• Journal of Korean Association for Spatial Structures
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• v.9 no.3
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• pp.59-66
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• 2009

Dynamic characteristics such as frequency and damping ratio in the ambient state of building has been progressed in domestic and foreign. However, there has not been any deep research of dynamic characteristics of full-scale structure using vibration measurement of the building damaged up to failure. Dynamic characteristics of three-story reinforced concrete building was evaluated before and after it was damaged by using a actuator. Dynamic characteristics is reviewed and compared with previous study. Ambient vibration and human excitation test were applied. After 120mm horizontal displacement by actuator, frequency of long and short direction is reduced to 34.3%, 33.7% and damping ratio is reduced to 36.5%, 19.5% respectively.

• Journal of Sensor Science and Technology
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• v.16 no.3
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• pp.165-173
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• 2007

A differential floating mass transducer has been developed in Korea for fully implantable middle ear hearing devices (F-IMEHDs). In particular, the performance of a differential floating mass transducer (DFMT) is very important among the parts of the F-IMEHDs because the mechanical vibration generated by DFMT is delivered to the inner ear directly. In this paper, the electrical model is proposed to analyze the DFMT vibration characteristic using the mechanical model of the DFMT. The electrical model enables the simple analysis of DFMT vibration characteristics using a computer program. The proposed electrical model is simulated through PSpice as changing the values of passive elements in the electrical model. To verify the proposed model, the DFMT has been implemented on the basis of the simulated results and the experiment for vibration measurement has been carried out. Through the comparison, it is verified that the proposed model is useful to analyze the vibration characteristics of the DFMT.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.999-1003
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• 1992

Because of low noise and small size with huge capacity, a centrifugal fan is widely used for ventilation, air-conditioner and so on, which are very near to human life. Because of the complexity of its vibration and noise generation mechanics, most of researches on them are based on experimental methods. This study is to characterize the centrifugal fan noise and vibration. It is considered that noise is composed of the structural vibration noise and the air flow induced aerodynamic noise. To decouple the structural vibration noise the centrifugal fan is masked with an adhesive tape, such that air blowing is prohibited thus only the structural vibration noise is extracted. The noise level and characteristics in the frequency domain are verified and compared with those of total mixed one. This study shows some significant results that the structural vibration noise has relatively narrow band power spectrum compared with the total mixed one and has a strong periodicity. The sound level is lowered about 5dB by the removal of air flow with the masked fan for an air-conditioner used in this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.205-209
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• 2007

During after the Industrial Revolution until now, as many of working machinery and tool had been invented, human could save man power and time. However, because such instruments generate a loud noise according to their use-purposes and dimensions, they are affecting a physical, mental bad influences to those workers. Therefore, while a reduction measure against the instrument-noise that generates at workshop is sincerely necessitated, due to lack of the research and data concerned with that, a lot of difficulties are on suffering. Standing on such point of view, this Study has measured analyzed the characteristics of diverse instrument-noises generate at workplace, and would intends to present a fundamental material for establishment more comfortable working environment by prediction on the noise in loud noise workshop, based on the above.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1183-1186
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• 2007

The low frequency noise, including infra-sound is known to affect human physiology and psychology. Guidelines and measurement method of low frequency noise has been introduced in several countries in order to evaluate low frequency noise. In this work, low frequency noise characteristics of dump truck was investigated in terms of the noise level and spectrum. The interior sound pressure level of the dump truck was between 60 and 105 dB in the frequency range of $1{\sim}250$ Hz.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.707-711
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• 2004

Recently, the interests about noises have increased with the rapid development of our living environment Until now the estimation methods to sounds have used the equivalent levels. The sensitivities of human beings aren't considered in these methods. It's a situation to need new estimation methods for environmental noises. They must be analyzed by the characteristics of sounds before making the noise regulations newly. In this study, the noises were measured around our living environment And the frequency analysis, Sound Quality Metrics, the cluster analysis and so on are used to classify the environmental noises.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.586-591
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• 2002

Recently, the research and discussion to set up the evaluation standard for nor impact noises in multistory residential buildings has been vividly carried out In Korea. Therefore, the correlation between the methods and auditory responses was investigated through this research to investigate the applicability of the L index evaluation method and the reverse A characteristics evaluation method that are listed in JIS A 1419 since Japanese circumstance are similar to Korean after evaluating the duality of Korean multistory residential buildings. As a result, it was found that the correlation between the value resulted from L index evaluation and the value from reverse A characteristics evaluation is high. In addition, it was also revealed that human responses to each Impacter was similar. Consequently, it is considered th:31 the tendency about the two methods would be similar.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.725-730
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• 2012

In this paper, flow noise characteristics of Savonius-type vertical-axis wind turbines are numerically investigated using hybrid CAA techniques. High frequency harmonics as well as BPF components are identified in the predicted noise spectra from a Savonius wind turbine. As the BPF components belong to infrasound, the higher harmonic components affects human response dominantly. Further analysis is performed to investigate the reason causing the higher frequency harmonic noise by changing operational conditions of a Savonius wind turbine. Based on this result, it is revealed that the frequency of higher harmonic components is determined by the radius of blades and angular velocity of Savonius wind turbine.

• Tunnel and Underground Space
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• v.2 no.1
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• pp.102-115
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• 1992

Blasting operations associated with rock excavation work may have an environmental impact in nearby structures or human beings. With the increase of construction work in urban areas, vibration problems and complaints have also increased. In order to determine the optimum design parameters for safe blast, it is essential to understand blast mechanism, design variables involved in blast-induced damage, and their effects on the blasting results. This paper deals with the characteristics of ground vibrations, air blast and fly rock caused by blast, including the general method of establishing the vibration predictors, and damage criteria suggested by various investigators. The results of field measurements from open pit mine and tunnel construction work are discussed. Basic concepts of how to design blast parameters to control the generation of ground vibrations, air blast and fly rock are presented.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.5
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• pp.469-483
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• 2012

The propagation characteristics of a mechanical wave in human soft tissue depend on its elastic properties. Investigation of these propagation characteristics is of paramount importance because it may enable us to diagnose cancer or tumor from the vibration response of the tissue. This paper investigates and compares displacement patterns generated in soft tissue due to several forms of low-frequency vibration sources placed on a surface. Among vibration sources considered are a normal load, tangential load, and antiplane shear load. We derive analytical expressions for displacements in viscoelastic single layers, and calculate displacement patterns in half space and infinite plate type tissue. Also, we simulate the vibration response of a finite-sized tissue using finite element method. The effects of the type of stress, the size and frequency of vibration sources, and medium boundaries on displacement patterns are discussed.