• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.202-203
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• 2013

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.196-197
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• 2012

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1155-1158
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• 2007

To reduce acoustic noise level of an AV projector, primary noise sources of AV projector were analyzed. Based on the analyzed result, methods to control each source are presented and tried. Structure-borne noise can be controlled by anti vibration design of mounting system, and air-borne noise by reducing flow resisitvity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.1
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• pp.95-101
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• 2007

Recently, two phase scheme for removing impulse noise in images is proposed. This algorithms first detect the noise candidates based on the adaptive median filter, and then apply optimizing techniques recursively only to those noise candidates to restore image. Thus the noise detector with high accuracy is important role on this algorithm, In this paper, novel noise detector is proposed, which can detect impose noise with high accuracy while reducing the probability of false detecting image details as impulses. And the method for reducing computational cost of regularization phase is presented also.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.904-907
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• 2002

Optical disk drive device is improved in rotating speed for faster data reading. In the case of CD-ROM, rotating speed is over 10000 rpm in the practical use. As a result of high rotating speed, unexpected effects as like increasing disk fluctuation and acoustic noise are raised by the air friction on the rotating disk and the eccentricity of rotating parts. The overall acoustic noise of running CD-ROM could be classified into two different characterized noise. The first is the structural-borne noise which is generated from vibrating solid body. By the reason, the signal of structural borne noise has very similar to the signal of surface vibrating one. It has dense noise energy at specific frequency region. The other is the air-borne noise which is generated from turbulence or vortex caused by friction between disk and air. The signal of air-borne noise has no dominant peak point at acoustic pressure-frequency domain. The noise energy is widely distributed while comparatively high and large frequency region. The structural-borne noise could be reduced by reducing vibration of structure and in addition it's target reducing frequency is narrow. However the air-borne noise reduction is effectively needed of enclosing method for the noise source located near the disk surface because it is difficult to define target frequency point. In this study, the acoustic noise at driving CD-ROM is classified by the sides of it's character and tried to reduce the overall acoustic noise.

• 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 Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.55-63
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• 2020

Road traffic noise is a major complaint. Porous pavement (PP) has been proposed as an effective method for reducing road traffic noise, but it has not been applied much due to the lack of quantitative evaluation. In this study, the noise reduction of single-layer porous pavement (SLPP) and double-layer porous pavement (DLPP) was evaluated. The noise was measured using the CPX method, and the driving speed was measured every 10km/h from 50km/h to 80km/h. The differences in noise level between the two PPs were statistically significant. The driving speed had no significant effect on the difference in noise between the two PPs. The DLPP showed a 6.6dB(A) reduction in average and a 6.3dB(A) reduction at the 95% confidence level compared to the SLPP. Reducing noise by 5dB(A) is equivalent to reducing traffic to 1/3 or lowering the vehicle's speed to 1/2. Sensitively, it is possible to recognize a 3dB(A) and 5dB(A) difference. The DLPP and SLPP were very effective in reducing traffic noise.

• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.691-697
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• 2022

In this work, a straightforward component design of a direct current (DC) relay equipped in electric vehicles is discussed. The work aims to provide and evaluate effective measures for reducing high-frequency sound from the DC relay carrying electric power. From the operation experiments for the relay, it is observed that noise is caused by the resonance from the forced vibration by the electromagnetic repulsive force originating at the area of electric contacts with a resonance frequency of around 710 Hz ~ 730 Hz. A finite element model for the relay was established to conduct vibration mode analysis, consisting of stationary and movable contacts and a contact spring. Vibration mode analysis indicates that in the resonance frequency, the movable contact with two-point contacts experiences rotational vibration mode. For the proposed relay with a three-point contact, vibration mode analyses give reasonable results of reducing noise at that frequency. Furthermore, for the fabricated relays with the three-point contact, similar results have been obtained. In conclusion, one can see that the proposed measures provide one of the feasible solutions to the reduction of relay noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.119-123
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• 2013

We conduct the research for reducing aeroacoustic noise occurred when a vehicle operates in high speed situation without modifying the structural configuration such as deforming A-pillar's side curvature. We introduce PAU (Pneumatic Auxiliary Unit) which is a sort of air duct using intake air through radiator grill. According to our research, we can reduce overall noise levels around the surface of HSM (Hyundai Simplified Model). When a vehicleruns 100km/s, area-weighted acoustic power level (AWAPL) indicates 33dB without PAU. However with PAU, coverall AWAPL is decreased to 29dB which means we can improvesilentness approximately 12% compared to ordinary case. Moreover we conduct similar implementation to steering situation especially about yawing. In varioussituations, -10, 0, 10 degree of yawing, we observe 10% reduction in the upstream region of HSM but little increase in downstream region. It seems that inlet air overlap turbulent kinetic energy to surrounding flow. Even though downstream region's noise is louder than upstream region, overall AWAPL is still lower than conventional condition. We also apply this scheme to the real vehicle situation, then we get reasonable output which can support our research outputs.

• Journal of Auto-vehicle Safety Association
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• v.13 no.3
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• pp.32-40
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• 2021

Composite material is very attractive because it has excellent mechanical property and is possible to lightweight due to the low density. However, composite material is less used compared to other systems in the chassis system because it is very hard to solve NVH problem when composite material is applied to vehicle. Especially, reducing squeal noise of composite brake system is essential to apply it to vehicle successfully. In this paper, we present a new solution to reduce squeal noise of composite brake system. To achieve this goal, we analyze main causes of noise using RCA (Root Cause Analysis), CA (Contradiction Analysis) and sequentially get IFR (Ideal Final Result) to solve the problem. Next, we define the function of composite brake system and derive control factors and noise factors. A variety of tests for factors like chamfer, slot, damping shim, underlayer of brake pad are done. In addition, we analyze level of contribution for control factors theoretically. Finally, we get the effective solution for reducing squeal noise.