• 소음진동
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• 제6권5호
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• pp.635-644
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• 1996

In this paper, Allard's modelling method which employs the method of acoustic transfer matrix(ATM) is applied to yield more precise results in the analysis of porous sound absorbing material. The method of ATM, based on Biot's theory, is known to play an important role in the estimation of the sound absorption when a sound projects onto the material. In the case of a single layered porous sound absorbing material, the surface impedance and the absorption coefficient by using the method of ATM are estimated. With the variation of the material properties, sound absorption characteristics and analyzed. Transmission Loss in a combination of the porous sound absorbing material with a thin plate is predicted.

• 설비공학논문집
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• 제25권3호
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• pp.119-125
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• 2013

IInsulation material is generally used for preventing heat loss from heat transport fluids, and water absorption severely reduces the insulation property. The purpose of this study is to evaluate the amount of water absorption supplied by the pouring method and spraying method, to investigate the effects of water absorption on the thermal conductivity of an insulation material, and modeling the relation between water absorption and thermal conductivity. E-glass, a kind of glass fiber, and HYPERLITE, mainly composed of pearlite, are selected, to compare hygroscopic and insulation properties. E-glass is found to have much higher water absorptivity, compared to HYPERLITE. The thermal conductivity of the water-absorbed E-glass is increased by more than 150%, compared to that of no absorption, while variation of the thermal conductivity of HYPERLITE with water absorption is insignificant. A three-stage model of water absorption for thermal conductivity is developed, and the modeling results are found to be in good agreement with the experimental data.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.387-392
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• 2003

This study is put a focus on the identification of sound characteristics according to the interior configuration of sound absorption material and air gap. Noise barrier is general consists of front perforated panel, air layer, sound absorption material, air gap and back plate. Noise barrier is required to the NRC value of 0.7. The absorbing performance of the noise barrier relies on the opening ratio of the perforated panel and the efficiency of the absorbing material. This study has observed the effect of opening ratio and hole size, the increase of sound absorbing performance by the configurations of sound absorption material and air gap. New designed noise barrier is achieved the acoustical performance of 0.87 the measurement in a reveration room.

• 한국소음진동공학회논문집
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• 제23권4호
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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.

• 비파괴검사학회지
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• 제36권3호
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• pp.175-180
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• 2016

Nondestructive evaluation for material health monitoring is important in aerospace industries. Composite laminates are exposed to heat cyclic loading and humid environment depending on flight conditions. Cyclic heat loading and moisture absorption may lead to material degradation such as matrix breaking, debonding, and delamination. In this paper, the moisture absorption ratio was investigated by measuring the Lamb wave velocity. The composite laminates were manufactured and subjected to different thermal aging cycles and moisture absorption. For various conditions of these cycles, not only changes in weight and also ultrasonic wave velocity were measured, and the Lamb wave velocity at various levels of moisture on a carbon-epoxy plate was investigated. Results from the experiment show a linear correlation between moisture absorption ratio and Lamb wave velocity at different thermal fatigue stages. The presented method can be applied as an alternative solution in the online monitoring of composite laminate moisture levels in commercial flights.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.645-648
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• 2005

The grounds of multipurpose practical use degree are built much holding world cup 2002 but material that is used in this building most external membrane ceiling is accomplishing PTEE A master and servant. Therefore, this research analyzed assessment about sound absorption special quality that measure ventilation quantitys of 10 act material and analyze correlation with Air Permeability and the sound absorption rate, and follow in change of layer of air of inside facts material. Result is as following. When Air Permeability good dimension is 5$\sim$15 cc/cm$^2$/sec and acoustic absorptivity is the best as Air Permeability result that measure acoustic absorptivity of inside facts material particularly firstly, could know 8$\sim$9 cc/cm$^2$/sec love. When establish sound absorption inside facts in external membrane as result that measure acoustic absorptivity of inside (acts material secondly, could know that acoustic absorptivity is good though become about minimum back layer of air 900mm.

• Journal of the Korean Wood Science and Technology
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• 제50권3호
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• pp.186-192
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• 2022

This study examined the utility of pine (Pinus densiflora) pollen cones as an environmentally friendly material with sound-absorbing properties. Pine pollen cone samples with widths of 0.8-1.2 cm and lengths of 3.5-4.5 cm were prepared. After filling impedance tubes to heights of 6, 8, 10, or 12 cm with the pine pollen cones, the sound absorption coefficient of the pine pollen cones was investigated. The peak sound absorption frequency of the samples with a thickness of 6 cm was reached at 1,512 Hz; however, this value shifted to 740 Hz in samples with a thickness of 12 cm. Therefore, the sound-absorbing performance of pine pollen cones at low frequencies improved as the material thickness increased. According to KS F 3503 (Korean Standards Association), the sound absorption grade of pine pollen cones ranges from 0.3 to 0.5 M, depending on the material thickness of the pine pollen cones. In conclusion, the pine pollen cones demonstrated good sound absorption properties. They, thus, may be considered an environmentally friendly sound-absorbing material.

• 폴리머
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• 제25권3호
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• pp.427-434
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• 2001

폴리에스터를 이용하여 새로운 자동차용 흡음재를 개발하였다. 흡음의 효과를 최대화시키기 위하여 PET 섬유의 크기를 3과 15 denier로 달리하여 3개의 층으로 제작하였으며, 이때 각층의 중량을 조절하여 밀도를 변화시켰다(895~1790 g/$cm^2$). 또한 PET흡음재의 상업성을 알아보기 위하여 시판하고 있는 glass wool로 제조된 흡음재와 비교 분석하였다. 새로운 PET흡음재는 시판되고 있는 glass wool 흡음재보다 저주파와 고주파대역 모두에서 더 우수한 흡음성능을 보여주었다. 또한 PET흡음재의 밀도와 두께가 흡음성능에 중요한 영향이 있으며, 최적화된 PET흡음재는 시판되고 있는 흡음재와 비교하여 NRC (noise reduction coefficient)가 약 22-39% 향상되었다. 따라서 PET는 성능은 물론이고 환경과 재활용혈에서 glass wool을 충분히 대체할 수 있으리라 생각한다.

• 한국전기전자재료학회논문지
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• 제28권2호
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• pp.75-79
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• 2015

Ti was deposited on the Al substrate using DC magnetron sputtering with changing the $N_2$ gas for the possible application of a solar absorbing layer. $N_2$ gas ranged from 50 to 75 sccm was systematically applied in the 5 sccm interval and the variation of the absorption rate was investigated. Microstructural examination and elemental analysis indicate that Ti was reacted with $N_2$ gas and formed $TiNO_x$ compound. As compared with the film without any exposure of $N_2$ gas, absorption rate improved by more than 20%. Typically the average absorption of $TiNO_x$ fim with 65% of $N_2$ gas was about 99% in the visible range, and the average absorption was more than 90% in the infrared absorption region respectively.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.65-71
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• 2001

Absorbers such as porous materials and panels have limited absorption characteristics to some frequency bands. There is a need for absorbers with high absorption coefficients in a wide frequency ranges to make good response of room acoustics. This is almost impossible for a single absorption material. Composite absorption structure with cover, porous material. and air gap is known to have those wide frequency characteristics. In this basis. various composite absorption structures are measured and investigated as wide range absorption structures. Measurements are performed according to an international standard, ISO 354. Various surface types such as wooden slits, wood/steel perforated panels are selected as surface covers, and also various porous materials such as polyurethanes, polyesters, and glasswools are used inside the covers. Result shows that the area of void parts of surface materials is critical to high frequency absorptions, and thickness of air gaps are critical factor of the peak absorptions of low frequency bands.