• The Journal of the Acoustical Society of Korea
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• 제14권4호
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• pp.100-108
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• 1995

This study is aimed to show that revised prediction method in road traffic noise after comparing prediction method of National Institute of Environmental Research with that of the Acoustical Society of Japan. For this purpose, prediction equation and caluation procedure of each case was programmized and data predicted by each method were compared with those measured in the 14 fields. The result show that data predicted by 14 fields. The result show that data predicted by the method proposed in this study were closer to the data measured in the fields than those predicted by National Institute of Environmental Research and the Acoustical Society of Japan in the surroundings of urban express way (include highway) and general traffic road where the vehicle speed is higher than 40km/h.

• Journal of the Korean Society of Marine Environment & Safety
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• 제21권6호
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• pp.751-758
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• 2015

Noise prediction for HVAC(Heating, Ventilating and Air Conditioning) systems are normally performed by empirical method suggested by NEBB(National Environmental Balancing Bureau, 1994). However, the method is not suitable for large ducts in ships. In this paper, computational analysis methods are used to develop a noise prediction method for the large ducts in ships. To develop regression formula of attenuation of sound pressure level in large ducts, Boundary Element Method(BEM) is used. BEM and Computational Fluid Dynamics(CFD) are applied to the analysis of flow-induced noise in ducts with stiffeners inside. Loud noise above 100 dB can be generated in some cases. Breakout noises of large ducts are also analyzed by using BEM and Finite Element Method(FEM). The acoustic pressure level shows about 10-15dB difference between inside and outside of the duct. Utilizing the results of this study, it is expected that shipyard planners can predict noise of the HVAC system for ships.

• Proceedings of the Korea Information Processing Society Conference
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• 한국정보처리학회 2023년도 추계학술발표대회
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• pp.1108-1109
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• 2023

본 논문은 선박 내부 소음을 효과적으로 감소시키기 위한 ANC(Active Noise Cancellation)및 인공 지능 (AI) 결합 시스템의 개발과 적용에 관한 연구를 다룬다. 선박 환경에서의 소음은 승원의 스트레스 증가와 불편을 초래하므로, 이를 해결하기 위한 방법을 제안하고자 한다. 외부 소음과 내부 소음 데이터를 수집하고, STFT(Short-Time Fourier Transform)알고리즘을 통해 소음 데이터를 분석 가능한 형태로 전처리한다. 그 후, LSTM(Long Short-Term Memory)알고리즘을 사용하여 선박 외부에서 발생한 소음을 입력으로 받아 내부에서 들리는 외부 소음을 예측하고 제어하는 모델을 훈련시킨다. 이후 최적화 과정을 거쳐 예측 소음의 반대 파형을 생성 및 출력을 통해 ANC 를 구현한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.301-302
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• 2008

• The Journal of the Acoustical Society of Korea
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• 제39권2호
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• pp.77-86
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• 2020

In this study, the Eulerian/Lagrangian one-way coupling method is proposed to predict flow noise due to Blade-Tip Vortex Cavitation (BTVC). The proposed method consists of four sequential steps: flow field simulation using Computational Fluid Dynamics (CFD) techniques, reconstruction of wing-tip vortex using vortex model, generation of BTVC using bubble dynamics model and acoustic wave prediction using the acoustic analogy. Because the CFD prediction of tip vortex structure generally suffers from severe under-prediction of its strength along the steamwise direction due to the intrinsic numerical damping of CFD schemes and excessive turbulence intensity, the wing-tip vortex along the freestream direction is regenerated by using the vortex modeling. Then, the bubble dynamics model based on the Rayleigh-Plesset equation was employed to simulate the generation and variation of BTVC. Finally, the flow noise due to BTVC is predicted by modeling each of spherical bubbles as a monople source whose strength is proportional to the rate of time-variation of bubble volume. The validity of the proposed numerical methods is confirmed by comparing the predicted results with the measured data.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제14권6호
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• pp.503-511
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• 2004

In this study, for estimating responses of a controlled structure and determining the maximum control force of velocity-dependent damping devices, three estimation models such as Fourier envelope convex model, probability model, and Newmark design spectrum are used. For this purpose, a procedure is proposed for estimating actual velocity using pseudo-velocity and this procedure considers the effects of damping ratio increased by the damping device. Time history results indicate that actual velocity should be used for estimating accurate maximum control force of damping device and Newmark design spectrum modified by the proposed equation gives the best estimation results for over all period structures.

