• 정보처리학회논문지B
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• 제14B권4호
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• pp.273-280
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• 2007

본 논문은 2D/3D 가상환경에서 실감 사운드의 실시간 합성을 위한 $EVE-Sound^{TM}$ 툴킷의 설계와 개발결과를 제시한다. $EVE-Sound^{TM}$는 사운드 효과 계산에 필요한 장면요소를 간추리는 전처리 도구와 실시간 렌더링 API들로 구성되며, 다중 모달리티의 실감 재현을 필요로 하는 가상현실, 게임 등의 각종 인터랙티브 콘텐츠에서 사용자에게 고급 그래픽 환경을 허용하면서 동시에 사운드의 실시간 재현을 가능하게 함을 목표로 하였다. 3차원 사운드 계산이 매우 복잡하기 때문에 기존의 사운드 API들이 간단한 사운드 효과와 재생을 제공하는 것과 달리, 복잡한 가상환경에서 3차원 사운드의 원리를 반영하되 그 렌더링을 실시간화하는 데 초점을 두었고, 이를 위해 새로운 장면 간략화 및 공간사운드 계산 방법이 제시되었다. 응용 사례 및 실험, 알고리즘 분석을 통해 제시된 툴킷의 활용성 및 향상된 실시간성을 확인하였다.

• 한국소음진동공학회논문집
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• 제13권4호
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• pp.258-265
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• 2003

This paper suggests the noise reduction method of the engine cooling fan. The fan noise contribution to the OASPL of engine room was estimated and the noise source was identified for the rotating fan by sound intensity method. And the program for Predicting the noise spectrum of axial flow fan was also developed. The radiated acoustic pressure is expressed in terms of discrete frequency noise Peaks at BPF and its harmonics and the line spectrum at the broad band by the proposed noise generation mechanisms. In this Paper, it Is shown that the comparison of the measured and calculated noise spectra of fan validates the noise predicting program. And this paper presents the characteristics of the fan noise in order to modify the design parameters. Accordingly, the design parameters were determined for the noise reduction of the fan.

• 한국추진공학회지
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• 제9권4호
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• pp.9-15
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• 2005

고성능 연소기에서 주로 채택되는 기체-액체형 동축 분사기의 음향감쇠 효과를 선형 음향해석을 통해 조사하였다. 그러한 형태의 분사기는 반파장 공명기 역할을 수행할 수 있으므로 반파장 공명기와 1/4파장 공명기의 음향감쇠 특성을 비교/조사하였다. 공명기의 음향 감쇠 효과에 있어서 경계흡수계수의 영향과 공명기 길이 효과를 알아보았고, 연소실과 공명기내 유체의 음속 변화를 통해 반파장 공명기의 음향 감쇠 특성을 조사하였다. 계산 결과, 공명기의 최적 동조 길이가 짧고, 공명기내 유체의 음속이 낮은 조건에서 큰 감쇠효과가 나타남을 알 수 있었다. 또한, 경계흡수계수의 감소는 공명기의 동조 길이 범위를 좁게 하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.114-117
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• 2006

The air filter in engine intake system has a function of filtrating the dirt in the scavenging air as well as attenuating the noise. The noise attenuation within the air cleaner filter, however, has been regarded as negligible by the field engineers. In this paper, for the analysis of the acoustical performance of air filter, an acoustical model was suggested and the characteristics of air filter system were investigated. Fibrous structure of the filter element was modeled as a micro-perforated panel using the flow resistivity and porosity. The pleated geometry of the filter element was modeled as two coupled ducts that have permeable walls, in which each duct area was assumed being constant. Using such simplified geometry, a mathematical model was developed for the sound propagation within a narrow duct system. Visco-thermal effect was considered in modeling the sound propagation through such tubes; the filter box was modeled as a rigid rectangular box. By combining two models, a four-pole transfer matrix was derived. For the validation purpose, transmission loss was measured for a plastic rectangular box containing an air filter. A noticeable effect of the air filter element was observed by including the filter into the box. Comparing the predicted and measured data, we found that the predicted TL agrees well with experimental results, in particular, in magnitude and frequency at TL troughs.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.193-198
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• 2004

In order to keep the market competitiveness, it is desirable for automotive manufacturer to meet the customer's various aspects of requirements. The overall NVH (Noise, Vibration, and Harshness) performance has been an important measure when evaluating overall vehicle performance, product quality, and enhancing customers' loyalty to the product. The noise and vibration, while the engine is idling, has been brought particular attention to the drivers and passengers, because they encounter the operation conditions quite frequently without other masking noise sources: wind noise, road noise, and even powertrain radiated noise at higher speed driving. The specific noise, defined as 'CHIT' noise, has been identified as a potential customer issue, from the Pickup Truck with newly developed V8 powertrain. This paper describes the definition of the noise, identifying the potential sources, and noise radiation mechanisms, based on series of powertrain and vehicle test and verification processes. Then, based on the root-cause identified, the design change has been proposed and validated with several vehicles in order to have a complete satisfaction of the customer.

