• 한국음향학회지
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• 제23권4호
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• pp.309-315
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• 2004

본 연구에서는 가속주행소음 (pass-by noise) 시험을 측정할 때 차량 각 부분에서 발생하는 소음 기여율을 산정하고자, 그 선행연구로 정지 차량의 좌우 측면에서 음향 인텐시티 방법을 이용하여 근접 방사소음 특성을 연구하였다. 가속주행소음 측정구간의 엔진 회전수 대역인 2,800 rpm과 3,200 rpm으로 구분하여 시험차량 중심축 선을 기준으로 7.5m 떨어진 지점에서 음압을 측정하여 주파수별 지향특성을 해석하였다. 이 결과는 차량 소음 저감에 응용할 수 있다.

• 한국산학기술학회논문지
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• 제16권4호
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• pp.2844-2850
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• 2015

철도의 운행으로 인하여 발생하는 다양한 소음 중 큰 부분을 차지하고 있는 전동소음의 경우 차륜과 레일의 접촉에 의하여 진동과 이로 인한 소음방사가 발생하므로, 레일 진동에 대한 특성과 이로 인한 방사소음과의 상호연관성 및 특성의 파악이 필요하다. 본 연구에서는 레일의 유한요소 모델을 구성하고 경계요소법을 이용하여 진동으로 인해 발생하는 소음방사를 예측하였다. 입력으로는 레일에서의 진동속도 계측치를 이용하였고 소음방사 예측결과를 계측결과와 비교하여 해석기법의 신뢰성을 검증하였다. 또한 레일 감쇄 특성에 따른 소음방사 특성을 주파수 영역에서 검토하여 레일 댐핑재의 적용에 따라 약 3dB(A)의 방사소음 저감 효과가 있음을 확인하였다.

• 소음진동
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• 제8권2호
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• pp.239-250
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• 1998

Traditionally, intake noise from internal combustion engine has not recevied much attention compared to exhaust noise. But nowadays, intake noise is a major contributing factor to automotive passenger compartment noise levels. The main objective of this paper is to identify the mechanism of generation, propagation and radiation of the intake noise. With a simplest geometric model, one of the main noise sources for the intake stroke is found to be the pressure surge, which is generated after intake valve closing. The pressure surge, which has the nonlinear acoustic behavior, propagates and radiates with relatively large amplitude. In this paper, unsteady compressible Navier-Stokes equations are employed for the intake stroke of axisymmetric model having a single moving cylinder and a single moving intake valve. To simulate the periodic motion of the piston and the valve, unsteady deforming mesh algorithm is employed and Thompson's non-reflecting boundary condition is applied to the radiation field. In order to resolve the small amplitude waves at the radiation field, essentially non-oscillatory(ENO) schemes with an artificial compression method (ACM) are used.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.268-272
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• 2002

A study to determine the structure-borne noise radiated by a dash panel of a real car is performed by using the finite element method (FEM) and the boundary element method (BEM). The radiation efficiency is used to estimate the structure-borne noise radiated by a dash panel. The curved surfaces of a dash panel change the radiation efficiency. Experimental results of radiation efficiency of a simple rectangular plate and a dash panel show good agreements with the simulation results.

• 환경영향평가
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• 제23권1호
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• pp.29-37
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• 2014

Exact and precise noise measurement is the basis for the reduction measure R&D, impact assessment and prediction modeling for railway noise. In this study, research trend as well as national and international noise measurement standard are investigated. For the estimation of vertical radiation characteristics of railway noise, specially devised zig was used. From the noise measurement and analysis, exact noise height radiated from the railway was characterized. The obtained results will be used for the suggestion of the height of microphone position of railway noise measurements.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문초록집
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• pp.337.1-337
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• 2002

In order to control the railway noise, the radiation characteristic of the noise during the train passage should be analyzed. Generally, the major noise sources for Korean Train Express are the rolling noise and power unit noise up to 300km/h. In this paper, we describe on a train model that is considered to be a row of point sources to calculate the radiation characteristic. The calculation results are compared with short distance measurement. (omitted)

• 한국소음진동공학회논문집
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• 제24권10호
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• pp.763-769
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• 2014

This study is on the experiment and prediction of the pipe noise due to the internal fluid. The vibration of pipe external surface and noise in air were measured according to the internal fluid velocity and pipe type. In the experiment, the vibration and noise level of the straight pipe and rounded pipes show that the vibration and noise level are almost same. The 900 mitred pipe shows the high vibration and noise level. In the prediction of noise due to the internal flow, the method using the pipe surface vibration and radiation efficiency shows good agreement with experimental result.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.811-812
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• 2007

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.612-615
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• 2003

In this paper, a design of radiation detector for gamma column scanner is introduced. Distillation column is important unit in Petro-chemical industries, and its on-line diagnose is very important. To get density profile measured by the radiation transmitted through column is well method for on-line diagnose as gamma scanning. For this purpose radiation detection circuit, radiation source and mechanical system for moving source and detector are required. Conventional radiation detection circuit for this application is sensitive to electric noise because of interface between the radiation circuit and the controller for mechanical system. The radiation detection system introduced here is using loop coil instead of slip ring to remove contact noise. Radiation detection system designed here for gamma scanning consist of BGO detector, high voltage circuit, PHA circuit and FSK modem. The BGO detector is used as radiation sensor, high voltage circuit and peak height analysis circuit is essential to process the signal generated from BGO detector. Micro controller convert measured data into ASCII data. FSK modem transmit ASCII data. Transmitted ASCH data is picked up in antenna coil and processed for combined function with mechanical system. This method gives good result by isolating the controlling circuit of mechanical system from radiation detecting circuit which is sensitive to noise.

• 한국소음진동공학회논문집
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• 제18권4호
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• pp.439-447
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• 2008

One of the key elements in efforts to minimize noise radiation from a powertrain is the knowledge of the main radiating component and the relation between the surface vibration of a powertrain and the sound pressure. In this research, the powertrain model is developed based on FEM(finite element method). This model is applied to the prediction of the vibration of a powertrain by using ADAMS and the radiation noise by using BEM(boundary element method). According to this numerical analysis, the surface vibration of a powertrain is investigated as a source of radiated noise. This surface vibration is caused by the 1st order natural vibration of the cylinder block and its mode shape is the torsion mode. Therefore, this mode shape is modified to reduce the surface vibration of the powertrain. The radiation noise of the modified powertrain is also reduced to $5{\sim}12\;dB$. This modification is very successful for the noise reduction based on the CAE technology.