• Journal of KSNVE
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• 제4권4호
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• pp.397-403
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• 1994

본 고에서 제시한 타이어 소음발생기구에 대한 수학적 모델은 실제활용을 목적으로 정립된 것이다. 이 모델은 프로그램화 되어 타이어 패턴 소음 예측을 위한 컴퓨터 시뮬레이션에 활용되었다. 시뮬레이션에서는 전체 소음도 뿐만아니라 스펙 트럼 특성까지도 예측할 수 있으며, 몇가지 실추결과와 비교하여 만족스러운 수준 의 일치를 확인하였다. 이 기술의 장점은 저소음 타이어 개발에 따르는 시간과 돈을 크게 절약할 수 있다는 것이다. 즉 타이어 설계자가 구상하고 있는 패턴을 컴퓨터에 입력함으로서 타이어의 기본기능을 손상하지 않는 범위에서 최선의 소음특성을 갖는 패턴을 결정할 수 있다. 선진 타이어 업체들은 이미 이같은 방법을 사용하고 있는 것으로 알려져 있으며, 이제 우리도 그 수준에 도달했다고 자부할 수 있다. 그러나 모든 과학기술 이론이 그러하듯이 이 글에서 제시한 모델 역시 결코 완벽하다고 볼 수는 없다. 이 글의 내용이 국내 관심있는 학자들에게 시작할 수 있는 계기가 될 것을 기대하며, 국산 자동차의 저소음화 노력이 더욱 활성화 되기를 희망한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제35권1호
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• pp.27-32
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• 2007

this paper the acoustic signature from a supersonic nozzle is measured and compared to the result of a program developed for a gas turbine noise prediction. In order to measure the jet Mach Number, the pressure and temperature at the settling chamber was measured along with pressures from a pitot-tube placed near the exit. The results are also compared to the ones obtained with a shadow graph technique. Jet noise produced by an imperfectly expanded jet contains shock associated noise, which consist of broadband noise and screech tone noise. For subsonic condition, the directivity is dominant to the downstream direction due to turbulence mixing noise. For supersonic conditions, however, the directivity is dominant toward upstream direction due to shock associated noise. The comparison with a jet exhaust noise prediction code shows good agreement at supersonic conditions but needs to be improved at subsonic speeds.

• Journal of KSNVE
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• 제6권2호
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• pp.127-133
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• 1996

이 글에서는 부밍소음의 현상과 특성, 발생 메카니즘, 원인규명 방법 및 대책 방법에 대해 알아보았다. 개발 차량이 제작되고 나서 양산 단계까지의 NVH (Noise, Vibration and Harshness) 육성에 초점을 두어 트러블슈팅(troubleshooting) 위주로 서술 하였으나, 이단계에서 NVH 대책을 세우는 것은 시간이 오래 걸릴 뿐 아니라 대책안 적용에 소요되는 비용도 문제가 될 수 있다. NVH 성능이 우수한 차량 을 조기에 개발하기 위해서는 NVH가 고려된 설계가 필수적이다. 설계 단계에서 CAE 해석을 하여 NVH 성능을 미리 예측하고, 설계 미스가 있을 때는 차량이 제작되기 전에 미리 대책을 세움으로써 효율적인 차량 개발을 할 수 있다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제25권12호
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• pp.901-906
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• 2015

It is difficult to measure aircraft noise at many points, because the noise measurement is need to long time, 24 hours and consecutive 7 days, which results in high costs. As an alternative, movement measuring points are set to measure aircraft noise for less than 24 hours, and so it is needed to overcome the limitation of shorter measuring time. Thus, this study measured military aircraft noise on movement measuring points and conducted a comparative analysis on the data according to each measuring time. The data of measuring noise for 24 hours and less than 24 hours were compared to suggest appropriate measuring time on the movement measuring points. As a result of comparing data of measuring noise, an error was within 3 dB in case of measuring time of 3 hours, and an error was within 1 dB in case of 6 hours of measurement.