• Fire Science and Engineering
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• v.23 no.5
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• pp.153-160
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• 2009

This study aims to review the propagation characteristics of fire alarm sound in building through computer simulation. In order to achieve this goal, the sound power level of existing three different emergency alarms were measured in an anechoic chamber. Sound power level of alarm bell was 98.6dB and electronic-siren speaker was 95.7dB, and electronic-siren phon was 101.8dB at the voltage of DC 24V in the condition of anechoic chamber. As the results of acoustic simulation, it was shown that sound levels at the corridor of the building were relatively high and even. But, there were large difference in sound level at all the frequency bands between corridor and lecture rooms. This mean that alarm sound couldn't be recognized sometimes in lecture rooms. Through the computer simulation, the propagation characteristics of fire alarm sound could be forecasted and compared due to plans of buildings.

• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.713-722
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• 2022

In this paper, the flow performance and aero-acoustic noise generated by the target centrifugal fan system were investigated numerically and experimentally. Also, the numerical method for Computational Aero-Acoustics were evaluated by comparing each method. To analyze the performance of the centrifugal fan experimentally, the acoustic power level was measured in the semi-anechoic chamber using microphones, and the active frequency range for the noise performance was identified and that frequency range was applied for Computational Aero-Acoustics (CAA) techniques as sampling frequency. Then, Navier-Stokes equation and the Ffowcs Williams&Hawking equations were used to analyze the flow and sound power numerically, respectively, and a virtual acoustic radiation plane was designed and used for the implementation of the sound field. The accuracy and numerical characteristics of the numerical methods were validated by comparing simulated acoustic power levels with acoustic power levels measured.

• Journal of the Korean Society for Railway
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• v.14 no.3
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• pp.211-215
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• 2011

Generally, sound power is one of the most significant factors to predict and assess noise from sound sources. However, many researchers developed indirect methods to calculate the sound power with noise level because it is impossible to measure sound power directly while a train is running. In this paper, we propose a method to estimate sound power generated due to wheel/rail interaction and propulsive equipment from the measurement of noise emitted from rolling stocks and verify the estimation method by comparing with the other sound power estimation formula. We also analyze the sound power of rolling stocks which are operating in domestic lines such as EMU, Mukoonghwa, KTX using the method proposed in this paper.

• The Journal of the Acoustical Society of Korea
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• v.39 no.2
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• pp.105-112
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• 2020

An analysis model of noise map is proposed to evaluate and reduce the acoustical noise of power plant and its surroundings. The sound powers of many noise sources are estimated by measuring the sound levels of major equipments in the power plant. The analysis of noise has been made by using ENPro that is a commercial program for environmental noise prediction. The proposed model is verified by comparing the results from noise analysis and measurement at several points of the power plant units 1 through 4, and residential areas. It is shown that noise map simulation using the proposed model has a reliability, since the overall noise level approximates within the error of ±2 dB. Furthermore, through noise analysis, the increasing effect of noise due to newly established units 5 and 6 on residential areas is also analyzed. Consequently, the noise barrier is designed to meet an environmental noise standard and satisfy low cost and safety conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.104-109
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• 2002

The purpose of this study is to calculate transmission loss of KHST passenger vehicle's wall section accurately Typical transmission loss measurement of wall in the laboratory condition was carried out in advance, which is easier than KHST. Transmission loss results were compared with those by statistical acoustic method. Transmission loss values of KHST calculated by experimental method are compared with those from closed form solution.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.827-828
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• 2012

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.240-241
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.246-252
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• 1996

본 연구는 아음속 충돌분류의 소음특성에 관한 연구로서 분류가 매끄러운 판(smooth plate)에 충돌 할 때 발생하는 충돌소음의 음압레벨, 지향성 그리고 음향파워 등을 구하기 위한 것이다. 연구방법은 Fig.1에서와 같이 노즐지름 d와 노즐과 평판과의 거리를 h라 할 때 노즐상류측에 있는 서지 탱크(surge tank)의 압력이 1.0atg에 도달한 상태에서 단계적으로 강하시키면서 h/d에 따른 충돌소음의 레벨을 측정하였다. 또한 탱크압력을 일정하게 유지시킨 상태에서 충돌소음의 지향성을 측정하고 음향파워를 계산하였다. 자유분류인 경우에도 같은 방법으로 측정하여 충돌음의 경우와 비교 고찰하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.6 s.99
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• pp.635-644
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• 2005

This paper is. a study on relation between road traffic noise(RTN) and sound power level(PWL). At present, many experimental formulae and prediction formulae are used for prediction of RTN. But these formulae are difficult to appiy to the metropolitan area because these formulae are inaccurate in the different condition from reference condition. This paper calculate RTN and PWL of each prediction formula, choose the best one and make a noise map of the subject area. Procedure is as follows. First, calculate $L_{eq}$ of RTN using experimental formulae and prediction formulae. Second, calculate PWL using $L_{eq}$ of RTN and distance attenuation for point source at semi-free field. Third, choose the most accurate formula. And finally, make a noise map of the subject area at present and future. The result using noise map will be able to apply to application field. Noise mapping tool used on this paper is Raynoise program using Ray Tracing Method(RTM), Mirror Image Source Method(MISM) and Hybrid Method(HM).

• Journal of Korean Society of Environmental Engineers
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• v.34 no.4
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• pp.232-238
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• 2012

In this study, the noise mapping simulation is executed to design an effective barrier reducing noise levels of a school site. The geographical features of the ambient site and the school buildings are modelled in detail in order to consider sound propagation, deflection, and absorption phenomena etc. The main sound source, sound power level of expressway, is estimated on the basis of measured noise levels at several points of the site. The noise mapping simulation is performed by using ENPro, environmental noise prediction program based on ISO 9613 to analysis the effectiveness of noise barrier. Consequently, the noise barrier is designed to meet an environmental noise standard and satisfy low cost and safety conditions.