 2) mixing bottom ash aggregate pretreated with TiO₂ during casting; and 3) spraying TiO₂ solution to the normally fabricated porous concrete. The test results indicated that the mechanical mixing of TiO₂ decreased the compressive strength as the added TiO₂ content increased. The use of pretreated bottom ash aggregate reduced the porosity, yet the compressive strength of the concrete was similar to that measured from the former method. Porous concrete samples sprayed with the TiO₂ solution exhibited enhanced compressive strength, while the porosity was analogous to those measured from other methods. The NO_x-removal performance was the highest in the samples sprayed with the TiO₂ solution, followed by the samples using pretreated bottom ash aggregate and mechanically mixed TiO₂. The samples with mechanically mixed TiO₂ identified a relationship between soundabsorption performance and porosity. However, no particular tendency was observable in the samples with other TiO₂ application methods.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.481-487
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• 2017

The purpose of this study is to develop the hybrid sound-absorbing materials that is made from organic polyurethane sponge impregnated with inorganic binder solutions. The inorganic slurry which is made from ${\alpha}$-hemihydrate gypsum mixed with 60% water, and various additives including plasticizer are used as binder. The test specimens are prepared and tested for sound absorption performance by the impedance tube methods. From the test results, noise reduction coefficient(NRC) of development materials specimen bound by the inorganic binder slurry is 0.41. They are 2 times or more higher than commercial products specimens bound by organic materials only which have NRC values in the range of 0.14 to 0.28. The polyurethane sponge specimens impregnated with inorganic gypsum slurry binder have a good balance between performance and cost, and have proper properties in density, thermal conductivity, non-combustible, and absence of harmful substances as sound-absorbing internal boards for noise barrier wall. It is apparent that the good sound absorption materials can be produced according to the optimum mix design that is recommended from this study.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.594-601
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• 2021

In order to expanding of the use of steel slag, a by-product of steel industry, as a road paving construction material, this present study confirmed the possibility of the rust formation of steel slag aggregate and evaluated the durability performance and the noise reduction characteristics of asphalt concrete mixture. As a result of conducting the rust formation test of aggregate, no rust was observed in both aggregate, so it is judged that the possibility of rust formation in the actual road water environment is very low. As a result of performing the moisture resistance test, all mixtures showed a tensile strength ratio exceeding 85%, satisfied the standard as asphalt mixture. In addition, the sound absorption coefficient of the steel slag aggregate mixture was measured to be higher than that of the general aggregate mixture. Accordingly, it is speculated th at th e steel slag aggregate mixture can more effectively respond to road noise reduction than the general mixture.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.501-508
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• 2023

Addressing urban noise problems, this study develops eco-friendly, inorganic sound-absorbing panels, overcoming the limitations of traditional PMMA and cement-based panels. These conventional panels pose safety risks due to flammability and environmental concerns due to carbon emissions. Utilizing industrial waste, the research comprises two phases: initial tests for physical and performance characteristics (fluidity, density, compressive strength, sound absorption) and subsequent development of optimized panel mixtures. This approach aims to replace existing panels with sustainable, effective alternatives, significantly contributing to safer, environmentally responsible urban infrastructure. The findings of this study have implications for the sound panel market, offering novel solutions for noise control while aligning with environmental and safety standards.

• International Journal of Highway Engineering
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• v.7 no.3 s.25
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• pp.31-42
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• 2005

This study evaluates the physical mechanical properties, durability and sound absorbtion of porous concrete for pavement according to content of silica fume and steel fiber to elicit the presentation of data and the way to enhance its function for the practical field application of porous concrete as a material of pavement. The results of the test indicate that in every condition, the void ratio and the coefficient of water permeability of porous concrete for pavement satisfy both the domestic standards and proposition values. Among the properties of strength, the compressive strength satisfies the standards in the specification of Korea National Housing Corporation as for every factor of mixture but in the case of the flexural strength, more than 0.6vol.% of steel fiber satisfied the Japan Concrete Institute proposition values. The mixture of silica fume and steel fiber presents the excellent intensity, though. The case when silica fume and steel fiber are used simultaneously presents the strongest durability because the durability shows the similar tendency to the dynamic characteristics. The case when 10wt.% of silica fume and 0.6vol.% of steel fiber are used at the same time shows that the loss rate of mass by Cantabro test became 27% better and freeze-thaw resistance became 60% better. As for the characteristics of sound absorption of porous concrete for pavement, Noise Reduction Coefficient is 0.48 to prove that it possesses almost 50% sound absorption.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.617-618
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• 2009

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.270-275
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• 2009

Sound absorption characteristics of membrane system which are used in stadiums and arenas were investigated. Theoretical studies on acoustic properties of single and double leaf permeable membrane conducted. Also, experimental studies on sound absorption characteristics of combined membrane system that is composed of outer and inner membrane material were conducted. In this study, sound absorption characteristics of each membrane were investigated by experiments in reverberation chamber. 4 types of permeable membranes and a non-permeable membrane were used for experiments. Air space behind membrane material and tension on the membrane was varied. Sound absorption performance of permeable membrane materials was confirmed. As increasing air space behind the membrane material, sound absorption coefficient was increased. In a resonance absorption frequency band sound absorption coefficient varied more dramatically. Sound absorption characteristics were flat in mid and high frequency range and sound absorption coefficient was from 0,3 to 0,5. Also sound absorption coefficient was increased by the increment of surface density and air permeability of membrane. However, over the certain value of air permeability, sound absorption coefficient was decreased. These results can be used as design factors and method for the room acoustic design of dome-stadiums and large free-form buildings.

• The Research Journal of the Costume Culture
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• v.20 no.4
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• pp.475-484
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• 2012

The purpose of this study is to help to prevent daily noises by measuring the noise absorption coefficient of the non-woven fabrics and wallpapers which are commonly used in lining and noise absorption coefficient of lining curtain. Seven types of fiber materials for the interior decoration, one non-woven fabric for the wallpaper linings, and two types of textiles for curtain linings are used as the experimental materials in this study. The noise absorption coefficient of the noise absorbents were measured by using impedance tube. And the thermal transmittance were measured by using thermal transmittance tester. The results of this study are as follows; Observing the noise absorption efficiency of each experimental materials, the combination of fiber materials and linings, the noise absorption efficiency of cotton, polyester and silk were similar and for the experimental materials of flax, rayon, acrylic and nylon were resulted the similar noise absorption efficiency. The result of combination of fiber material and black fabric was highest among the combined linings. For the combination of fiber material and non-woven fabric, double layers of non-woven fabric resulted slightly higher noise absorption coefficient result than single layer of non-woven fabric. The thermal transmittance and the sound absorbents of experimental materials were affected by the thickness, density and layer of air of the experimental materials.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.4
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• pp.365-371
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• 2013

The purpose of this study is to develop a sound absorbing material for indoor which manufactured by a clay and binding material. The seven kind of sound absorbing specimens which sintered through a mold process at high temperature were manufactured for the purpose of testing sound absorption performance. The random and normal sound absorption coefficients were measured for the sintered clay sound absorbing specimens with different particle size, density and mixture ratio. From the experimental results, it was found that its particle size was closely related to the sound absorption performance. It was shown that the sintered clay sound absorbing specimen had the sound absorption properties of a fiber-type or a resonance-type sound absorbing material depending on the particle size.