• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.634-637
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• 2007

A weighted sound pressure level has been used to evaluate sounds test or sound quality test for a refrigerator up to present but the customer had different satisfactions of refrigerator sounds with different listening position. It means that there was a sound directivity caused by a position of fan or compressor. In this paper, we proposed a sound power spectrum guideline that represents total sound of refrigerator.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.7
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• pp.693-698
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• 2009

Various acoustic tests were carried out to investigate the acoustic performance of diesel engine exhaust silencers. In order to consider flow effects, the test facility was set up composed of fan, duct and silencer. Using the test facility, insertion loss tests were carried out to improve the acoustic performance in the low-frequency ranges. Through a series of tests, it was found out that the array resonators having multi-perforated holes inside the exhaust silencer, might be very effective in the low frequency range. Consequently, the hybrid-type silencer which is the combination of reflective silencer with array resonators and conventional absorptive silencer, was proposed and its high performance in the low-frequency range was also verified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.25-28
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• 2008

This study investigates the effect of geometrical shape of concert halls, with variation in the shape and location of diffusers. The acoustical characteristics both in the audience area and on the stage 1:50 scale models of shoebox and fan-shaped halls. It was found that the front side walls affect sound diffusion. The 1:50 scale model based on the Boston Symphony Hall was used for monaural impulse response measurements for calculation of RT, EDT, C80, G and ST1. In addition, calculating the numbers and amplitudes of reflection rays were applied to quantify diffusion phenomena.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.111-116
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• 2003

In this paper, object of experiment is to study on the effect of cutting parameters to obtain optimal surface toughness in face turning. Surface roughness is significantly important to be high quality of parts produced by turning process. For this purpose, the optimization of cutting parameters for fan Owning operation is investigated applying the Taguchi method. An orthogonal array, signal-to-noise ratio, and the analysis of variance are employed to evaluate effect of cutting parameters fir face turning. Also confirmation tests were performed to make a comparison between the results predicted from the mentioned correlations and the theoretical results. Cutting experiment is performed without cutting fluid using coated tungsten carbide inserts about workpieces of SM45C.

• Journal of KSNVE
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• v.8 no.1
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• pp.122-131
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• 1998

Internal and external acoustic fields of the engine inlet are calculated by using a finite element method. The far fields non reflecting boundary condition is enforced by using a wave envelope element, which is a kind of infinite element. The geometry is assumed an axisymetric duct. Sources of the fan are modeled by the Tyler and Sofrin's theory. Effects of uniformly moving medium are considered. A pulsating sphere and an oscillating piston problem are calculated to verify the external problems, and compared with exact solutions. When the wave envelope element is applied at the far boundary, the calculated finite element solutions show good agreements with the exact solutions. The engine inlet is solved with the combined internal and external grid. The cut-off phenomena on engine inlet duct are observed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.831-836
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• 2004

Vibration of electric-powered hand grinder comes from the parts of motor, gear, bearing, and fan. Excessive vibration can be harmful to workers. To reduce vibration of a hand grinder we analyzed the frequency components from the routing electric-powered grinder and did modal test to find the natural frequencies of the each part. It shows that the vibration is due to the resonance of the case. To remove the resonance, the case structure is modified and the bearing cap is replaced on a basis of the results from the rotor dynamic analysis using SAMCEF. As a result the vibration of the hand grinder is reduced greatly.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.6
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• pp.486-494
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• 2004

This paper addresses the dynamic modeling and closed-loop eigenvibration analysis of composite rotating pretwisted fan blade modeled as non-uniform thin-walled beam with bi-convex cross-section fixed at the certain presetting angle and incorporating piezoelectric induced damping capabilities. The blade model incorporates non-classical features such as transverse shear, rotary inertia and includes the centrifugal and Coriolis force field. A velocity feedback control law relating the piezoelectiriccally induced transversal bending moment at the beam tip with the appropriately selected kinematical response quantity is used and the beneficial effects upon the closed loop eigenvibration of the blade are highlighted.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.1035-1040
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• 2004

The vibration of an electric hand grinder originates from the motor, gear, bearing, and fan. Its excessive vibration can be harmful to workers. To reduce the vibration of an electric hand grinder. frequency analysis for the vibration signals of a running electric hand grinder and modal test for the each part were done. The results show that the vibration is due to the resonance of the case. To remove the resonance, the case structure was modified and the bearing cap was replaced on a basis of the results of the rotor dynamic analysis using SAMCEF. As a result, the vibration of the electric hand grinder was reduced greatly.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1016-1019
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• 2002

This paper deals with a fundamental and classical scattering problem by a finite strip. For the analysis of scattered acoustic field, a “single” integral equation is derived. Firstly, the complexity by considering the effect of the mean flow is alleviated by the introduction of Prandtl-Glauert coordinate and the new dependent variable. Secondly, the difficulty of solving the resultant strongly-coupled integral equations which always appear in this kind of 3-part mixed boundary value problem is solved by observing some good properties of the functions in complex domain and manipulating the equations and variables for the use of those properties. The solution can be obtained asymptotically in terms of gamma function and Whittaker function. One aim of this study is the improvement of methodology for the research using integral equations. The other is the basic understanding of scattering by a finite strip related to the linear cascade model of rotating fan blades.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.245-246
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• 2014

에어컨의 실내기에서 발생하는 소음은 주로 회전하는 팬의 진동에 의하여 발생하게 된다. 이는 구조기인 소음으로 낮은 주파수특성을 갖고, 흡음이나 차음의 소음저감방법으로는 해결하기 어려운 특성을 가지고 있다. 본 연구에서는 벽걸이형 에어컨 원심팬에 발생하는 진동(sway motion)의 원인을 진동실험과 동역학 시뮬레이션을 통하여 규명하였다. 실험적인 측면으로는 시스템분석과 시그널분석을 통하여 원심팬 구성품의 물성치 및 동특성을 확보하였고, 해석적인측면으로는 실험으로 확보된 원심팬의 동특성을 바탕으로 동역학 시뮬레이션 모델을 수립하였다. 실험 및 동역학 시뮬레이션을 바탕으로 원심팬 진동의 원인을 규명하였고, 원심팬 진동의 원인은 원심팬과 모터축사이의 축정렬 불량임을 확인하였다. 이를 해결하고 진동을 저감하기위한 장치를 고안하고 실험을 통하여 진동저감효과를 확인하였다.