• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1342-1351
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• 2011

Nowadays rolling stock has become a fast and convenient transportation and increased in its demands. But the improvement of speed has result in increase of aerodynamic noise and therefore residential districts near by the railroad are now constantly suffering from the racket. Thus the study regarding rolling stock's environmental noise measurement and appraisal has become important. The case of environmental noise, there are no changes of tone so prediction can be made by reducing areas around the railway. This is part of the study which estimates the noise around the railway using scaled model, and the source of the noise has been researched on. The scaled model of rolling stock will have to be able to make high frequency and it needs to be spread out in a short amount of time. When popping a balloon or firing a gun fits its condition and this study analyzed the characteristics of these two different noises. Measurement was held on a wide vacant lot and the reflection effect of the ground is additionally examined. It is judged to be used in the future when predicting the environmental noise of railway vehicles.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.754-760
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• 2008

For monitoring of railway structures, optical fiber sensors are very convenient. The fiber sensors are very small and do not disturb the structural properties. They also have several merits such as electro-magnetic immunity, long signal transmission, good accuracy and multiplicity of one sensor line. Strain measurement technologies with fiber optic sensors have been investigated as a part of smart structure. In this paper, we investigated the possibilities of fiber optic sensor application to the monitoring of railway structures. We expect that the fiber optic sensors have much less noises than electrical strain gauges because of electro-magnetic immunity while railways operate electric power of 22000 volts. Fiber optic sensors showed good durability and long term stability for continuous monitoring of the railway structures as well as good response to the structural behaviors during construction.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.3
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• pp.335-344
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• 2008

In recent years, public complaints against railroad noise by KTX and Ordinary train have been rising. Regulation of railways noise uses same standard without distinguishing the type of railroad cars. According to the type of railroad cars, the frequency characteristics of emitting noise is different. Therefore it is requested to know how the public response vary to each types of railroad cars. The noise annoyance from three types of trains(KTX, electric train, diesel train) was analyzed by jury evaluation test for assessing the effect of frequency characteristics. The numerical results by a semantic differential method showed that annoyance response to three type of trains depended on the frequency characteristics. As a result, this study proposed that the KTX could have a bonus level of maximum 2.9 dB(A) compared to ordinary train.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2008.03a
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• pp.51-68
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• 2008

When the train enters into a tunnel a high speed, pressure waves are generated inside the tunnel. The pressure waves at propagate in a form of compression wave toward the tunnel exit and a fraction of the compression waves that arrives at the exit of the tunnel are discharged to outside of the tunnel and the remainder is reflected into the tunnel as expansion waves. The compression waves emitted from the tunnel does not radiate in a specific direction but in all directions. If the amplitude of the compression wave is great, it causes noise and vibration, and it is called "Micro-Pressure Wave." "Micro-Pressure Wave" must be considered as a decision for the optimum tunnel cross-section as the amplitude of the compression wave depends on train speed, tunnel length, area of tunnel and train. Therefore, this paper introduces the case study of Micro-Pressure Wave characteristics for determination of tunnel cross section in Honam high speed railway, the pressure inside the tunnel and the micro-pressure waves at tunnel exit were measured at Hwashin 5 tunnel in Kyungbu HSR line. At the same time. a test of train operation model was performed and then the measurement results and test results were compared to verify that the various parameters used as input conditions for the numerical simulations, which were appropriate. Also a model test was performed, in order to analysis of the Micro-Pressure Wave Mitigation Performance by Type of Hood at Entrance Portal.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.150-157
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• 2011

Nowadays, high speed train has settled down as a fast and convenient environment-friendly transportation and it's need is gradually increasing. However increased train speed leads to increased aerodynamic noise, which causes critically affects comfortability of passengers. Especially, the pantograph of high speed train is protruded out of train body, which is the main factor for increased aerodynamic noise. Since aerodynamic noise caused pantograph should be measured in high speed, it is difficult to measure it and to analysis aerodynamic noise characteristics due to the various types of pantograph. In this research, aerodynamic noise of pantograph is predicted by CFD (Computational Fluid Dynamic) and FW-H (Ffowcs Williams-Hawkings) equation. Also, Wind tunnel test results and numerical simulation results were compared. As a result, Simulation results predicting sound pressure level is very similar with wind tunnel test result. This research will draw major factor in aerodynamic noise of pantograph and will be utilized for predict sound pressure level of pantograph.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1590-1597
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• 2007

This paper deals with the noise source localization of the Korean High Speed Train (KTX) at the speed of 300 km/h. Using Microfonarray system and beamforming technology typical pass-by noise sources and their frequency characteristics are investigated. It is primarily aimed at investigating the location and characteristics of the high speed train emission. The results from the microphone array tests are also analyzed in relation to the remarks from analytic studies and experimental investigations on the high speed train that have been done with the intention of understanding the interior noise mechanism. The acoustical image shows the low frequency noise sources mainly at the position of the under part of the train at high speeds and the related source mechanism are discussed.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.73-80
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• 2007

In this paper, the characteristics of noise and vibration of high speed train is analyzed depending on its speed. The speed is a very important parameter because it can affect the interaction between the train and the environment as well as the characteristics of the train itself. To measure its characteristics, we analyzed the signals from microphones and accelerometers which were attached to the passenger car of the high speed train. The signals from each sensor were stored in the recorder, and then analyzed by using the signal processing program. The data from each sensor are analyzed with the spectrogram. From the spectrogram, we found some distinct characteristics of the passenger car. Also, the characteristics of the noise propagation were inferred from the spectrogram.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1026-1032
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• 2010

In this paper, To estimate the train exterior noise and environment noise which are occur when High-Speed EMU is driving with the speed of 370km/h, Estimated sound source about noise that is appeared during operation based upon noise SPL values. Based on aero-dynamic noise source and wheel-rail noise source, these were already used to the existed research, we have estimated each sound power about measured noise, and computed the sound source to apply on the High-Speed EMU, and also calculated the sound power in case of the maximum operation speed of 370km/h.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.970-978
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• 2010

In this study, interior noise of the high speed EMU was estimated by statistical energy analysis (SEA) method. Based on the data measured at a distance of 25m from a running train, exterior noise of the running train was calculated. And then it was designed as noise sources in VA ONE, a commercial software of SEA. coupling and damping loss factor of high speed EMU studied in previous studies is used. The interior noise of the train was estimated for a open-land section. The analysis of interior noise of HST in the tunnel section will be estimated through same method.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.90-94
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• 2007

There are the high-speed train of two types in Korea, KTX and KHST(Korean High Speed Train). The characteristics of interior noise appear differently because the car bodies of the trains are designed with the different materials. In this study, we measure the interior noise for KTX and KHST. The experimental results show that the interior noise of KTX is equal to KHST in open territory and tunnel and interior noise in tunnel with concreted track increase about $3{\sim}4dB(A)$ compared to tunnel with ballasted track. We also know that interior noise level of KHST is higher then KTX in range of high frequency (above 630Hz).