• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.1
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• pp.87-93
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• 2008

Seismic control performance of MR dampers, which have severe nonlinearity, varies with respect to the dynamic characteristics of an earthquake such as magnitude, frequency and duration. In this study, the effects of excitation characteristics on the equivalent linear system of a building structure with the MR damper are investigated through numerical analysis for artificial ground motions generated from different response spectrums. The equivalent damping ratio of the structure with the MR damper is calculated using Newmark and Hall's equations for ground motion amplification factors. It is found that the equivalent damping ratio of the structure with the MR damper is dependent on the ratio of the maximum friction force of the MR damper over excitation magnitude. Frequency contents of the earthquake ground motion affects the equivalent damping ratio of long-period structures considerably. Also, additional damping effect caused by interaction between the viscousity and friction of the MR damper is observed. Finally. response reduction factors for equivalent linear systems are proposed in order to improve accuracy in the prediction of the actual nonlinear response.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.754-758
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• 2006

The purpose of this study is to propose calculation and application method of a common factor from different noise source unit such as $L_{eq}$ and WECPNL, A calculation was conducted by method that propose TNO-PG. Also, An applied example is a noise environmental standard of Korea and Japan. After %HA of two country are calculated, noise standards of two countries were compared by using %HA. The result by a equation of %HA is to convert a noise level($L_{dn}$) into a %HA. To calculate a %HA, First $L_{eq}$ is converted into $L_{dn}$. Then, $L_{dn}$, has inputted into and %HA has deduced from a %HA equation of TNO-PG. If the same area is applied the same %HA value according to area categories, it can be applied the same %HA to different noise sources. As a results. a noise levels have computed different values because responses of human change in accordance with a noise sources. This results can be applied to the noise environmental assessment for a domestic railway and aircraft noise.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.1087-1092
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• 2006

Recently, traffic noise level is rapidly increasing, and it is crowed caused by recently overcrowded and overgrown cities, and increasing traffic volume is emerging as a major factor of disrupting the living and working environment. In this situation, citizens are increasingly complaining about the traffic noise. The noise level of in major cities in Korea is serious and affects on citizens physically and psychologically. Many people live in residential areas around crowed roads in major cities, such as Seoul. Accordingly, the purpose of this study is to predict outside noise distribution of building through survey and simulation to make better sound insulation performance research. The result of this study shows that the traffic noise is influenced from ground 50m and analyzed that form of building and arrangement type must be considered to the level of noise decrease.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.975-982
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• 2004

Helmholtz resonator is used to reduce noise of the narrow frequency band. It has high transmission loss at its resonance frequency. The silencer that combines many resonators could control broadband noise at low frequency. To convey this rather simple idea, serial and parallel arrangement of resonators have been tested to obtain high transmission loss characteristics in the band of which are selects. Theoretical and experimental results explain these characteristics in the absence of mean flow. The change of acoustic characteristics by the resonance frequencies and resonators arrangement are explained by using the equivalent Impedance analysis that is defined in this paper. It shows that the transmission loss has a maximum value when the separation distance between each resonator is λ/4 of its wavelength.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.377-378
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• 2017

대용량 전력변환기는 가청주파수에 해당하는 낮은 주파수 스위칭 동작으로 전력변환기 구동 시 리액터 소음에 의한 공해를 유발하고 있다. 이러한 리액터 소음공해 제거하기위해 대용량 전력변환기의 높은 주파수 전압을 리액터에 인가할 수 있는 새로운 DC/DC 컨버터 토포로지를 제안한다. 본 논문에서 제안된 토포로지는 다수의 스위치를 병렬로 연결하여 스위치 인터리브 방식에 의한 높은 등가 스위칭 동작 구현이 가능하다. 따라서 제안된 스위치 인터리브 방식은 대용량 전력변환기의 리액터 소음을 제거할 수 있을 뿐만 아니라 리액터용 용량을 저감하여 전력변환기의 에너지 밀도 증대와 단가 감수 측면에서 큰 장점을 갖고 있다.

