• 폴리머
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• 제34권5호
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• pp.410-414
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• 2010

재활용 PET와 fly-ash를 이용하여 두 가지 종류의 고분자 몰타르(PMM)를 제조하였다. 재활용 PET의 조성을 변화시켜 경성(rigid) polymer-modified mortar(PMM)와 연성(flexible) PMM을 제조하였다. 마찰계수 측정을 포함하는 기계적 특성과 흡음 특성을 조사하였고 상업적 PMM인 에폭시 PMM과 PET PMM을 비교하였다. 기계적 특성들의 결과로부터 경성 PMM이 상업적인 PET PMM에 비하여 우수함을 알 수 있었다. 흡음계수 측정에서 경성 PMM과 연성 PMM 모두 상업적인 PMM에 비하여 매우 우수한 흡음 특성을 보여주었다. 또한, 마찰계수 측정결과는 경성 PMM이 바닥재의 활용에 적절하다는 것을 보여주었다.

• 한국주조공학회지
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• 제31권3호
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• pp.145-151
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• 2011

Metallic foam has been known as a functional material which can be used for absorption properties of energy and sound. The unique characteristics of Al foam of mechanical, acoustic, thermal properties depend on density, cell size distribution and cell size, and these characteristics expected to apply industry field. Al-Zn-Mg-Cu alloy foams was fabricated by following process; firstly melting the Al alloy, thickening process of addition of Ca granule to increased of viscosity, foaming process of addition of titanium hydride powder to make the pores, holding in the furnace to form of cooling down to the room temperature. Metal foams with various porosity level were manufactured by change the foaming temperature. Compressive strength of the Al alloy foams was 2 times higher at 88% porosity and 1.2 times higher at 92% porosity than pure Al foams. It's sound and vibration absorption coefficient were higher than pure Al foams and with increasing porosity.

• KIEAE Journal
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• 제8권5호
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• pp.3-10
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• 2008

The Korean traditional architecture has developed by adapting to the natural environment, and has successfully created a comfortable indoor settings by using the surrounding natural resources. This is reflected in the building layout, space design and even materials. Our traditional wooden windows adjusting ambient temperature and humidity have both the functions of window and door, although they are clearly divided in the West. The opening and closing method of our traditional windows is similar and their dimensions are shown not to be standardized but diverse in terms of the characteristic of wooden furniture and that of components placed between columns. Thus this study aims to research the sound insulation and absorption performance of traditional windows to be varied with thickness, finishing method of window paper and thickness of air layer. Despite increase of the thickness of window paper, sound absorption was reduced, and the same result was shown when both sides of the structure were finished with thick window paper. The sound insulation performance of the windows could be evaluated to be inappropriate with $R_w$ 0 ~ $R_w$ 14.

• Ocean and Polar Research
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• 제29권2호
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• pp.113-121
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• 2007

The sound wave in the sea propagates under the effect of water depth, sound speed structure, sea surface roughness, bottom roughness, and acoustic properties of bottom sediment. In shallow water, the bottom sediments are distributed very variously with place and the sound speed structure varying with time and space. In order to investigate the seasonal propagation characteristics of low-frequency sound wave in the Yellow Sea, propagation experiments were conducted along a track in the middle part of the Yellow Sea in spring, summer, and autumn. In this paper we consider seasonal variations of the sound speed profile and propagation loss based on the measurement results. Also we quantitatively investigate variation of bottom loss by dividing the propagation loss into three components: spreading loss, absorption loss, and bottom loss. As a result, the propagation losses measured in summer were larger than the losses in spring and autumn, and the propagation losses measured in autumn were smaller than the losses in spring. The spreading loss and the absorption loss did not show seasonal variations, but the bottom loss showed seasonal variations. So it was thought that the seasonal variation of the propagation loss was due to the seasonal change of the bottom loss and the seasonal variation of the bottom loss was due to the change of the sound speed profile by season.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.935-940
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• 2001

This study search for absorbing sound and exhaust-gas which aims to manufacture continuous void by using clay and foam, the surface of materials is covered with $TiO_{2}$ powder as heat treatment. According to the results of the experiment, the increase of thickness of manufactured sound absorbing materials caused the increase of absorption rate in the range of low and middle sound and thus it can be an important factor of improving absorption rate. Sound absorbing materials could satisfy 70% of the average of sound absorption ratio in 7cm thickness. Also, the manufactured sound absorbing materials is covered with $TiO_{2}$ showed an excellency in the clarification of exhaust-gas under ultraviolet rays treatment when 70% of removal rate and about 10% of generation rate of $NO_{2}$ is settled by the flow of 2 $\ell$/min NO gas. Especially, manufactured sound absorbing materials could improve compressive strength of continuos porous concrete. in the case of 7% bubble addition, when the substitution rate of coagulator was 30% and 20%, compressive strength was 45kgf/$cm^{2}$ and 65kgf/$cm^{2}$ respectively. As the substitution rate of coagulator reducing, compressive strength increased after preforming burnt clay.

