• Journal of KSNVE
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• v.10 no.4
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• pp.662-668
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• 2000

Sound transmission characteristics are investigated on the aluminium extruded panels used for railway vehicles. An equivalent orthotropic plate model and mass law are applied to predict the sound transmission loss. An extruded panel specimen used in the floor of railway vehicles is manufactured and is tested to measure sound transmission loss by two reverberant chamber method. Predicted transmission loss I compared with measured values and the effect of local resonance on the transmission characteristics is identified. The results are applied to design the extruded panel having better sound insulation performance.

• Journal of KSNVE
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• v.8 no.5
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• pp.807-813
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• 1998

Transmission loss of the simple expansion chamber with multiple inlet and outlet ports is obtained. Transfer matrices which represent the relation between the power variables(pressure and velocity) of inlets and outlets depend on the input relatons as well as the acoustic system parameters(i.e. geometry of the chamber, wall admittance, etc.). The analysis has been performed analytically, including the effects of higher order modes for the 2-inlet/1-outlet, 1-inlet/2-outlet and 2-inlet/2-outlet systems. This study yeilds that phase difference between the inlet ports can significantly increase the transmission loss in low frequency range.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.11
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• pp.1013-1020
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• 2007

In this paper, the predictions and measurements of sound transmission loss(STL) are discussed for various types of acoustical materials and carpets. Random incidence sound transmission losses are measured by the sound intensity method. The in-house software HONUS2005 is used to predict TL and estimate the various physical properties such as the flow resistivity, the structure factor, the porosity, the Possion's ratio, and etc. After this estimation, various multi-layered materials with a steel plate are measured and predicted. In particular, Carpets are assumed to be membranes to predict acoustical performance. To confirm this assumption, double and triple-layered cases are also observed including two different kinds of carpets.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.694-698
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• 2004

The importance of insulating material becomes greater recently in order to attain a quieter life style amidst today's sound noise such as transportation, industrial machinery. The demand for insulating material is increasing due to the increase of noise space. It is reasonable to predict the transmission loss and the absorption of the insulating Material before arranging it in the appropriate places and attaining a Pleasant acoustic environment inside the space. The experiments of insulating material's were performed using Impedance tube Type 4206 T of B&K, and VIOLINS which is a FEM Program of LMS was used for the analysis

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1267-1268
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• 2015

본 논문에서는 평탄 대역 모드와 손실형 평탄 대역 모드의 투과 스펙트럼을 가지는 PDLS 기반 Lyot형 광섬유 빗살 필터에서 출력되는 편광 상태를 이론적으로 분석하였다. 분석을 위해 파장 가변 레이저, 편광 조절기, 그리고 편광자를 사용하였다. 필터에 배치된 두 개의 반파장판을 적절히 조절하여 평탄 대역 모드와 손실형 평탄 대역 모드를 선택할 수 있다. 편광 조절기를 적절히 조절하면 파장 가변 레이저로부터 나오는 빛의 편광을 원하는 것으로 선택 가능하고 한 채널 내에서 필터의 투과 대역을 미세하게 조절할 수 있다. 그리고 편광자를 통해 출력되는 스펙트럼으로 출력 스펙트럼의 파장별 편광 상태를 알 수 있다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.92-95
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• 2011

The walls of modern train cars are required to have higher transmission loss since modern train have had high speed and light weight. The method based on Reverberation Chamber like KS F 2808 could be used to measure transmission loss. However, this method has difficulty in that constrained Standard of it requires extremely large facilities. Recently, the method based on Scale Reverberation Chamber is used as an alternative to Reverberation Chamber. The method of Scale Reverberation Chamber is known to be small and economical but it provides standing wave that directly influences measurement error. Therefore, this research is focus on predicting standing waves based on method of FFM and reducing measurement error by changing shape of chamber.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.690-692
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• 2014

To identify characterization of a simple extension chamber that have the two internal partition, produce the curve to estimate the transmission loss without the computer analysis. For helpful for internal optimum design, identify the characteristic of internal partition on transmission loss. Made estimated transmission loss curve by function of relationship of internal partition and transmission. Check the similarity of predicted transmission loss and analysis transmission loss. Usage of the predicted transmission loss made by relationship of internal partition and transmission loss is good information to place the internal partition so as to maximize the transmission loss on target frequency at optimal design on muffler.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.687-689
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• 2014

This paper deals with the optimal muffler model by using acoustic analysis and CFD(computational fluid dynamics) analysis. The complicated muffler model could be better noise reduction performance. However, it could be worse affected to back-pressure performance by pressure drop in working fluid. High back-pressure is caused to low system efficiency. Therefore, it is important for the muffler design to consider the pressure drop. The muffler models are changed their partition plate position. Acoustic power transmission loss(TL) and pressure drop of working fluid are calculated by using computational analysis and used to build database for finding their trends. The optimal muffler model in user-interested frequency range could be selected by analyzing this database.

• Journal of the Korean Society for Railway
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• v.10 no.4
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• pp.405-408
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• 2007

In this paper, we describe the analysis of interior noise for tilting train that is being developed in Korea. Tilting train is made of composite material to reduce the car body's weight and attached a self-steering system on bogie to improve curving performance. However, the acoustic performance (Transmission Loss) of such material is worse than the materials of conventional train, such as aluminum, steel and so on. Therefore, we measure the transmission loss of side wall/floor of tiling train and predict the interior noise for tilting train using its measuring results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.178-183
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• 2003

This paper deals with transmission loss characteristics of the panel type silencer to control low frequency noise. The panel type silencer is composed of many Helmholtz resonators by side branch. Each resonator has high transmission loss on the narrow band of its resonance frequency. Direct arrangement of the resonators increases mainly the magnitude of transmission loss. If we arrange the resonators in a row, the peak and band of transmission loss are increased. This makes the resonator array to have high transmission loss in the broader band. Using this idea, we design a silencer that has broader band characteristics and smaller volume.