• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.848-853
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• 2005

The objective of this paper is to address to the providing an adequate noise and vibration solution, required for High Speed Rail while maintaining the stability criteria of the ChonAn station structure, the first constructed in Korean High Speed Railway. The significant acoustic pressure level will be induced by the high speed trains passing-by. Therefore, the high level study of this case is necessary. The acoustic pressure level of 85 dB(A) inside the ChonAn station is expected, and the spaces below concrete slab are not suitable for commercial purpose, thus installation of filtering systems (spring boxes containing viscous dampers, ballast mats and acoustic shield) are provided to reduce the effect of the noise and vibration to acceptable level of 55 dB(A). But, a major drawback of application of the previously conducted experimental results was that the actual effect of installation of filtering system was never been validated. Therefore, the acquisition of noise and vibration on the present structure were obtained and compared to the computer simulations. These predicted the behavior of the station reasonably well. Also, the installation of filtering systems gave the superior reduction on noise and vibration. This application is successfully adapted without scarifying stability criteria related to the structural stability including excessive deformations or displacements. Three traffic operation safety limits: deck vertical acceleration, deflection of the structure, and longitudinal displacement of the slab were satisfactory.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.307-310
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• 2000

Recently, the demand for the Floating, Production Storage, and Offloading facility(FPSO) which has some economic and technical advantages, has increased in offshore oil production areas. The basic characteristics of a 343,000 DWT class FPSO which is being built in Hyundai Heavy Industries and shall be installed in offshore Angola, is almost same as that of oil carriers. However, she do not have self-propulsion system, but has additional facilities for oil production and positioning system. Main noise source contributing to the cabin noise of the accommodation, are classified into the machine in the engine room and the deckhouse, HVAC system, and the topside equipments. In general, the noise regulation for the offshore structure is much severer than that of the common commercial ships and the maximum acceptable sound pressure level of cabins is specified in 45dB(A). This paper describes the procedure of noise analysis along with its results. Noise analysis has been carried out for the case of emergency diesel generator running condition and the case of normal production condition and the results has been compared with the measurement results of the first case. Based on the results, proper countermeasures to reduce excessive noise level has been applied considering the characteristics of sources and receiver spaces and can be satisfied the specifications at all spaces.

• 한국군사과학기술학회지
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• 제5권4호
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• pp.27-37
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• 2002

Airborne noise is one of the considerable environmental factors for navy ship personnel because of accomplishing their tasks on restricted ship spaces. In this study, the effects of airborne noise on personnel and existing criteria for acceptable airborne noise on ships are reviewed briefly. Statistic results of airborne noise levels of the Korean navy ships are analyzed according to the class of ships and are compared airborne noise levels of the US navy ships. These results can be used for proposing airborne noise criteria of the navy ship for the future.

• 음성과학
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• 제11권1호
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• pp.43-52
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• 2004

This paper concerns an effective dual-channel noise reduction method to increase the performance of speech recognition in a car environment. While various single channel methods have already been developed and dual-channel methods have been studied somewhat, their effectiveness in real environments, such as in cars, has not yet been formally proven in terms of achieving acceptable performance level. Our aim is to remedy the low performance of the single and dual-channel noise reduction methods. This paper proposes an effective dual-channel noise reduction method based on a high-pass filter and front-end processing of the eigendecomposition method. We experimented with a real multi-channel car database and compared the results with respect to the microphones arrangements. From the analysis and results, we show that the enhanced eigendecomposition method combined with high-pass filter indeed significantly improve the speech recognition performance under a dual-channel environment.

• 한국자동차공학회논문집
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• 제18권5호
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• pp.37-44
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• 2010

Impact noise is induced in a car when it is driven on a harsh road or over some bumps. This noise occurs with the very high level of sound, which affects passengers in some way or other. Although it is impossible to clearly remove such noise, it is necessary to research an improvement in sound quality for impact noise. A new sound metric for impact sound is presented. This metric is verified by comparison between mean subjective ratings and several sound metrics. In this paper, more objective attributes are considered, which the attributes are expressing the level and modulation of sound. Three sound metrics are employed to get impact sound indexes for each course by the method of multiple linear regressions. The indexes are verified by considering the correlation between the estimated values from the multiple linear regressions and the mean subjective ratings by evaluators. Also, the subjective ratings on the indexes are estimated for the case in which some parts of suspension system are changed. The estimated ratings represent more reasonable or acceptable ratings. Thus, such indexes can be used for modification of the parts of suspension system under considering a good sound quality.

