• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.423-426
• /
• 2007

In this paper, vibration reduction of resiliently mounted machinery and effect of the foundation impedance is studied. SBN (Structure-borne noise) reduction through the mount is analyzed by assuming that the system is modeled as a mass-spring system, while the impedance of the floor is included in the prediction. The comparison of the SBN difference through the mount between predictions and measurements show that the slopes are similar in the case of single-mount system, while the measurements differs significantly from the predictions in the case of the double-resilient system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.239-243
• /
• 2006

A noise/vibration of the forklift happens in the driving axle to charge the drive and are examined closely by an each reason. After this study consider a reduction method of a noise/vibration about the gear, axle, bearing and others, the purpose of this study is to reduce a noise/vibration for a stability of the total system. From the data to be measured through all experimental method, the problems of the gear, axle, bearing, housing and others are examined closely, and the forklift is derived the model to be the engineering. The Mechanism of the problem occurrence is examined through a palametric research about an each influence factor. Lastly, the resuls of this study propose the model to he improved.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.10a
• /
• pp.687-692
• /
• 2011

Experimental analysis has been carried out on noise reduction of subsonic jet flow with chevron nozzle to investigate relationships between geometry variation of chevron nozzles and jet noise reduction. Including base nozzle, seven nozzles are tested at Mach number 0.9. Parametric variables are chevron count, chevron length, and chevron shape. From these experiment, the more chevron count increase, the more jet noise reduction gain. Varying the chevron length, short chevron nozzle increase the jet noise at certain direction all the more. Chevron shape is also considered as important factor to reduce the jet noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.212-216
• /
• 2006

The purpose of this study is to obtain an effective enclosing method for noise reduction of press machine operating in a manufacturing company located in Korea. Noise level of the machine is about $90{\sim}105dB$ which is higher than legal standards by industrial safety and health law. This study has predicted the level of noise reduction according to a step by step prevention plan by considering the characteristics of the cause of noise, the permitted limit of noise levels, problems and economical efficiency attendant upon the noise prevention measures. The predicted level of noise at the plant in accordance with the first step is $71.5{\sim}89.5dB(A)$, and can satisfy the permitted limit of noise in a time period of the day. Based on these results, enclosing method adequate for the selected plant's noise characteristics were suggested.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.49 no.1
• /
• pp.1-8
• /
• 2000

Switched reluctance motor(SRM) has simple magnetic structure, and requires simple power electronic driving circuit. It is very useful for wide range adjustable speed drive system. But, SRM drive generates large vibration and acoustic noise because it is commutated individually by step pulse m.m.f of each phase pole. In the vibration and acoustic noise characteristics. The considerable vibration and noise is induced by radial deforming of stator, so the frequency of dominant vibration and noise is coincident with the frequency of natural mode frequency of mechanical structure. This radial vibration force is generated in the phase commutation region. This paper suggests the new electromagnetic structure of SRM with auxiliary commutation winding which is excited by direct current. This phase and commutation winding are coupled magnetically between one phase winding and the other. Therefore, the switch-off phase current is absorbed by the another phase winding. By this interaction of phase and commutation winding in commutation mechanism, vibration and noise is reduced. And this reduction effect is examined by the test of prototype machine. As a result, SRM with DC exciting commutation winding is very useful to reduce vibration and acoustic noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.356-360
• /
• 2006

Recently, for the purpose of improving the isolation performance of impact noise, many resilient materials have been installed in a residential building. As one of the reduction method for improving the performance of light-weight impact noise, this study is focused on the load condition of floating layer over resilient material. We studied the correlation between the mass or load of the floating layer and the reduction of light-weight impact noise by experiments in reverberation chamber for testing the impact noise. The results show that the reduction of impact noise is improved by increasing the mass per unit area of floating layer until about $140kg/m^2$. But the reduction is not obvious by adding extra mass on the floating layer.

• 전기의세계
• /
• v.26 no.5
• /
• pp.74-82
• /
• 1977

This study is to present a method for reductin of noise and vibration of home electric motors coupled to the mechanical load causing relatively big amplitude of vibration. The noise and vibration factors have been analysed in the divisions such as the pattern related to the armature reaction, the pattern related to the circulating current by induction and the other patterns those are affected by a dditive magnetic field and have an effect on mechanical constants. From the systematic mutual relations between the patterns and daping effects, it is possible to derive the fundamental measure for reduction of noise and vibration. Vibration measurements and analysis were carried out in accordance with the planned experimentation and thre object model was chosen randomly from the production line in a factory where home electric machines were mass-produced. Based on the above-mentioned fundamental measure, suppression effects on noise and vibration have been analysed according to the number of slots, the amount of rotor skew and the way the stator winding connection was series or parallel.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.673-676
• /
• 2007

These days, the damage of noise has increased seriously by rapid change of life style because of the centralization of urban population, and the rapid increase of traffic. The Ministry of Environment has emphasis on the systematic management about the noise of daily life and the close connection of daily noise management policy with relevant ministries, and put into practice "the master plan of lessening the noise of daily life" from year 2006. This study tried to find out the reduction methods and the effective management of railway noise in the action plan of railway part of "the master plan of lessening the noise of daily life". According to this study, railway noise can be reduced greatly by taking action of railway detail plans. The cause of railway noise varies by rolling stock, track and more, so the reduction methods of railway noise can be studied specially, scientifically and constantly in every field.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.4
• /
• pp.439-447
• /
• 2008

One of the key elements in efforts to minimize noise radiation from a powertrain is the knowledge of the main radiating component and the relation between the surface vibration of a powertrain and the sound pressure. In this research, the powertrain model is developed based on FEM(finite element method). This model is applied to the prediction of the vibration of a powertrain by using ADAMS and the radiation noise by using BEM(boundary element method). According to this numerical analysis, the surface vibration of a powertrain is investigated as a source of radiated noise. This surface vibration is caused by the 1st order natural vibration of the cylinder block and its mode shape is the torsion mode. Therefore, this mode shape is modified to reduce the surface vibration of the powertrain. The radiation noise of the modified powertrain is also reduced to $5{\sim}12\;dB$. This modification is very successful for the noise reduction based on the CAE technology.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.11a
• /
• pp.570-573
• /
• 2004

Conventional methods for reducing vibration in engineering designs may be undesirable in conditions where size or weight must be minimized, or where complex vibration spectra exist. Some alloys with a combination of high damping capacity and good mechanical properties can provide attractive techanical and economical solutions to problems involving seismic, shock and vibration isolation. In this paper, it showed the noise and vibration characteristic was compared conventional rail joint to improved rail joint(damping alloy) for reducing noise and vibration. Its applicability to rail joint is discussed.