• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.568-571
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• 2004

This research estimated the physical. mechanical characteristic and the character of sound absorption according to target void ratio of porous concrete and the mixing ratio of recycled aggregate for the valid utilization of recycled aggregate using waste concrete and sound reduction out of a road, a railway, a residential street, and a downtown area. As a result of the test, compressive strength tended to be a radical strength fall when target void ratio was $25\%$ and contents of recycled aggregate exceeded over $50\%$. Also, the character of sound absorption of porous concrete which used recycled aggregate using waste concrete was the most excellent when target void ratio was $25\%$, and the influence by contents of recycled aggregate was trivial. Therefore, when the strength and the character of sound absorption of porous concrete are considered, it is proved valid that proper target void ratio was $25\%$ and contents of recycled aggregate using waste concrete was $50\%$ or so.

• 한국소음진동공학회논문집
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• 제20권10호
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• pp.983-990
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• 2010

Reduction of acoustic loads of space launch vehicles can be achieved by acoustic absorbers satisfying strict cleanness requirements. This limited the use of general porous materials and requires non-porous sound absorbers. Micro-perforated panel absorbers(MPPA) is one of promising sound absorbers satisfying the cleanness requirement for launch vehicles. However, its applicability was limited to low sound pressure levels according to the acoustic impedance model of micro-perforated panels. In this paper the applicability of micro-perforated panel absorbers at high incident sound pressure was investigated in experimental ways. The absorption characteristics of a micro-perforated panel absorber was simulated according to its design variables, e.g., minute hole diameters and aperture ratios. It was shown that optimal design can be readily done by using proposed design charts. Experiments were conducted to measure acoustic properties of the designed micro-perforated panel absorbers. The results showed that acoustic resistance increases rapidly as incident sound pressure level does but change of acoustic reactance can be neglected in a practical point of view. This caused the decrease of peak value of absorption coefficient at high incident sound pressure level, but the amount of reduction can be accepted in practice. The major advantage of the micro-perforated panel absorber(wide absorption bandwidth) was still kept at high sound pressure level.

• 한국공간구조학회논문집
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• 제11권1호
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• pp.67-75
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• 2011

본 연구는 컴퓨터 시뮬레이션을 이용하여 대공간에서 스피커 시스템의 변화에 따른 음장의 특성 변화를 검토하였다. 실의 음향특성변화는 실의 흡음력과 동시에 스피커 시스템의 지향성, 설치높이 및 개수를 조절하면서 예측 분석하였다. 연구 결과, 명료도 관련 지표인 D50 및 RASTI는 실의 흡음력 증가의 변화를 효과적으로 나타내는 것으로 분석되었다. 또 초기감쇠시간은 흡음력 증가에 따라 선형적으로 감소하였으나 저 고주파수대역에서는 오히려 증가하거나 변화를 보이지 않았으며, 잔향시간은 전체주파수대역에서 실의 흡음력 증가에 따라 감쇠하였으나 주파수대역별 결과에서는 오히려 증가하거나 비슷한 결과를 보였다. 이는 실의 음향특성이라기 보다는 감쇠구간의 비선형성에 기인한 것으로 판단된다. 스피커 시스템의 적용에 따른 분석결과, D50 및 RASTI는 실의 흡음력 증가에 크게 상관없이 거의 모든 시스템에서 'fair'이상으로 평가되었으며, 스피커의 설치위치가 높을수록 실의 흡음력 증가보다 스피커 지향특성 변화에 더 큰 영향을 받는 것으로 나타났다. 또한 스피커의 설치위치가 낮을수록 실의 잔향시간은 더 짧은 것으로 분석되었다. 시스템의 적용에 따른 잔향시간은 스피커 설치높이가 높을 경우 실의 흡음력 증가에 비례하여 감쇠하는 경향을 보였으나 스피커 설치높이가 낮은 경우 흡음력 증가에 의한 영향보다 시스템의 영향을 받는 것으로 나타났다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1002-1006
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• 2000

It is diffuse sound field that measuring condition of absorption ratio and sound transmission loss for material consist of building are measured in reverberartion room and on-site. In this study, for upkeeping diffuse sound field in reverberation room, it is measured and etimated that sound field is effected according to sound source lacation and characteristics of emission directivity for sound source.

