• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1193-1196
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• 2003

Noise reduction effect of a pine tree which was used to reinforce a noise barrier was studied by using reduced scale model test. The result show that the pine tree itself was less effective but the combination of pine tree and noise barrier was good for reducing the noise and sight.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.3
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• pp.144-151
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• 2002

This work focuses on finding out the noise source and the method of reducing the noise level of LPG(liquefied petroleum gas) fuel injector. The noise of LPG injector in operating condition is due to the impact between valve and valve seat. This study shows that if the revolution of engine is increased, the noise of LPG injector will be more serious but it is not nearly affected by the increment of fuel pressure. The source and transmission paths of noise are identified through the analysis of noise generation mechanism and noise spectrum. The sound absorbing material is tested to verify its efficiency of sound absorption thor the LPG injector. The effect of noise reduction of absorbing material is remarkable when the engine speed is high. Consequently two methods of reducing the noise level are suggested from the identified results. The one is to equip the absorbing material on the outer side of injector and the other is to coat with a soft material or equip a soft ring on the surface of impact.

• Proceedings of the IEEK Conference
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• 2000.11d
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• pp.81-84
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• 2000

Cellular automata are discrete dynamical systems whose behaviour is completely specified in terms of a local relation. If cellular automata convergence to fixed points, then it can be used to image processing. From the generalized Potts automata point of view, we propose in this paper a cellular automata technique for reducing image noise. To minimize blurring effect, an algorithm based on neighborhood median computation is Preferred. Experimental results are reported.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.368-372
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• 2002

Since rolling (Radial AC Tilt) motion in Optical Pickup Actuator causes RF signal degradation, many researches have been done to find out how to reduce rolling degree. This paper aims to introduce two methods of reducing rolling degree with their theoretical concepts and experimental results. First method rearranges magnetic circuit and the other one adjusts the proportion of the distances among mass center, actuating center and supporting center.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.737-742
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• 2007

The method of the reducing duct noise can be classified by passive and active control techniques. However, passive control has a limited effect of noise reduction at low frequencies (below 500Hz) and is limited by the space. On the other hand, active control can overcome these passive control limitations. The active control technique mostly uses the Least-Mean-Square (LMS) algorithm, because the LMS algorithm can easily obtain the complex transfer function in real-time particularly when the Filtered-X LMS (FXLMS) algorithm is applied to an active noise control (ANC) system. However, the convergence performance of the LMS algorithm decreases slightly so it may delay the convergence time when the FXLMS algorithm is applied to the active control of duct noise. Thus the Co-FXLMS algorithm was developed to improve the control performance in order to solve this problem. The Co-FXLMS algorithm is realized by using an estimate of the cross correlation between the adaptation error and the filtered input signal to control the step size. In this paper, the performance of the Co-FXLMS algorithm is presented in comparison with the FXLMS algorithm. Simulation results show that active noise control using Co-FXLMS is effective in reducing duct noise.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.3 no.1
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• pp.20-26
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• 2000

In order to propose the design and installation information of vegetation belt, field investigation were carried out in the noise pollution control facilities of highway and the streets of a city for two years(1998~1999), and field tests were performed to analyze the noise attenuation effect of them. The noise pollution control facilities were generally classified into three types (noise barrier and vegetation belt type, mounding and vegetation belt type, vegetation belt type only). Most soundproof facilities were proved the noise reduction effects. But according to width, height, structure, auditory distance and planting forms of them, difference of noise reduction effects were investigated. The soundproof facility was suitable the mounding and vegetation belt type in the consideration of road environment, and the installation standard of vegetation was estimated that the width of vegetation was at least 20m and the length of that was 2 times in the distance from noise source.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.924-928
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• 2002

Response of the rail surface is an important factor for the train safety and comfortable travel, and evaluation of vibration at the area along a rail is an important factor for the vibration. The dominant method to reduce the vibration that reach the ground is installing vibration absorber between rall and the under structure. In this paper, we evaluated the vibration reducing effect of using vibration control sleeper pads to slave and earth at certain distance from the sleepers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.499-504
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• 2012

The high-speed train enjoys widespread acceptance as environment-friendly means of medium- to long-distance transportation. The pursuit of higher speed and lighter weight in railroad vehicles has engendered higher noise level. In particular, the environmental noise places many restrictions in the operation of high-speed railroad vehicles. This research investigates the effect of installing a skirt onto a high-speed train bogie with the top speed of 400 km/hr and using High Speed EMU for the purpose of reducing the environmental noise. In order to analyze the effect of the interior noise and environmental noise due to installation of the skirt, sound level is calculated using the Ray method and Statical Energy Analysis method. The numerical calculation predicts a reduction of approximately 2 dB in the environmental noise level, but at the cost of increase of approximately 2.5 dB in the interior noise level of the vehicle.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4371-4377
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• 2012

In this paper, the structure-fluid coupled analysis is carried out in order to examine the cause of the vibration induced by fluid in the pressure-reducing valves for water. It is confirmed that there is the noise at the area of low frequency of 250Hz by measuring noise at pressure reducing valve. The flow analysis is performed by the commercial software ANSYS/CFX. The flow velocity of about 40 m/s is formed by nozzle effect, and so negative pressure is happened in the pressure reducing valve. The structure analysis is carried out with the load condition of pressure distribution by flow formed in valve. The rubber material at disk is deformed to the extent of closing up flow passage. It is confirmed that the disc deformation which is occurred repeatedly is due to noise and vibration at the pressure reducing valve.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.34-41
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• 2001

Semiconductors performing digital clocking are a main source of radiated emission noise. Therefore, the most secure method of reducing emission noise is to reduce emission radiated from semiconductors; an application of an absorber to the surface of semiconductors is one of these methods, too. However, in reality, it is difficult to achieve as much effect of noise reduction as expected by using only absorber. It is confirmed by experiment in this paper that a loop area within chip has no correlation with radiated emission noise and it is clarified why the existing absorber fails to achieve a satisfactory effect of emission noise reduction. Besides, a new type of chip coating absorber has been developed which can cover up to semiconductor out lead by using ferrite coating material of ferrite/epoxy acrylate substance using only permeability loss out of electromagnetic wave reduction characteristics of materials. As a result of evaluating radiated emission noise by applying this coating absorber to semiconductor device, it could be confirmed that emission noise decreased from about 3 ㏈ up to 20㏈ depending on frequency.