• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.291-291
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• 2013

The interior vehicle noise due to the exterior aerodynamic field is an important topic in the acoustic design of a car. The air flow detached from the A-pillar and impacting the side windows are of particular interest as they are located close to the driver / passenger and provides a lower insulation index than the trimmed car body parts. HMC is interested in the numerical prediction of this aerodynamic noise generated by the car windows with the final objective of improving the products design and reducing this noise. The methodology proposed in this paper relies on two steps: the first step involves the computation of the exterior flow and turbulence induced non-linear acoustic field using the CAA(Computational aeroacoustics) solver CAA++. The second step consists in the computation of the vibro-acoustic transmission through the side window using the finite element vibro-acoustic solver Actran. The internal air cavity including trim component are included in the simulation. In order to validate the numerical process, an experimental set-up has been created based on a generic car shape. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. First, this paper describes the method including the CAA and the vibro-acoustic models, from the boundary conditions to the different components involved, like the windows, the trims and the car cavity is detailed. In a second step, the experimental set-up is described. In the last part, the vibration of the windshield and windows, the total wind noise level results and the relative contributions of the different windows are then presented and compared to measurements. The influence of the flow yaw angle (different wind orientation) is also assessed.

• 대한기계학회논문집A
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• 제25권1호
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• pp.153-160
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• 2001

A general procedure for the design sensitivity analysis of structural dynamic problems has been presented in frame of the FRF-based substructuring formulation. For a system response function, the proposed method gives a parametric design sensitivity formula in terms of the partial derivatives of the connection element properties and the transfer matrix of the subsystems. The derived design sensitivity formula is applied to an engine mount system. An interior noise problem in the passenger car is analyzed using the FRF-based substructuring method and the proposed formulation is adopted to study the response variations with respect to the dynamic characteristics of the engine mounts and the bushes. To obtain the FRFs, a finite element model is built for the engine mount structures, and test data is used for the trimmed body including cabin cavity. The comparison of sensitivities derived by the proposed method and the finite difference method shows that the proposed method is efficient and accurate. The proposed sensitivity analysis method indicates effectively the most sensitive location to the interior noise among the engine mounts and the bushes.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.368-372
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• 2008

Habitability is one of the most important points when a passenger ship is cruising. In particular, anti-vibration design should be considered preferentially to offer passenger a comfort cabin and leisure space. But, a passenger ship is different from a general commercial ship in the view point of the structural arrangement. It is restricted within narrow limits to reinforce wide panels and local structures of a passenger ship because of its interior design. Moreover, the allowable vibratory limits for a passenger ship are much lower than those of a commercial ship. In this study are introduced the procedure of the vibration analysis, the structural improvement method for prevention of vibration and the results of vibration measurement during exciter test and sea trials.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1148-1150
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• 2002

The exhaust system could be a dominant acoustical source in the passengers vehicle. It would be very important to obtain the acoustically good exhaust system, in order to control the cabin interior sound in automotive. In order to obtain the acoustically good exhaust system in automotive, many kinds of exhaust system should be measured, and simultaneously those results should be compared by the sound quality parameters. In this paper, in order to develop the methodology determining sound quality parameters, acoustic simulator is introduced, combining the time domain analysis and convolution analysis. As an example to verify the reliability of this method, several kinds of measurements are carried out, and the acoustically good exhaust system is selected, based on this proposed method.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.464-473
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• 2006

This paper summarises theoretical and experimental work on the feedback control of sound radiation from honeycomb panels using piezoceramic actuators. It is motivated by the problem of sound transmission in aircraft, specifically the active control of trim panels. Trim panels are generally honeycomb structures designed to meet the design requirement of low weight and high stiffness. They are resiliently-mounted to the fuselage for the passive reduction of noise transmission. Local coupling of the closely-spaced sensor and actuator was observed experimentally and modelled using a single degree of freedom system. The effect of the local coupling was to roll-off the response between the actuator and sensor at high frequencies, so that a feedback control system can have high gain margins. Unfortunately, only relatively poor global performance is then achieved because of localisation of reduction around the actuator. This localisation prompts the investigation of a multichannel active control system. Globalised reduction was predicted using a model of 12 channel direct velocity feedback control. The multichannel system, however, does not appear to yield a significant improvement in the performance because of decreased gain margin.

