• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.170-175
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• 2000

Vibration and vibration-induced noise, major sources of occupant complaint, are increasing in modern buildings, Lighter weight construction and equipment located in penthouses or intermediate level mechanical rooms increase structure-bone vibration and noise transmission. In this paper discusses about testing vibration isolation systems and about the effectness of floor flexibility for vibration transmission.

• The KSFM Journal of Fluid Machinery
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• v.3 no.3 s.8
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• pp.31-40
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• 2000

A computer program is developed for the prediction of the aerodynamic performance and the noise characteristics in the basic design step of axial flow fan. The flow field and the performance of fan are analyzed by using the streamline curvature computing scheme with total pressure loss and flow deviation models. Fan noise is assumed to be generated due to the pressure fluctuations induced by wake vortices of fan blades and to radiate via dipole distribution. The vortex-induced fluctuating pressure on blade surface is calculated by combining thin airfoil theory and the predicted flow field data. The predicted performances, sound pressure level and noise directivity patterns of fan by the present method are favorably compared with the test data of actual fan. Furthermore, the present method is shown to be very useful in optimizing design variables of fan with high efficiency and low noise level.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.6
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• pp.591-598
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• 1984

The results of measurements showing normal vibrations and rubbing noise generated during unlubricated smooth sliding between metal surfaces are presented. The measurements were made on pin-on-disc type apparatus instrumented with piezoelectric acceleration transducers and microphones. Spectral analysis of the both signals up to frequency of 10kHz indicates that they are closely correlated. The major components of both signals in this frequency range are primarily associated with the normal contact vibrations which are excited by surface irregularities being swept through the contact region during sliding. As an approximation to the seismic input of surface irregularities, an effective surface wavenumber spectrum was assumed in the form of an inverse vibration and noise measurements for a number of surface finishes and mean loads. The predominant frequency component of which levels of the normal vibration and noise are close to overall levels of the both signals is induced by contact resonance between the two bodies and its frequency can be calculated from the Hertzian theory.

• Korean Journal of Optics and Photonics
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• v.18 no.1
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• pp.44-49
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• 2007

We have transferred a narrow-linewidth $1.5{\mu}m$ laser beam through a 525 m fiber network with excellent transfer stability. The fiber-induced optical phase noise during the fiber transmission is cancelled by configuring a noise-canceling servo. The transfer instability was $2{\times}10^{-17}$ at 1 s of averaging time. We quantitatively analyzed the transferred optical frequency in the frequency domain and in the time domain.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.5
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• pp.30-41
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• 2017

Types of noise barrier installed for noise attenuation are largely divided into noise-absorbing format and noise-proofing format. In these days, installation of transparent noise barrier is general trend to solve problems that hinder sunshine and landscape. Some kinds of transparent boards are used to one of components in noise barriers, but in some cases, less transparency and worse pollution due to yellowing phenomena, and severe material deformation are to harm the urban aesthetics Therefore laminated-tempered glass board in that yellowing phenomena does not occur can be replaced as a transparent one to secure those shortcomings. In this paper, the structural safety against train induced vibration and the resistibility to wind load are analyzed for laminated-tempered glass system as a component of noise barrier installed on Metro railway elevated bridges. Also the appropriateness is evaluated through flexural bending performance test, compressive strength test, modulus of elasticity tests, and impact test for the system or the glass material itself. All of these processes are intended to present the deployment of logic to evaluate the adequacy for the system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.8
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• pp.736-741
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• 2012

Squeak noise is studied by using the pin-on-disk system with aluminum pin and steel disk. Noise induced by friction is measured with respect to the normal loads and sliding speeds. The negative slope of friction-velocity curve is seen when the squeak noise occurs. It is found that the normal load influences on the sound level of squeak noise. From the hammering test, the major frequency of the squeak noise is shown to correspond to one of system modes, which implies that squeak phenomenon arises from the unstable system modes. The result of FE analysis shows that the major squeak mode is the bending mode of the pin.

• Journal of Environmental Science International
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• v.8 no.4
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• pp.457-464
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• 1999

To develop managing guidance of occupational noise exposure for metal working facility, we have studied about drafting contour map of noise exposure, methods of noise assessment and actual calculation method of time weighted noise exposure. Therefore we have suggested that contour maps of noisy workplace are very important for controlling metal working fluid facility and two kinds of noise assessment method, so called, personal andstatic exposure are necessary to avoid argument between workers and managing group. Finally we would like recommend that the Korean specification of noise exposure should be modified to protect ONIHL(oocupational noise induced hearing loss).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.4
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• pp.332-338
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• 2014

Experimental study is conducted for investigating the characteristics of friction-induced noise with respect to the variation of system geometry. In this study, a vertically fixed rod is in contact with the reciprocating plate which is controlled by the step motor. Friction noise is generated during the reciprocating motion due to the frictional contact between the plastic pin and the aluminum plate. The frequencies of the friction noise are changed when the height of the rod varies. However, it is found that the vibration modes involved in the friction noise are not changed. It implies that the unstable modes remain unstable regardless of the change of the system geometry, and thus, there are the certain mode shapes which are likely to produce friction noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.403-407
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• 2009

It is reported that the heavy weight floor impact noise of a slab system is very sensitive to the location of microphone and impact load. In addition, it is known that the aspect raio, thickness and boundary condition of a slab also have great effect on the noise induced by impact load. However, the effect has been mainly evaluated by experimental test and numerical analysis is nearly performed to verify the effect quantitatively. In this study, the effect of the aspect ratio, thickness and boundary condition on the heavy weight floor impact noise is examined through numerical analysis for simple rectangular slab system. The results show that the thickness and boundary condition have a strong correlation with the noise of the slab, on the contrary, the aspect ratio has little relation with the noise.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.629-634
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• 2001

The construction of the elevated railway has led to concerns about the noise from trains, particularly as tracks often pass close to residential dwellings. One specific issue relates to the noise from trains on bridges. The wayside noise for the train was measured to get the basic data that can be used to prepare count measures for solving environmental noise problems. Noise levels were measured simultaneously at three points in various distances from the railroad and at four points classified by floor. In this paper we measure the wayside noise in elevated railway and noise of normal operation compare with operating under train engine idling condition and investigate effect of nearby-building induced by train operation.