• Title/Summary/Keyword: Sound-Absorbing material

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Measurement of Reflection Coefficient of Sound Absorbent Material with Respect to Angle of Incidence and Its Associated Errors (입사각에 따른 흡음재의 반사 계수 측정 방법론 및 오차에 대한 고찰)

  • 이수열;김상렬;김양한
    • Journal of KSNVE
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    • v.4 no.3
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    • pp.295-305
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    • 1994
  • The reflection coefficient of a material at oblique incidence is measured in a free field. The sound pressure distributions are measured at discrete points on two measurement lines and then decomposed into plane wave components by using spatial Fourier transform. The inciedent and reflected plane wave components are obtained from a set of "decomposition equations" of which uses the plane wave propagation theory. Numerical simulations and experiments have been performed to see the effect of finite size of measurement area. To reduce this effect, a window fuction has been performed to see the effects of finite size of mesurement area. To reduce this effect, a window function has been proposed and its effect on the measurement of sound absorbing material property has been studied as well. The reflection coefficient obtained by this method is compared with those obtained from other methods; 2-microphone method in a duct and an expirical equation of which determines the characteristic impedance .rho.c and propagation constant k of a material from flow resistance information.formation.

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A Study on Squeal Noise Control by Absorption Treatment in Urban Rail Transit System (흡음에 의한 도시철도 곡선부 스퀼 소음저감에 관한 연구)

  • 최진권;이재원;장서일
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.11 no.4
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    • pp.58-64
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    • 2001
  • Sound absorbing materials are applied to the exposed surfaces of curvet subway tunnel for the reduction of curving noise level. Before the treatment, acoustical engineering simulation is performed to predict the noise level reduction for different kinds and amounts of absorbing material. The principle of geometrical acoustics is utilized to perform the simulation efficiently and accurately. The noise bevels of the inside and outside of running car body are measured to find the noise level reduction. The average noise level reduction of 8 dB has been attained. It has been shown that the simulated results are comparable to the measured ones.

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Low frequency sound absorption improvement in refrigerator using multi perforated plate (다공판을 활용한 냉장고 저주파 흡음개선)

  • Ho-Jin, Kwon;Hyoung-Jin, Kim;Kyungjun, Song;Tae-hoon, Kim;Junhyo, Koo
    • The Journal of the Acoustical Society of Korea
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    • v.41 no.6
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    • pp.723-729
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    • 2022
  • In this study, the multi perforated plate is used to reduce the compressor noise in the low frequency band inside the refrigerator machine room. To predict the sound absorption results, the impedance of the sound absorption material is measured. Using the measured impedance results, it is confirmed that the results used for FEM analysis is almost similar to the experimental values. The sound-absorbing structure that can operate in the target frequency band inside the refrigerator machine room is designed by controlling the hole diameter and arrangement in the perforated plate. The effect of reducing noise in the low frequency band is confirmed by applying perforated plate-based sound absorbing structures to the machine room.

A Study on the Sound Absorption Properties of Cellular Concrete with Continuous voids (연속공극을 갖는 기포콘크리트의 흡음특성에 관한 연구)

  • Lee, Seung-Han;Jung, Yong-Wook;Park, Jung-Jun
    • Journal of the Korea Concrete Institute
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    • v.15 no.4
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    • pp.566-573
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    • 2003
  • This study was performed to manufacture a rigid sound absorbing material by increasing the continuous void ratio of cellular concrete, thereby achieving an increase in sound absorption ratio and an enhancement in strength of the cellular concrete. By the experiments, it was determined that an increase in sound absorption ratio is achieved by increasing the added amount of air voids, thereby increasing the continuous void ratio. When the material had a thickness of 5 cm, a satisfactory average sound absorption ratio of 70% was obtained at a continuous void ratio of 40% or more. An increase in the thickness of the sound absorbing material resulted in an increase in sound absorption ratio in a super bass range. The specific gravity of cellular concrete meeting an average sound absorption ratio of 70% was 0.4 at a material thickness of 5 cm, and 0.6 or less at a material thickness of 7 cm. The compressive strength of the cellular concrete having a specific gravity of 0.4 meeting an average sound absorption ratio of 70% or more was 1.37 Mpa at a cement fineness of 3,000. This compressive strength was increased to 3.34 MPa at a cement fineness of 8,000. Accordingly, it was determined that the compressive strength of cellular concrete having continuous voids increases with a higher cement fineness.

