• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.5
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• pp.430-436
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• 2011

The purpose of this study is to analyze the vibration and sound generation characteristics of the sandwich panel. Two thick panels were assumed to be separated by a compliant viscoelastic core. The transverse vibration induced by an external impact was analyzed using the Rayleigh-Ritz method. For applying arbitrary boundary condition of the panels, the edges were assumed to be supported by the translational and rotational springs. The beam functions were used as the trial functions. The effect of the boundary condition and viscoelastic core on the resulting vibration characteristics was investigated. The radiated sound power was analyzed using the proposed numerical model and the Rayleigh integral. The dynamic properties of the core and the mass-stiffness-mass resonance frequency had significant influence on the impact sound.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1967-1968
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• 2008

본 논문에서는 안정성이 강화된 다중채널 적응 필터를 사용한 능동소음 제어 시스템을 제안한다. 초기에는 IIR필터의 극점을 원점방향으로 강제로 이동시켜 안정성을 확보하고, 망각인수를 도입하여 정상상태에 도달하면 최적 수렴치로 유지하게 함으로서 제어 정상상태 성능에는 영향을 미치지 않고 안정도가 강화 된 적응 IIR 필터 알고리즘을 제안한다. LMS 알고리즘의 수렴 성능을 개선하기 위한 방법으로 정규화기법을 사용하면 수렴 속도가 향상되지만 이에 비례하여 안정성이 떨어지게 된다. 소음원 입력의 파워가 시변 할 경우 적응 알고리즘의 안정성이 약화되는 문제점이 발생하는데, 본 논문에서는 Leaky LMS알고리즘과 비슷한 구조이지만 안정성이 강화된 IIR정규화 LMS 알고리즘을 제안한다. 제안한 알고리즘의 유용성을 비교 분석하기 위하여 실험을 수행하였다.

• Journal of the korean Society of Automotive Engineers
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• v.16 no.5
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• pp.1-9
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• 1994

여기에서는 승용차의 구성부품별 해석기술의 분야별로 기술동향을 찾아보고자 한다. 1. 엔진과 변속장치 분야. 1.1 파워 플랜트 강성. 1.2 음원대책. 1.3 미션분야. 2. 흡.배기계 분야. 2.1 흡.배기음. 2.2 실내소음. 3. 엔진 마운팅 분야. 3.1 마운팅 레이아웃. 3.2 마운팅 특성. 3.3 전자제어 마운팅. 4. 타이어.서스펜션 분야. 4.1 서스펜션. 4.2 타이어. 5. 보디,프레임 분야. 5.1 보디구조. 5.2 실내음. 5.3 풍절은과 그외의 음. 5.4 경량 고강성. 6. 진동.소음실험 기술분야. 6.1 계측기술. 6.2 센서. 6.3 실험 시뮬레이션. 6.4 감성의 정량화. 7. 시뮬레이션 해석 분야. 7.1 적용범위. 7.2 복합 시뮬레이션. 7.3 모델화. 7.4 감성 시뮬레이션.

• 유체기계공업학회:학술대회논문집
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• 2004.12a
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• pp.521-526
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• 2004

This paper introduces works performed for reducing high frequency noise of a reciprocating compressor. Noise in a high frequency range strongly affects sound quality as well as increases total noise level of the compressor. In order to reduce the noise, two different works were carried out. the first work was to measure the vibration Power transferred through suspension spring and discharge pipe; and the second one was to obtain operational deflection shape from cross-power spectrum measured on shell. Based on the information, Adequate structural modification of the transfer path and shell resulted in noise reduction in a high frequency range.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1273-1279
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• 2001

Precise highway traffic noise simulation and reduction require the accurate data for sound power levels emitted by vehicles, varied to road surface, traffic speed, vehicle types and makers, different from countries to countries. In this study, we have elaboratively measured domestic highway traffic noise and parameters affecting noise levels at the nearside carriageway edge. From numerical simulation using the measured results for highway traffic noise, we propose not only two correction factors to enhance the accuracy of highway traffic sound power estimation using ASJ Model-1998 but also its typical power spectrum according to road surface type. The measured and predicted highway traffic noise levels using the proposed sound power shows little difference within 1 dB.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.949-953
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• 2004

