• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.23 no.1
• /
• pp.65-72
• /
• 2013

This case study presents a practical method to reduce resonant vibration of large vertical pumps. The pumps are driven at 400 rpm rated speed by induction motor. The vibration was not significantly large when operated at this rated speed. Large vibration was occurred when the pump was operated below the rated speed for flow control. Due to the large vibration resonance, variable speed operation of the pump was not possible for several months at worst cases. To find an efficient vibration control method, the flexural responses of pumps for both normal and transient operations were measured. The measured modal characteristics were compared with those of finite element analysis. When the pump was operated at a specific rpm, the natural mode whose resonance frequency is twice the rotating angular speed induced the large vibration. The retrofit utilizing stiffeners to reduce this resonant vibration were performed. Effects of designed stiffeners on reducing vibration were validated through tests after actual installation.

• Journal of the Korean Institute of Telematics and Electronics S
• /
• v.34S no.7
• /
• pp.89-101
• /
• 1997

A technical method of noise modeling and adaptive filtering reducing of speckle noise in ultrasonic medical images is presented. By adjusting the characteristics of the filer according to local statistics around each pixel of the image as moving windowing, it is possible to suppress noise sufficiently while preserve edge and other significant information required in diagnosis. Homogeneous factor(HF) from the noise models that enables the filter to recognize the local structures of the image is introduced, and an algorithm for determining the HF fitted to the diagnostic systems with various inner statistical properties is proposed. We show by the experimented that the performance of proposed method is superior to these of other filters and models in preserving small details and suppressing the noise at homogeneous region.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.957-963
• /
• 2008

The refrigerant-induced noise of the air conditioner is one of the irregular noises which occurs at the indoor unit. Because the air-conditioner makers are always trying to reduce the sound pressure level radiated from indoor unit, reducing the refrigerant-induced noise at low cooling mode is very important problem. But it is very difficult to estimate whether the refrigerant-induced noise occurs or not before it becomes problem. In this paper, a method to predict the refrigerant-induced noise is suggested using flow pattern map. It is estimated that the irregular noise from the refrigerant comes from the slug flow in a pipe.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.10a
• /
• pp.98-103
• /
• 1996

Elimination of squeal noise generated during brake application is an important task for the improvement of comforts in vehicles. In this paper, the structure of the wet brake and its operation are described first, and the cause of the noise is analyzed by identifying how the factors such as torque, speed, oil pressure, lubricant, and friction material affect the noise. To verify the mechanism of generation of the noise, several experiments of brake applications are executed, Based upon the review on the technical papers and the results from the experiments, several solutions to reduce the noise, available in real applications, are suggested, and the feasibilities of them are confirmed through the applications to the current system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.11a
• /
• pp.550-553
• /
• 2004

Recently, the demand for the Floating, Production, Storage, and Offloading facility (FPSO) which has some economic and technical advantages, has increased in offshore oil production areas. The 36,8000 DWT class FPSO was built in Hyundai Heavy Industries and will be installed in Offshore Angola. She dose not have self-propulsion system, but has additional facilities for oil production and positioning system. Main noise sources are contributing to the cabin noise of the accommodation are classified into three classes such as the machinery in the engine room and the deckhouse, HVAC system, and the topside equipments. In general, the noise regulation for the offshore structure is severer than that of the cargo ship and acceptable noise limit of cabin is specified as 45 dB(A). This paper describes the procedure of noise analysis, the countermeasures of noise control, and the measurement results of the quay trial. In order to minimize the noise levels, careful attention have to be paid by the special committee of experts from the initial design stage to the delivery. Proper countermeasures, considering the characteristics of sources and receiver spaces, were applied from the noise prediction and various experiment results. Finally, this ship was successfully delivered with excellent noise properties. The technology to minimize the noise levels for FPSO has been established throughout the construction of this ship.

• Proceedings of the KIEE Conference
• /
• 1996.07a
• /
• pp.406-408
• /
• 1996

This paper describes the BLDC motor which is applicated for a top front loading domestic washing machine. This motor is adopted direct drive washing machine without gear-belt-pulley system. Because gear box is removed, machine volume and noise are reduced. Moreover mechanical troubles in gear box are removed. Realization of variable speed region through of PWM control and high speed is able to efficient washing and spinning.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2020.07a
• /
• pp.17-18
• /
• 2020

본 논문에서는 산업 현장에서 사용되는 기계들의 이상을 감지하고 잔존수명을 예측하는데 사용되는 중요한 지표 중 하나인 체인의 신율을 측정된 소음을 통해 계산하려고 한다. 본 연구에서는 Edge에서 측정한 소음데이터를 기반으로 스텝 체인의 특성을 고려하여 소음데이터의 파형을 분석하여 체인으로부터 발생되는 특징을 감지하고 해당 특징을 이용하여 대역통과필터와 최소분산을 이용하여 스텝 체인의 신율을 측정한다.

• Safety and Health at Work
• /
• v.8 no.2
• /
• pp.226-230
• /
• 2017

The performance of sound barriers was evaluated to determine their technical effectiveness and practicality in reducing noise exposures to operating engineers in construction. Commercially purchased sound dampening mats (SDMats) were installed inside three heavy-equipment engine compartments. Sound pressure levels (SPLs) were measured before and after installing the SDMats while the equipment was on idle and full-throttle settings where it normally operates. SPLs inside the heavy-equipment operator cabs were significantly reduced by 5.6-7.6 dBA on the full-throttle setting following installation of the SDMats (p < 0.01). The evaluated engineering control intervention was simple to install, affordable, and substantially reduced the engine noise reaching the heavy-equipment operator, potentially reducing reliance on hearing-protection devices to protect construction workers from noise exposures.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.979-981
• /
• 2006

Recently as the well-being diffuse and the living standard improves. People's demand for an environment lifestyle is gradually on the rise. The major source of the subway running train is rolling noise generated by the surface condition of wheel and rail. In this study, we research trends on the reduction noise level. Further-more, special traffic Ubiquitous helps to environment technical development.

• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.291-294
• /
• 2000

Analysis of the contribution of each pass-by noise source to the overall pass-by noise is an important issue for reduction of pass-by noise. A technical approach for predicting tailpipe noise is used to identify the contribution of tailpipe noise to the pass-by noise in this study. Simulation program with a time domain engine modeling program called 'WAVE' and wave propagation theory of moving noise source are employed. Since the Doppler phenomenon causes a frequency shift during a pass-by noise test, the Doppler correction and time delay effects are incorporated into the estimation of tailpipe noise. The developed program can furnish an in-depth understanding of the effect of tailpipe to pass-by noise.