A Study on Curving noise control by absorption treatment in Urban Rail Transit System (흡음에 의한 도시철도 곡선부 소음저감에 관한 연구)

  • 이재원;손진희;장서일
    • Proceedings of the KSR Conference
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    • 2002.05a
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    • pp.603-608
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    • 2002
  • Sound absorbing materials are applied to the exposed surfaces of curved subway tunnel for the reduction of curving noise level. Before the treatment, acoustical engineering simulation is performed to predict the noise level reduction for different kinds and amounts of absorbing material. The principle of geometrical acoustics is utilized to Peform the simulation efficiently and accurately. The noise levels of the inside and outside of running car body are measured to find the noise level reduction. The average noise level reduction of 8 ㏈ has been attained. It has been shown that the simulated results are comparable to the measured ones.

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Study on the Sound Absorbing Characteristics of Recycled Materials -Based on used Paper and Cigarette Filters- (재생 자원의 흡음특성에 관한 연구 -폐지와 담배필터를 중심으로-)

  • 최창하;조해용;이주민
    • Journal of Environmental Science International
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    • v.10 no.1
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    • pp.9-12
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    • 2001
  • In this study, development of new sound absorbent which is safety, economical and efficient with using recycled materials is tried for substitution of commercial sound absorbent. The sound absorbents, used in this investigation, were made of used paper or filters of cigarette butts. With the variation of the material densities, sound absorptions of materials were measured. The impedance tube method is used for measuring sound absorption coefficient of the new sound absorbent materials. The measured frequency range was 250Hz to 4000Hz in 1/3 octave band. The sound absorption coefficient of the commercial materials and that of the materials synthesized in the our laboratory show almost same value.

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A Study on the Reduction Characteristics of Floor Impact Sound Insulation Due to the Ceiling Frame Structures in Apartment Houses (공동주택의 천장틀구조 변화에 따른 바닥충격음 차음특성 연구)

  • 정환욱;기노갑;송민정;김선우
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.8
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    • pp.573-580
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    • 2002
  • Generally the ceiling frame of apartment house is made of wood. But the wood frame has several problems due to the natural properties such as distortion by shrink, low fire resistance and material loss in the construction field. And it has some defections in sound insulation performance. Therefore it is necessary to develop a new method that can be used as a ceiling frame. This study aims to analyze and to compare the sound insulation characteristics against the floor impact sound between wood ceiling frame and M-bar frame which is made of steel. The results of this study are like these. M-bar frame is more effective than wood ceiling frame in sound insulation. And sound absorbing or sound insulation materials which can be Put on gypsum board are helpful to improve floor impact sound insulation performance.

Study on the Sound Absorption Properties of Noise Barrier according to the Compositions of Absorptive Material (흡음재 구성방법에 따른 방음벽의 흡음특성에 관한 연구)

  • 김경우;양관섭;강재식;이승언
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.05a
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    • pp.1222-1227
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    • 2002
  • Noise barrier is used to reduce traffic noise. The effect of a noise barrier depends not only on the materials, but also on the physical properties such as density, height and degree of absorption, etc. Typical absorptive noise barrier is used sound absorbing material, such as glass wool and mineral wool. The goal of this study is to develope excellent absorptive noise barrier using a polyester. Laboratory measurements were peformed with various thicknesses, density and layer of absorber in a reverberation room.

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A Study on Organic-Inorganic Hybrid Sound Absorbing Materials Using by Recycling Gypsum (재활용 석고 부산물을 이용한 유무기 하이브리드 흡음재 개발 연구)

  • Shin, Hyun-Gyoo;Jeon, Bo-Ram;Ha, Joo-Yeon;Jeon, Chan-Soo
    • 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.

Experimental Study on the Effects of Combustion Products on the Human Body and Suggestion of Law Revision (흡음재의 연소 생성물이 인체에 미치는 영향에 대한 실험적 연구 및 법률 개정 제언)

  • Kang, Jung Ki;Choi, Don Mook
    • Fire Science and Engineering
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    • v.33 no.4
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    • pp.28-34
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    • 2019
  • Regardless of the ignition source, the main factors affecting the spread of flames to the human body are combustibles. The sound absorption material, which is the finishing material used in music institutes and karaoke rooms, consists of polyurethane that generates a large amount of toxic gas with a high amount of combustion gases during a fire. Still, the current law does not require the use of impregnated finishing materials for tutoring services with less than 100 users. In this study, the rate of flame diffusion was measured using the MultiRaelite composite gas measuring instrument (target substance VOC, HCHO, SO2, CO2, CO, HCN, and NO2) for the collection of sound-absorbing materials installed in the actual music academy. The results showed that the toxic gas found in this experiment exceeded the allowable concentration of TWA (Time Weighted Average) and STEL (Short Term Exposure Limit). In addition, a comparative combustion test of the general sound absorber and non-combustion sound absorbing materials on the market showed wide differences in ignition and diffusion. Therefore, based on the results of the experiment, private institutes with less than 100 users should be mandated to use non-combustion sound absorbing materials.