• 소음진동
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• 제9권4호
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• pp.841-848
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• 1999

직류 모터의 생산 공정품질 확인 작업에 있어서 전체 소음레벨이 합격점에 이른다 할지라도 관능 평가시의 이음으로 인해 불량판정을 받게되는 경우가 있다. 이런 종류의 문제는 가공 또는 조립 공정상에서 발생될수 있는데 본 눈문에서는 과도기적 스펙트럴 분석 혹은 시간-주파수 분석 기법을 소음품질 문제에 적용해 보았다.Case Study로써 윈드쉴드 와이퍼 모터의 이음 발생원이 상세 분석되었으며, 결과적으로 정상적인 주파수 분석에서 발견되지 않았던 아마추어 축의 불량이 충격소음을 일으킨것으로 밝혀졌다. 이를 통해 회전체-기어 시스템의 이음 원인규명을 위한 시간-주파수 분석 기법의 효과적 활용이 잘 나타났다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.125-129
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• 2003

The identification of location and strength distribution of extended noise sources is important in the practical noise control engineering, especially in the viewpoint of dealing with the inherent nature of noise problem in question. For noise source ranking inside an automotive vehicle, the window method has been mainly used due to its simplicity. However, time and cost drawbacks in the measurement and inaccuracy due to low-frequency tunneling and lack of phase information have been a serious problem in using this method. In this study, the inverse FRF method was employed to carry out the noise source ranking inside an automotive vehicle and it was also used to predict the interior sound pressure with the change of sound insulation materials. As a result, it was found that the source contribution of vehicle panels could be successfully identified in comparison with the window method. The sound pressure at driver's ear position was predicted based on the obtained data and was compared with the measured data. The agreement in spectral trends was acceptable and their difference in level was within 3㏈ above 500㎐.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 E
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• pp.1592-1595
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• 1998

The rock fragmentation system with a capacitor bank, switching device, cable and blasting electrode are described. Utilization of the chemical energy from the electrolyte and the pseudospark with a large current capacity suggested the commercialization possibility of the rock fragmentation system. The vibration and noise level of the pulsed blasting is acceptable in the most ground breaking. And also the electromagnetic force produced by the inductor is introduced for the rock fragmentation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.137-142
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• 2009

Impact noise is induced in a car when it is driven on a harsh road or over some bumps. This noise occurs with the very high level of sound, which affects passengers in some way or other. Although it is impossible to clearly remove such noise. It is necessary to research an improvement in sound quality for impact noise. A new sound metric for impact sound is presented in the previous work. This metric is verified by comparison between mean subjective ratings and several sound metrics. In this paper, more objective attributes are considered, which are the attributes expressing the level and modulation of sound. Three sound metrics are employed to get impact sound indexes for each course by the method of multiple linear regressions. The indexes are verified by considering the correlation between the estimated values from the multiple linear regressions and the mean subjective ratings by evaluators. Also, the subjective ratings on the indexes are estimated for the case in which some parts of suspension system are changed. The estimated ratings represent more reasonable or acceptable ratings. Thus, such indexes can be used for modification of the parts of suspension system under considering a good sound quality.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.74-79
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• 2002

The piping verification tests were performed in order to verify the structural integrity during initial operation of the reactor coolant systems and the primary heat transportation systems of nuclear power plants by KEPRI in Korea. The tests were conducted at full operating temperature and pressure. The objective is to evaluate the possibility of excessive load generating on piping, piping supports, and reactor structures etc. in the steady normal operation and expected pump transient conditions. As a result, the measured vibrations have been shown acceptable level according to ASME/ANSI OMa-Standard, Part 3.