• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.409-412
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• 2001

Identification of systems operating in closed loop has long been of prime interest in industrial applications. The fundamental problem with closed-loop data is the correlation between the unmeasurable noise and the input. This is the reason why several methods that work in open loop fail when applied to closed-loop data. The prediction error based approaches to the closed-loop system are divided to direct method and indirect method. Both of direct and indirect methods are known to be applied to the closed-loop data without critical modification. But the direct method induces the bias error in the experimental frequency response function and this bias error may deteriorates the parameter estimation performance

• 유체기계공업학회:학술대회논문집
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• 1998.12a
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• pp.91-96
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• 1998

The broadband noise generated aerodynamically from a two-bladed axial flow fan has been measured and compared to the result of a self-noise prediction method. The prediction scheme is based on the experimental data set acquired from a series of aerodynamic and acoustic tests of two and three-dimensional airfoil blade sections. For low blade loading case the comparison showed a reasonably good agreement, but as the loading becomes larger the empirical formula overpredict the sound pressure level at high frequency range. This is probably due to the use of stationary wing data for the prediction of rotating blade case, which will be quite different in their vortex strength at the blade tip.

• Journal of Korean Society of Transportation
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• v.5 no.2
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• pp.73-80
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• 1987

Various procedures for evaluation of traffic noise annoyance have been proposed. However, most of the studies of this type are restricted for improving traffic flow. In this paper, a method to predict the road traffic noise is proposed in terms of equivalent continuous A-Weighted sound pressure level (Leq), based on a probability model. First, distribution of the road traffic noise level are investigated. second, the weibull distribution parameters are estimated by using the quantification theory. Finally, a prediction model of the road traffic noise is proposed based on the weibull distribution model The predicted values of the Leq are closely matched the measured data.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.1
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• pp.74-82
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• 2010

Power flow analysis(PFA) methods have shown many advantages in noise predictions and vibration analysis in medium-to-high frequency ranges. Applying the finite element technique to PFA has produced power flow finite element method(PFFEM) that can be effectively used for analysis of vibration of complicated structures. PFADS(power flow analysis design system) based on PFFEM as the vibration analysis program has been developed for vibration predictions and analysis of coupled structural systems. In this paper, to improve the function of vibro-acoustic coupled analysis in PFADS, the PFFEM has been extended for analysis of the interior noise problems in the vibro-acoustic fully coupled systems. The vibro-acoustic fully coupled PFFEM formulation based on energy coupled relations is extended to structural system model by using appropriate modifications to structural-structural, structural-acoustic and acoustic-acoustic joint matrices. It has been applied to prediction of the interior noise in two room model coupled with panels, and the PFFEM results are compared to those of statistical energy analysis(SEA).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.6
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• pp.431-436
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• 2002

The interior sound pressure level of the Korean high-speed train(KHST) is predicted by geometrical acoustic method. For the Purpose of assuring the prediction of Interior noise of KHST by the geometrical acoustic scheme, calculated sound level values of the Korean train express(KTX) by Identical geometrical method are compared with measured values of KTX prototype vehicle by experiment. Contribution of individual sound source of KHST vehicle Into the interior response positions is calculated and sound sources are classified in influential order. Hence, it is reasonable approach to reduce sound power of most contributing noise source first. Sensitivity of the interior response position's sound pressure level (SPL) with respect to train wall sections' transmission loss are carried on and acoustically sensitive spot is identified, for example window area for passenger cabin case. Those contribution and sensitivity analysis results are suggested to design quieter train efficiently.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.1156-1161
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• 2001

A significant trial has been performed for estimation of noise level of a cross flow fan for air conditioning system. In general, measurements of noise level of machinery require rigorous equipment involving an anechoic chamber with precision gauges. The apparatus is expensive to utilize and is not easy to construct. In this work, we adopt static pressure sensing from an ordinary pressure transducer for prediction of noise level of a rotating fan. The present procedure is finding sound pressure from the static pressure by manipulating Light-Curle equation depicts noisy energy in terms of pressure on surfaces of noise generators. Sound power level near core unit of the fan is evaluated with the present methodology in a normal laboratory room without any sound absorbers. The method is easy and shows good prediction results compared with precise measurements by using microphones.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1865-1870
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• 2000

Sound propagation along the surface of the ground can be affected by the roughness of the ground surface and the direction of the wind. Noise Source parameter and ground factor are estimated using the measured results of two points under particular environmental condition, and the noise level of arbitrary points under the same environmental condition can be estimated. The results can be used for the prediction of the noise level from a source above a plain and homogeneous ground surface with no obstacles nearby. Upward and downward conditions are also addressed in addition to ground effect. The proposed method can be utilized to estimate the noise level of specific noise environment and its validity was confirmed with the results of actual field measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.66-70
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• 2005

Noise prediction are required as part of an environmental impact assessment. Prediction method that is used to domestic environmental impact assessment of construction site and industrial site is not applied work operation rate, work position, moving noise source, inner traffic flow, work type and height of noise source etc. The BS5228 methodology is used mainly for assessment of proposed open industrial sites(mineral extraction, landfill etc.), and larger long-term construction sites(typically for major infrastructure projects). also, estimation which consider various effect factor is possible.

• Journal of KSNVE
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• v.11 no.2
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• pp.234-240
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• 2001

Recently, the regulations from the government and the concerns of people be raised to the interest in exhaust and intake noise of passenger car as much as other vehicles. In these demands, performance prediction software was developed in this paper. In this study, Robust design was used for improving the noise reduction capacity of intake system with the performance prediction software. On the basis of the existing design, length and radius of each component that was thought to be effective to the performance of intake system was selected. At first, factors are arranged by using Ll8 table of orthogonal array and then optimum value can be obtained by modified Ll6 table of orthogonal array.

• Special Issue of the Society of Naval Architects of Korea
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• 2006.09a
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• pp.65-70
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• 2006

In this paper, we introduce prediction program of HVAC system, HJNOVAC Version 2.0. The developed program adopts both the authentic empirical method suggested by NEBB and acoustic power balancing method. The program provides intuitive pre- and post- processor using modern GUI function to help efficient modeling and evaluation of cabin and HVAC component noises. To verify the accuracy and convenience of the program, we carry out noise prediction of HVAC system for 8,100 TEU Container Carrier and measure the noise levels of cabins during sea trial.