• 소음진동
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• 제10권5호
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• pp.775-782
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• 2000

Being carried out a number of studies for the resilient mounting system of automobile engine than that of the studies for marine engines, many research results for the case of the resilient mounting system of the automobile engine have applied in the analysis for the case of marine engine. However, the size and the power of automobile engines are not only relatively small but also their operating conditions are quite different form those of marine engines. For the analysis of the automobile engine Wavelet shrinkage, misfire condition and unload condition have not been considered. Accordingly , it is not desirable to apply the results obtained form the case of automobile engines to the case of marine engines. In this study , exciting and damping forces working on the marine engine are formulated mathematically in order to apply to the design of a resilient mounting system of engine effectively. futhermore, some mathematical formulation for the analysis of the transmissibility of multi-body system are proposed. A new computer program which is able to calculate the free vibration, the transmissibility and the forced vibration of a resilient mounting system has been developed, As an application of this developed computer program, the dynamic behavior of resilient system with an actual rubber spring for the case of 6-degree-of-freedom system and 36-degree-of-freedom system are evaluated quantitatively.

• 한국음향학회지
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• 제39권4호
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• pp.322-330
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• 2020

본 연구에서는 미국 캘리포니아주 소재 반덴버그 공군기지(Vandenberg Air Force Base)에서 3차례 발사된 Falcon 9의 원거리장 소음에 대해 논하였다. 발사 소음은 3회 모두 롬폭(Lompoc) 도시 인근의 동일 위치에서 측정되었다. 전체 음압레벨(overall sound pressure level)은 3회 모두 유사하지만 기상조건과 관련된 차이점이 발사 초반부에 관찰되었다. 음압레벨 기준 최대 지향성은 약 65°로서 수평 정적 연소시험으로부터 얻어진 결과와 일치하였다. 세번째 발사 소음에 대하여 각 발사 단계에 따른 파형 및 스펙트럼을 분석하였다. 1단 엔진 추진 구간에서 소음의 대역폭은 시간에 따라 감소하였으나 그 크기는 모든 주파수에 걸쳐 주변 소음레벨을 상회하였다. 또한, 발사 후반부 데이터에서 관찰되는 특이 경향은 1단 엔진 정지 및 2단 로켓 점화와 연관이 있는 것으로 추정되었다.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.148-156
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• 2001

Computational Fluid Dynamics (CFD) analysis was carried out to investigate exhaust gas flow and acoustic characteristics in the exhaust system of a passenger car. Transient 3-dimensional flow field in the front and rear mufflers was simulated by CFD and far-field sound pressure was modeled by a simple monopole source method. Engine performance simulation was also performed to obtain the boundary condition of instantaneous fluid flow variation at the inlet of the exhaust system. Detailed exhaust gas flow characteristics such as velocity and pressure distribution inside the mufflers were presented and the pulsating pressure amplitude was compared at several positions in the exhaust system to deduce sound pressure level. The present method of the acoustic analysis coupled with CFD techniques would be very effective for the prediction of sound noise from vehicle exhaust systems although the effects of the inlet boundary condition and heat transfer on the accuracy of the prediction have to be validated through further studies.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 추계학술대회 논문
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• pp.85-90
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• 1996

In order to detect and suppress chatter in turning processes a stability control methodology was studied through manipulation of spindle speeds regarding to chatter frequencies. The chatter frequency was identified by monitoring and signal processing of sound pressure during turning on a lathe. The stability control methodology can select stable spindle speeds without knowing a prior knowledge of machine compliances and cutting dynamics. Teliability of the developed stability control methodology was verified through turning experiments on an engine lathe. Experimental results show that a microphone is an excellent sensor for chatter detection and control

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.534-537
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• 2011

This Paper present prediction Vehicle Interior Noise using ATF(Acoustic Transfer Function) and engine radiated sound power. This is useful tool to qualifying the effectiveness of Air-borne noise Path. Furthermore This method provide acoustic package performance of the vehicle and able to prepare frequency band to same segment or benchmarking vehicle.