• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.7
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• pp.783-789
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• 2008

This experimental study describes the noise reduction and the feasibility of short current of a silencer for a high voltage COS(cut out switch) fuse of a transformer. When a high voltage COS fuse becomes a short circuit by the over current, the strong impulse noise over 150 dB(A) is generated. For the purpose of the reduction of impulse noise, in this study, the diffuser type and the reactive type silencers have been designed and tested, respectively. And also the electrical test on the short current is performed. From the experimental results, the well designed reactive type silencer has been shown to have the noise reduction of about 20 dB(A). It has been found that the feasibility of short current for the COS fuse is closely related to the porosity of the silencer.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.951-954
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• 2006

This Study introduces the design of a reactive type silencer for reducing impulse noises emitted from a high voltage COS fuse of a transformer. When a high voltage COS fuse becomes a short circuit by the over current, the peak sound pressure level above 150dB(A) is generated at the distance of 2m from a COS Fuse. For the purpose of the reduction of impulse noise, in this study. the reactive type silencers have been utilized. The performance of noise reduction for them can be expressed by insertion loss. The reactive silencers have been tested for 23 different types with each different porosity, hole diameter and depth. From the experimental results, it is found that the reactive silencer has an excellent performance to greatly suppress the impulse noise. The one-stage, two-stage and three-stage reactive type silencers have been shown to have the insertion losses of about from 35dB (A) to 25dB(A).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1415-1418
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• 2007

When a high voltage COS fuse becomes a short circuit by the over current, the impulse noise over 150 dB(A) with the strong pulse jet is radiated from the COS fuse of an electric transformer. For the purpose of the impulse noise reduction, in this study, a reactive type silencer with perforated panels are considered. The transmission loss of the silencer are calculated by transfer matrix method. The effect of the porosity, the distance between panels, and the number of perforated panel on the sound transmission loss is investigated and discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.258-261
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• 2006

This study introduces the control of duration time of impulse noises emitted from a high voltage COS fuse of a transformer. When a high voltage COS fuse becomes a short circuit by the over current, the peak sound pressure level over 150 dB(A) is generated at the distance of 2m from a COS Fuse. For the purpose of the reduction of impulse noise, in this study, the reactive type silencer has been utilized. And also electrical interrupting test was experimented. From the experimental results, the reactive type silencer has been shown to have the noise reduction of about 13 dB(A). It has been found that the electrical interception performance of the COS fuse was related to the control of the duration time of impulse noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.715-721
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• 2008

공동주택에서의 음환경 성능은 실내환경의 질과 연관시켜 설계단계부터 충분한 검토가 필요한 성능항목이다. '국토해양부'는 '공통주택 성능등급 표시제도'에서 Air Duct를 통해 상하층간 전파되는 소음을 제어하기 위한 대책을 요구하고 있다. 이에 화장실에 적합한 구조 및 재질로 소음 저감기를 개발하고, 소음기 성능평가 장치를 구성하여 이론과 비교평가하고, 실제 현장에 설치 시 적용효과를 분석하였다.

• Journal of KSNVE
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• v.9 no.5
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• pp.914-921
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• 1999

There are many theoretical investigations to analyze higher order mode of reactive type single expansion chambers with offset inlet/outlet locations. But the conventional method has the restriction that the ratio between the area of inlet(or outlet) pipe and that of chamber must be natural number. In the paper, a new method was suggested to apply the Kim's method to silencer with circular cross-section. Not only the offset location but also the magnitude of cross-section area of inlet/outlet pipe can be considered by the suggested method. The predictions by this new method also compared with those by the finite element method and Munjal's method in order to verify the accuracy of the suggested method presented here.

• The Journal of the Acoustical Society of Korea
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• v.21 no.5
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• pp.503-509
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• 2002

Cylindrical chamber silencers with an extended inlet and outlet are extensively used in many application fields to reduce the propagated noise in ducts. The basic attenuation effectiveness in the low frequency region can be explained by the reactive wave action inside the expansion chamber associated with the geometric configurations of the inlet and outlet locations, and the area expansion of the jacket. In this study. an acoustic analysis is carried out for a concentric extended pipe inserted into a simple expansion chamber. An algebraic equation is derived by using the eigenfunction expansion and orthogonality principle in which the acoustic pressures and particle velocities defined on each subdivided surface are expressed by the separable coordinates. By using the proposed analytical method, transmission losses are predicted for several configurations of the concentric extended systems and they agree very well with experimental results.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.24-30
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• 1998

A directly coupled Boundary Element and Finite Element Model was applied to the dynamic analysis of a coupled acoustic silencer with vibratory wall. In this cupled BEM-FEM muffler model, the BEM model was used to discretize the acoustic cavity and the FEM model was used to discretize the vibratory wall structure. Then the BEM model was coupled with the FEM model. The results of the coupled BEM-FEM model for the dynamic analysis of the simple expansion type reactive muffler configurations with flexible walls were verified by comparing the predicted results to analytical solutions. In order to investigate the effects of the muffler's structural flexibility on its transmission loss(TL) characteristics, the results of the coupled BEM-FEM model in conjunction with the four-pole parameter theory were utilized. The muffler's TL characteristics using the BEM-FEM coupled model with flexible walls as compared to other muffler configurations was studied. Finally the muffler's TL values with respect to different wall's thickness are predicted and compared.