• Journal of KSNVE
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• v.6 no.3
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• pp.349-355
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• 1996

For a rail traffic noise, a typical source has a length of 200m - 400m so that the noise pollution areas have been located in the transition regions where the sound level drops between 3dB/dd and 6dB/dd. Therefore, in this region, parameters such as a horizontal distance from the track, the geometry of the ground surface, the environmental effect, and the boundary impedance condition play import roles, especially in our nation's situation. In this study, modelling techniques for the finite length of noise source have been investigated in order to evaluate the rail traffic noise level. Then. noise correction value .${\Delta}$SPL for various location in the track region is represented by the non-dimensionalized horizontal and parallel distance from the track. As an application, a high speed train is examined. Beas on the noise data measured for a Eurostar in France, the sound power value per unit length $H_1$is calcuated. It turns out that$H_1$is 109 dB. Overall sound power from the highspeed train to be serviced in our country is expected to 135 dBA.

• Progress in Medical Physics
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• v.11 no.1
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• pp.19-27
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• 2000

In order to predict the propagation of road traffic noise over level terrain, this paper presents the model of the simple monopole and dipole source. Excess attenuations by ground acoustic impedance with continuity are investigated by outdoor experiments. In this results, the propagation of road traffic noise is affected by the acoustic impedance properties of the ground surface over which the noise travels, particularly when the receiver position is close to the surface. These results are then used to derive sound pressure level contours for the attenuation with distance of the equivalent energy level received from passing vehicle. The percentage of deep sleep and the number of wakings are studied for continuous traffic noise. The hearing loss and sensitivity threshold shift is investigated by changing the various parameters such as the effects of aging and noise exposure. Evaluation of the response of human to traffic noise is discribed. It is shown that exposure to excessive noise can cause temporary loss of hearing that may become permanent if the exposure is prolonged or intense.

• The Journal of the Acoustical Society of Korea
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• v.25 no.3
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• pp.129-136
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• 2006

For the environmental noise assessments. A weighted equivalent noise level (LeqA) is used to measure the time varying environmental noise. However, it is not appropriately reflect various environmental noise features and human emotions. The human perception of the noise is affected largely by the psychoacoustic characteristics of noise as well as the sound pressure level In this study, the effective factors of noise qualify are analyzed using the subjective assessment and statistical analysis of environmental noise, such as road traffic noise. construction site noise, noise in daily living. and other. The analysis methodology is composed to three steps as follows : firstly, the values of the sound qualify metrics of various noise sources were analyzed. And to classify the noise sources, we conducted a cluster analysis using sound quality metrics. Secondly, subjective jury testing was carried out using the methods of paired comparisons and semantic differential. Finally, the correlation between the subjective parameters and the noise quality metrics were analyzed. As a result. the human perception characteristics of the various environmental noise are described in some physical parameters of the noise qualify metrics.

• The Journal of the Acoustical Society of Korea
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• v.26 no.7
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• pp.353-360
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• 2007

Rapid urbanization and population increasing are making a high-rise residential building and high-density residential area. According to spacial concentration of population is occurred road traffic noise problem. Now we are popularly using almost only noise barrier installation, but it makes many disfunctions such as poor landscape, low noise barrier performance and crimes. The purpose of this research is to figure out which is best method one the traffic noise management. Alternative are composed to building layout type ($30^{\circ},\;90^{\circ},\;180^{\circ}$), separation between road and residential building, noise barrier types(noise barrier only, noise barrier and forests and etc). The noise barrier are shown to reduce barrier and building layout angle $30^{\circ}$ position is the best comparing with horizontal and vertical layouts. The gab distance is decreased approximately noise level 5dB(A). We figured out there are noise important method except noise barrier wall and it was analyzed how much decreased. This can be very useful before making a road planning and residential building design.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.850-854
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• 2009

Approximate analysis for a building installed with a friction damper is revisited to get insight of its dynamic behavior. Energy balance equation is used to have a closed analytical form solution of dynamic magnification factor (DMF) for the building with combined viscous and friction damping. It is found out that DMF is dependent on friction force ratio and resonance frequency. Linear transfer function from input external force to output building displacement is obtained by simplifying DMF equation. Root mean square of building displacement is derived under earthquake-like random excitation. Finally, design of friction damper is proposed by processing target control ratio, damping ratio factor, and friction force in sequence.