• 한국소음진동공학회논문집
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• 제21권9호
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• pp.850-857
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• 2011

Generally, sound-absorbing materials in vehicles are used for giving the comfort to passengers by reducing noise while driving. Materials of which targets are light weight, high performance, eco friendliness and recycling have been developed recently. In this study, sound-absorbing materials using PET(polyethylene terephthalate) hollow fibers to achieve the light weight and the high sound absorption performance are developed, and then evaluated to meet a requirement for the automotive components. The test results show that the acoustic performances of developed products having new fiber structure are better than those of the conventional product.

• KIEAE Journal
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• 제6권1호
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• pp.11-16
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• 2006

This paper deals with the experimental for manufacturing the lightweight buildng materials with portland cement, fly ash, slag, lime, gypsum, and aluminum powder system. Aluminum powder was added an aerating agent. Specific gravity range of lightweight concrete specimens were 0.6~0.9g/cm3. These specimens properties studied by means of specific gravity, compressive strength, absorption coefficient, transmission loss and scanning electron microscopy. Cellular concrete with maximum compressive strength was 41kgf/cm2 by obtained Al=0.05wt.%. Moreover, the aeration lightweight concrete showed excellent sound absorption properties.

• 한국소음진동공학회논문집
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• 제13권9호
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• pp.730-734
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• 2003

For the noise reduction measures in a construction field or near the traffic line receiver is often the most economic measure in order to exclude the propagated sound. The dimension of the barrier is decided by the noise and construction design, and the constructive quality of a soundproof panel shall be secured in accordance with KS F4770 to guarantee the safety of sound barriers. In this paper the problems included in the KS F4770-1 that is the regulation for the metallic sound barrier of the absorption type are identified and it is suggested what to be corrected or improved. Through a series of the analyses, conclusions were reached that it is required to improve test methods in KS F4770-1 as well as to break down test loads for building more cost-effective sound barrier.

• 소음진동
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• 제7권5호
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• pp.781-787
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• 1997

A new method is presented to determine two fundamental acoustic quantities of sound-absorbing materials such as characteristic impedance and propagation constant. In this study, the surface acoustic impedances of sound-absorbing materials are measured using the impedance tube and the anechoic chamber to determine the above acoustic quantities. The measured results are given for two typical sound-absorbing materials(glass wool and urethane foam) int the frequency range between 150 and 1, 600 Hz. The results are verified by other two known methods, which are Smith & Parrott method and Utsuno et al. method. The absorption coefficients calculated from the empirical models(Miki model for glass wool and Jung model for urethane foam) and two quantities by present method are in good agreement with the measured values.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.457-460
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• 2004

This study examines the sound insulation of the light-weight wall using light-weight concrete and offers the basic datum for enhancing it. The sound insulation of the light-weight wall is determinated by the density, installation method, absorption materials, air layers etc. Among the factors, the solution of outlet that is the major cause of reducing sound insulation should be made. If absorption materials are installed in the cavity walls, it enhances to 15dB in 500Hz.

• 한국음향학회지
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• 제36권4호
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• pp.254-260
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• 2017

본 연구는 만석 객석의자 등의 흡음특성 시 활용될 수 있는 표준더미 개발을 위한 기초연구로서 착의량에 따른 인체의 흡음특성을 잔향실법 측정방법을 이용하여 평가하였다. 측정방법은 기존 연구(Conti et al., 2004)에 따라 잔향실 중앙에 1인의 피험자가 서 있는 조건에서, 다양한 소재의 의복착용에 따른 주파수 대역별 흡음면적을 측정하였다. 측정 결과, 겉옷을 제외한 상하의를 착용하였을 때 전주파수대역 평균 흡음면적은 피험자에 따라 $0.25m^2-0.48m^2$의 분포를 보였고, 외투 착용에 따라 $0.38m^2-0.98m^2$의 분포를 보였다. 섬유소재에 따라 폴리에스터 류의 겉옷은 800 Hz - 1 kHz 대역에서 피크 특성을 보였고, 모나 면 소재의 겉옷은 고주파수 대역으로 갈수록 흡음면적이 높아지는 특성을 보였다. 착의량에 따른 흡음면적의 변화는 착용한 의복의 열저항(clo)과 체표면적당 무게로 구분하여 비교하였다.