• 한국음향학회지
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• 제37권4호
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• pp.223-231
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• 2018

최근 여러 환경적인 요인으로 인해 기존의 자갈 도상의 터널에서 콘크리트 도상의 터널로 교체가 되고 있지만 콘크리트 도상 터널의 경우 자갈 도상의 터널 보다 소음에 악영향을 미치고 있어 부수적으로 소음에 대한 대책이 필요한 실정이다. 이러한 대책 중 하나로 흡음블록은 설치의 제약이 적고 쉽고 빠르게 설치가 가능하기 때문에 많은 철도에서 시범적으로 적용되고 있다. 하지만 실제 환경과 운영조건에서 흡음블록의 성능에 대한 검증이 필요한 실정이다. 본 논문에서는 터널 내의 흡음블록의 성능을 확인하기 위해 흡음블록의 소음저감효과의 예측뿐만 아니라 호남선의 달성터널의 일부 구간에 흡음블록 설치 전 후의 KTX 실내 소음을 측정하고 그 결과를 비교, 분석하였다. ISO 3381를 준용한 측정장비, 측정방법을 사용하여 고속철도차량 실내소음을 측정하였으며, 터널 내부 운행시간동안에 등가소음도를 계산했다. 또한 흡음블록의 주파수별 흡음특성과 객실내부 장치소음이 영향을 주는 주파수 영역의 영향을 고려하기 위하여 가청주파수 영역 전체에 대한 등가소음도 뿐만 아니라 1/3-octave band를 기초로 주파수 영역대별 영향도도 함께 분석하였다. 또한, 열차의 운행속도와 측정시의 환경조건 등을 고려하여 흡음블록의 실내소음에 대한 영향을 평가하기 위하여 달성터널 전후에 위치한 터널내부 소음 측정값을 사용하여 보정하였다. 측정 결과의 분석을 통하여 흡음블록위에서 주행 할 때 최대 6.8 dB(A) 저감량을 나타내었다. 최종적으로 열차실내소음에 대한 1/3-octave band SPLs(Sound Pressure Levels) 예측값과 실측값을 비교하여 흡음블록에 의한 소음저감 메커니즘에 대한 이해를 증진시켰다.

• 한국음향학회지
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• 제37권3호
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• pp.147-155
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• 2018

본 연구의 목적은 선형 다중회귀분석을 통해 과부하 굴삭기 소음의 불쾌감을 표현할 수 있는 음질인자를 찾고 이를 이용하여 객관적인 평가를 위한 음질인덱스를 개발하고자 하였다. 이를 위해 소음특성이 다른 굴삭기 6모델을 선별하여 과부하 조건의 운전실 소음을 녹음하고 쌍대비교법과 크기평가법에 의한 청음평가를 수행하였다. 그리고 일관성이 낮은 청음평가 결과는 군집분석을 통해 선호도 성향이 다른 2 그룹으로 분류하고 회귀분석을 실시하여 어떤 음질인자가 불쾌감(낮은 선호도)에 유의한 영향을 주는 인자인지를 고찰하였다. 그 결과 불쾌감을 표현하는 음질인자는 10 Bark까지 부분 라우드니스 인자($PN_{10Bark}$)에 따라 불쾌감을 느끼는 성향을 가진 청음 평가자 그룹과 엔진 소음($dB_{EG}$)과 유압시스템 소음의 차이($dB_1$)로 표현된 인자에 따라 불쾌감을 느끼는 성향을 가진 청음 평가자 그룹으로 구성되어 있음을 확인하였다. 그리고 쌍대비교법의 선호도 순위와 성향 분석결과를 이용하고 크기평가법과의 상관분석을 통해 신뢰도가 낮은 평가자의 결과는 제외하여 보다 신뢰성 높은 크기평가법의 청음평가 결과를 얻었다.