• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1371-1379
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• 2012

This paper presents a method for estimating the contribution of vibration sources in gasoline direct injection engine parts with a multiple-input system. A partial coherence function was used to identify the cause of the linear dependence indicated by an ordinary coherence function. To apply the partial coherence function to vibration source identification in the powertrain system of a gasoline direct injection engine, a virtual model of a two-input and single-output system is simulated. For the validation of this model, the vibration of the powertrain parts was measured by using triaxial accelerometers attached to the selected vibration sources-a high-pressure pump, fuel rail, injector, and pressure sensor. After calculating the partial coherence between each source based on the virtual model, the vibration contribution of the powertrain system is calculated. This virtual model based on the partial coherence function is implemented to determine the quantitative vibration contribution of each powertrain part.

• The Journal of the Acoustical Society of Korea
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• v.35 no.2
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• pp.118-124
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• 2016

In this paper, contribution analysis method using a partial coherence function is dealt with in the case of underwater radiation noise. When performing the contribution analysis using a partial coherence function, it is important to select the order of system input. But in the case of frequency correlated systems, it is very difficult to properly select the order of system input. In order to solve this problem, the contribution analysis is performed by subdividing the area of contribution using multiple coherence function. And the new contribution analysis method is presented by using the relationship between the contribution characteristic matrix and multiple coherence function. In order to validate the new method, calculation is performed about multi-input / single-output model which is composed of sine waves. The result of calculation shows that it is possible to derive the exact contribution values.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.4
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• pp.347-354
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• 2009

Frequency analysis is one of the most useful way to analyze response signal for the purpose of grasping the dynamic characteristics of system through Fourier transformation. Although it is very effective way for frequency analysis, it is hard to analyze out a specific sound or vibration component which is correlated with others. In this thesis, source contribution analysis tool for NI-PXI equipment is developed with LabVIEW using coherences of MISO(multiple-input single-output) model. For the purpose of examining propriety of developed tool, simulation is performed with several correlated signals that have different frequency range. After checking the OCF(ordinary coherence function) and PCF(partial coherence function) of the each signal for concerned frequency domain, an experiment is conducted on an evaporator that cause the principal noise of a refrigerator. This developed tool will be expected to build up more convenient and serviceable measurement system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.8
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• pp.741-746
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• 2007

In this study, transfer path identification and output estimation are simulated by multi-dimension spectral analysis method (MDSA). Multi -input/single-output system give expression the vehicle suspension which each inputs are correlated reciprocally. In case of correlating with inputs, the system needs separating the each input signal by MDSA. Main simulations are about finding effective input by coherent output spectrum and selecting optimal input's number by multiple coherence function. Also, by shielding transfer path of each input, transfer path characteristic is identified in terms of overall integrated contribution level.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.3-8
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• 1990

소음/진동 문제를 해결하는 데 있어서 우선은 소음/진동원들의 위치를 알아 내고 그들 중에 비중이 가장 큰 소음/진동원을 파악하는 것이 중요하다. 다 입력/단일출력 모형을 이용한 소음/진동원 규명에 대한 방법에는 주파수 응 답함수를 이용하는 방법(frequency response function approach)과 부분 기여 도 함수(partial coherence function)를 이용하는 방법 등이 있는데, 입력들 사이의 상호상관(correlation)이 없는 경우에는 전자의 방법을 사용하여 출력 에 가장 큰 비중을 차지하는 소음/진동원을 알아낼 수 있으나 상호상관이 존 재하는 경우에는 후자의 방법을 사용하게 된다. 그러나 후자의 방법을 적용 함에 있어서도 기본적으로 소음/진동원들의 위치를 알아야 하는 것 이외에 그들 사이의 원인.효과관계(causaling), 또는 우선순위(rank)를 우선적으로 아 는 것이 중요한데 이는 입력들 사이의 우선순위를 어떻게 두느냐에 따라 해 석 결과가 다르게 나타나기 때문이다 [1,2,3]. 본 연구에서는 부분 기여도 함 수를 이용하여 소음/진동원을 규명할 때 그들 사이의 우선순위를 결정하는 방법을 제시하고 2입력/1출력 모형에 대해 적용하여 보았다.

• 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 the Korean Vacuum Society
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• v.3 no.1
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• pp.1-7
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• 1994

전자방출에서 에너지 교환과 역온도를 새롭게 계산하였다. 전자방출에서 대체전자들에 유용한 빈상태들을 만드는 요소로 터널링 효과를 이 계산에서 고려하였다. 그것은 방출부분에서 일어나는 대체 관정을 설명하기 위해서는 빈상태를 만드는데 터널링 기여가 필수적이기 때문이다. 이렇게 계산하여 온 도와 전장의 함수로 얻어진전자당 에너지 교환은 실험결과와 잘 일치하였다. 또한 전장의 함수로 얻어 진 역온도도 실험치와 만족할 만한 일치를 보여주었다. 이 결과는 대체전자들의 평균에너지에 대한 노 팅햄-플레밍과 헨더슨의 논쟁에서 후자의 견해를 지지하는 것이다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.1
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• pp.81-88
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• 2011

The method is introduced for estimating the noise source contribution on the noise of PDP TV in a multiple-input system where the input sources may be coherent with each other. By the coherence function method, it is found that the biggest part of the noise source in the PDP TV noise is generated by the PCB boards which consume high power and produce high heat. This analysis is modeled as three-input/single-output system because the noise is generated by three main boards, X-board, Y-board, SMPS that are located close to each other. The coherence function method is proved to be useful tool for identifying of noise source. In this study, Transfer Path Analysis using MDSA is implemented to determine the quantitative noise contribution of each board for PDP TV with the rear case closed and with the rear case open. And the possibility of noise reduction is confirmed through the experimental method that isolates the most contributing board by adding sound-absorbing materials to it.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.779-784
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• 2008

This paper presents a the method for estimating the noise source contribution on the road noise of the vehicle in a multiple input system where the input sources may be coherent with each other. By coherence function method, it is found that the biggest part of the noise source in the road noise is generated by structural vibration on the mechanical-acoustic transfer functions of vehicles. This analysis is modeled as four input/single output system because the noise is generated with four wheels that mechanism of the road noise is very complicated. The coherence function method is proved to be useful tool for identifying of noise source. The overall levels of the interior noise be coherence function method are compared with those measured and calculated by the frequency response function approach using mechanical excitation test. The experimental results have shown a good agreement with the results calculated by the coherence function method when the input sources are coherent strongly each other. The estimation of the road noise indicates that significant coherent can be achieved in the vehicle interior noise.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1206-1212
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• 2008

This paper presents a the method for estimating the noise source contribution on the road noise of the vehicle in a multiple input system where the input sources may be coherent with each other. By coherence function method, it is found that the biggest part of the noise source in the road noise is generated by structural vibration on the mechanical-acoustic transfer functions of vehicles. This analysis is modeled as four input/single output system because the noise is generated with four wheels that mechanism of the road noise is very complicated. The coherence function method is proved to be useful tool for identifying of noise source. The overall levels of the interior noise be coherence function method are compared with those measured and calculated by the frequency response function approach using mechanical excitation test. The experimental results have shown a good agreement with the results calculated by the coherence function method when the input sources are coherent strongly each other. The estimation of the road noise indicates that significant coherent can be achieved in the vehicle interior noise.