• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.7
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• pp.774-780
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• 2016

In this paper noise source and transfer path of tactical vehicle are analyzed with partial coherence function and spectrum analysis. Engine, transmission, structure panel and aerodynamic are main source of cabin noise. To reduce cabin noise, identifying transfer path of sources and analyzing their contribution is important. With modeling of transfer path and partial coherence function, transfer path and principal noise source can be identified. Engine/transmission and structural resonance are principal source of low frequency noise and by adding stiffener and sound absorbing material, resonance of vibration and inflow air problem can be solved.

• Journal of KSNVE
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• v.8 no.5
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• pp.862-869
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• 1998

The interior noise generated by the windshield wiper system including a wiper motor, the motor mountings and linkages is considered as a structure-borne noise. The structureborne noise is closely related with the system vibration which was transmitted into interior cabin through the car body. In this study, the frequency characteristics of vibration in the wiper motor system were first identified through the frequency analysis. Then effects of the wiper motor mountings and linkages on the vehicle interior noise were studied through in-vehicle measurements. Finally a possibility of noise reduction at a certain frequency was revealed from the study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.545-550
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• 1997

It is well known that Statistical Energy Analysis(SEA) is one of very attractive analytical methods to solve shipboard noise problems. With reasonable successes, many applications of SEA to shipboard noise prediction have been reported. However when one wishes to obtain theoretical predictions by using SEA in practical systems, he will find difficulty in modeling of source systems, that is, foundations where to place main engine, generator, compressor, and so on. Also, he will find that it is hard to determine the amount of power flow from machinery to structures. In this paper, SEA of a simple foundation model was carried out using the estimated amount of power flow from source; the estimated mobility method. The comparison between the estimated and measured results is presented. That comparison shows a method to get structure-borne noise power from the combination of machinery and foundation. This prediction method gave a good results for a air-compressor mounted on a model foundation. The method is expected to give a reasonable power output in practical problems.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.8
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• pp.155-161
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• 1999

아이들 상태에서 차실 내에 불쾌감을 주는 매우 높은 크기의 소음이 발생하였다. 본 논문에서는 아이들 시 문제소음의 원인을 분석하고 저감하는데 필요한 관련이론의 적용과 이에 수반되는 데이터측정, 데이터처리 및 데이터 해석과정을 자세하게 기술하였다. 소음진동 측정 및 분석 결과 문제의 소음은 엔진의 회전 2.5차 성분을 가지고 구조기인소음이었다. 아이들 시 문제의 실내소음에 영향을 미치는 구조전달경로들의 기여도를 분석하기 위해 소음경로해석시험 및 모드시험을 실시하였다. 시험분석 결과에 따라 기여도가 놓은 배 기계 및 트랜스미션계의 진동 전달특성을 개선하므로써 만족할 수준의 소음 저감효과를 얻었다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.148-154
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• 1996

가정용 냉장고에 있어서 정음화를 위한 다각적인 노력이 냉장고의 주요 소음원이라고 할 수 있는 압축기, 냉기 순환용 팬, 압축기 냉각용 팬 및 냉매 순환용 파이프 방진구조 등의 개선을 통하여 국내외적으로 상당한 진척을 보이고 있다. 이러한 소음원들의 특징은 각각이 특정한 목적에 의하여 작동하는 하나의 구동부이거나 이러한 구동부와의 직접적인 연결에 의해 가진되는 경우로서 Airborne Noise나 Structureborne Noise를 발생시키고 있다. 본 논문에서는 이러한 압축기나 팬이 꺼진 상태에서 냉장고의 싸이클상에 열교환용 냉매가 봉입된 상태에서 압축기가 운전시 형성되었던 싸이클상의 고압 및 저압측의 압력 차이에 의하여 증발기의 Accumulator내에 형성된 Sleeve(이하, 삽입관 .PHI.1.5 Hole)에 의해서 발생되는 Bubble 소음에 대한 실험적 규명과 소음 측정을 통한 주파수 분석을 하였으며, 이러한 Bubble 소음 발생시 싸이클상의 온도 및 압력값을 측정하여 Strasberg에 의해 도출된 선형화된 식을 이용하여 Bubble 소음 발생시 주파수 분석을 통한 Bubble Size를 결정하였고, Bubble 소음 발생의 직접적인 원인으로 작용하는 Orifice를 제거하여 Bubble 소음의 개선 정도를 비교 검토하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.53-58
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• 1990

The use of spreadsheet packages for solving noise control problems has been cited by several authors, eg Saha[1] and Thornton[2]. The effectiveness of using spreadsheet packages compared with the traditional computer programs written in high level languages was demonstrated when applied to relatively simple problems, such as the selection of hearing protectors or the prediction of noise equation which includes logarithmic additions at most represents the physics of the problem. The simplicity of the governing equation together with the requirement to handle a vast amount of data are considered to be the major reasons for noise control engineers to use spreadsheet packages. Although shipboard noise prediction seems to be very complicated, the calculation procedure itself is, in essence, identical especially true for prediction methods based on empirical formulae[3,4], ie the procedure that consists of the three basic elements, ie source, path and receiver. This paper discusses the application of spreadsheet package LOTUS 1-2-3 to shipboard noise prediction problems. A utility program of the package is written using macro functions and is shown to be especially useful for noise control engineers who are unfamiliar with spreadsheet packages. In addition, a new type of empirical formula, to estimate structureborne noise transmission loss, is proposed.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.268-274
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• 1991

The methods of prelimiuary noose prediction by Janssen, Buiten, etc are introduced. The distribution of noise levels in newly built ships are investigated. A new procedure for noise prediction is proposed which reflects the results of the investigations. The dominant noise souroes(M/E, D/G) are regarded as one virtual source. The structureborne transmission loss are divided into vortical and horizontal components and the latter component depends on the number of decks as well as the number of frames. The all considered cabins are standardized with typical cabins which have the same acoustic properties. The measured and predicted noise levels are compared In the tables.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.1
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• pp.133-141
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• 1994

In this paper, experiences obtained during the development of MASS(Noise Analysis of Ship-board using SEA) are described. The results are summarized as follows. (1) The modelling techniques for ship structure and cabins are suggested. (2) Structureborne and airborne noise for a real ship were measured at sea trial and predicted by NASS. The differences between the two values are acceptably small for the cabins located on higher decks, although problems related with modelling of lower decks and evaluation of radiation efficiency were found.

• Journal of the Society of Naval Architects of Korea
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• v.28 no.2
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• pp.293-306
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• 1991

During the last few years recommendations or regulations concerning permissible noise levels on shirts have been issued by the authorities in most countries. For these reasons the need for useful and accurate noise prediction computer programs has been emphasized. A noise prediction program can make it possible to find the most economical solution to achieve a certain noise requirement. This paper attempts to develop a noise prediction computer program using statistical energy analysis(SEA). In this paper, the SEA is used to predict the sound transmission loss for airborne noise and the vibration amplitude of the panel consisting of ship spaces such as floor, wall, and ceiling for structureborne noise. And in order to verify the prediction, a small passenger vessel, G/T120 tons, is selected. It has been shown that the prediction is capable of giving results in good practical agreement with measurements and therefore it is useful for predicting the nolle levels in ships and establishing the countermeasures at early design stage.