In this paper, Power Flow Boundary Element Method(PFBEM) is studied as the numerical method for the vibration and sound predictions of complex structures in medium-to-high frequency ranges. NASPFA, the sound analysis software based on PFBEM, is developed and is used for the vibro-acoustic analysis. And also the developed software is used for the prediction of interior and exterior sound fields of vibrating structures and for the analysis of the multi-domain problems. To verify the accuracy, NASPFA is applied to the prediction of the energy distribution in the simple structures, and its results are compared with exact PFA solutions. And various practical vehicle systems are modeled and the distributions of the acoustical energy density are successfully predicted.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.205-213
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• 2011

The characteristics of noise generation in the suction nozzle of a vacuum cleaner are analyzed numerically and experimentally. First, the flow resistance induced by each element in the suction nozzle of a vacuum cleaner with a double-blade rotary fan is investigated numerically and its relation with flow-induced noise and suction performance is examined in an anechoic room. The flow resistance and vorticity in the suction nozzle are calculated, and it is found that they are closely related to flow-induced noise and that the upper limit of noise reduction is only 4 dBA. This upper limit can be achieved by changing the design of the brush nozzle. Two methods for noise reduction by enlargement of flow-inlet area and by optimization of the number of blades are tested. Finally, the effects of each method are verified experimentally.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.6
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• pp.117-122
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• 2017

Cabin noise due to the electric powertrain of electrical vehicle may consists of motor noise caused by electrical mismatch and gear noise coming from reduction gearbox. These sound may be considered rather small noise compared to those of internal combustion engine, but without masking effect, the noise can be more annoying for customer. Thus, this paper demonstrates the characteristics of electrical vehicle powertrain noise, and the effect of passive damping material for the noise reduction. The typical motor noise can be affected by the motor torque. Also, it is demonstrated that the reduction gearbox may be a weak point for the noise path compared to the motor housing. With vehicle test, it is shown that the damping patch is more effective for noise reduction with deceleration condition than with acceleration condition.

• Journal of KSNVE
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• v.6 no.3
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• pp.349-355
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• 1996

For a rail traffic noise, a typical source has a length of 200m - 400m so that the noise pollution areas have been located in the transition regions where the sound level drops between 3dB/dd and 6dB/dd. Therefore, in this region, parameters such as a horizontal distance from the track, the geometry of the ground surface, the environmental effect, and the boundary impedance condition play import roles, especially in our nation's situation. In this study, modelling techniques for the finite length of noise source have been investigated in order to evaluate the rail traffic noise level. Then. noise correction value .${\Delta}$SPL for various location in the track region is represented by the non-dimensionalized horizontal and parallel distance from the track. As an application, a high speed train is examined. Beas on the noise data measured for a Eurostar in France, the sound power value per unit length $H_1$is calcuated. It turns out that$H_1$is 109 dB. Overall sound power from the highspeed train to be serviced in our country is expected to 135 dBA.

• The Journal of the Acoustical Society of Korea
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• v.37 no.4
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• pp.248-255
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• 2018

It is known that the road noise on the rear seat of a hatchback type car is worse than that of a sedan type car because of the weakness on sealing structure. Therefore, a sound sealing system and sufficient absorption/insulation performance are required. In the case of a compact segment car, however, the application of the sufficient absorption and insulation materials is limited, because of the restriction on the production cost and weight of the car. In this study, we estimate the noise transmission path on the vehicle's body structure from tires and ground using the PBNR (Power Based Noise Reduction) method which is useful in quantitative measurement. Based on these results, we suggest an alternative absorption/insulation method for the better performance of rear seat road noise reduction in a compact hatchback car.