• 한국소음진동공학회논문집
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• 제15권8호
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• pp.924-930
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• 2005

Sound absorptive materials have good performance in high frequency range, not at low frequencies. Therefore it has been great challenge to develop a sound absorbing structure that is good at low frequency. We propose to use a Helmholtz resonator array panel for this purpose. A Helmholtz resonator is one of noise control elements widely used in many practical applications. The resonator is a simple structure composed of a rigid-walled cavity with a neck, but it has very high performance at resonance frequency. This paper discusses the sound absorption of Helmholtz resonator array panels at normal and random incidence. First, various experimental results are introduced and studied. Secondly, we theoretically predict the absorptive characteristics of the resonator away panel. The theoretical approach is based on the Fourier analysis for a periodic absorber. We believe that this method can be used to design a panel for low frequency noise control.

• 한국공작기계학회논문집
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• 제17권3호
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• pp.122-127
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• 2008

The source of wayside noise for the train are the aerodynamic noise, wheel/rail noise, and power unit noise. The major source of railway noise is the wheel/rail noise caused by the interaction between the wheels and rails. The Structure borne noise is mainly a low frequency problem. The train noise and vibration nearby the elevated railway make one specific issue. The microphone array method is used to search sound radiation characteristics of elevated structure to predict the noise propagation from an elevated railway. In this paper, the train noise and structure borne noise by train are measured. From the results, we investigated the effect on the sound absorption tunnel for elevated railway.

• 콘크리트학회논문집
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• 제16권4호
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• pp.541-548
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• 2004

본 연구는 도로, 철도, 주택가 및 도심지역의 소음저감과 건설부산물로 발생하는 폐콘크리트 재생골재의 유효이용을 위하여 포러스콘크리트의 목표공극률과 재생골재 혼입률에 따른 물리 역학적 특성 및 흡음특성을 평가하였다. 시험결과, 목표공극률과 실측공극률과의 차이는 1.7% 이내로 나타났고 압축강도는 목표공극률이 25%, 재생골재의 혼입률이 50%를 초과하는 경우에는 급격한 강도저하 경향을 나타냈다. 또한, 폐콘크리트 재생골재를 사용한 포러스콘크리트의 흡음 특성은 NRC의 경우 목표 공극률이 25%에서 가장 우수한 흡음특성을 나타냈으며, 재생골재의 혼입률에 따른 영향은 작은 것으로 나타났다. 따라서, 포러스콘크리트의 강도 및 흡음특성을 고려하였을 때 적정 목표공극률은 25%, 폐콘크리트 재생골재의 혼입률은 50% 정도가 유효한 것으로 판단된다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.10-12
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• 2014

In ISO 10140-5:2010, defines the reverberation time conditions of the receiving room. The sound absorption side of test specimen is installed in the source room generally. In this study, examined at the change in the sound insulation characteristics for the test specimen of asymmetric structure attached sound absorbing material by changing the installed position. A difference of sound insulation performance was maxium Rw 1 dB, it is preferable to place the larger sound absorption area in source room.

• The Journal of the Acoustical Society of Korea
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• 제21권2E호
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• pp.81-90
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• 2002

Single absorbing materials and Helmholtz resonators have limited absorption characteristics over limited frequency ranges due to their structures and properties. Porous materials are highly absorptive for mid and high frequency ranges, while they have little sound absorption for low frequency sounds. Helmholtz resonators are generally used to absorb sound energy for a specified frequency range. Hence they have limited capability in controlling the overall acoustic properties of a space. Not much has been known about useful finishing materials which have enough rigidity and absorption over broad frequency range, in spite of wide demands from acoustic designers and consultants. The present work measured and analyzed absorption characteristics of a slit absorber by varying surface materials, depths of air gap, dimensions of slat and slit widths. It was found that the narrower the slit width, the larger the absorptions over the wide frequency ranges and the pattern was dependent on the presence of porous material. Narrower slat's width tend to increase the slit absorber's absorption more or less. Absorption coefficients at low frequency ranges were dramatically improved (from 0.23 to 0.56) by increasing air gap when porous materials were present.