• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.187-192
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• 2006

Helicopter noise has been considered as one of major design factors like a performance and safety since the public acceptance, comfortability and stealth aspects were important for customers. According to the airworthiness regulation, the noise levels in throe different flight conditions shall comply with the specific limits. Main and tail rotors noise is most dominant in far field due to the low and mid range frequency characteristics. It is an air-born noise so That the accurate aerodynamic data is necessary for the accurate noise prediction. In KARI, low noise main and tail rotors as well as analysis codes have been developed since 2000. The approach for low noise main rotor is a kind of tip modifications, so called twin vortices tip to reduce the BVI noise. Analysis results show the 9.3dB reduction in terms of pseudo EPNL. The uneven spacing concept is applied for low noise tail rotor. Three or four decibel noise reduction is achieved by new optimized uneven spacing. Rotor noise and aerodynamic prediction codes have been improved also.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.3
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• pp.280-284
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• 2011

The mass change during the molecular interaction between explosive specific bio-receptors and target molecules has been measured using quartz crystal microbalance(QCM), which has a mass change detection limit up to ~ng/$cm^2$. The environmental effect on the molecular interaction has been evaluated. In the liquid phase molecular interaction experiments, the high selectivity of the bio-receptor to DNT compared with toluene has been shown and the sensitivity for various concentrations of DNT has been demonstrated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.1244-1249
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• 2002

In this study, the physical characteristics of steel-wire sound absorbing materials with different thickness and bulk density is experimentally obtained in terms of the porosity and specific flow resistivity. Based on the experimental results, the following conclusions can be made. The porosities of steel-wire sound absorbing materials are smaller than those of general absorbing materials, which are inversely proportional to the volume densities. For the porosity measurement with a good accuracy, the dynamic correction based on the system compliance should be involved in porosity measurement. In addition, the flow condition for the precise measurement of the specific flow resistivity of steel-wire sound absorbing materials should be limited in the laminar flow region.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.337-343
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• 2012

NREL(National Renewable Energy Laboratory) Baseline controller conduct using method proposed RISO National Laboratory in Region 3. which designed the blade-pitch control system using a single degree-of-freedom model of the wind turbine. Idealized PID-Controlled rotor-speed error will respond as a second-order system with the natural frequency and damping ratio. RISO proposed specific natural frequency(=0.6 rad/s) and damping ratio(=0.7). If specific Eigen value apply to NREL 5 MW wind turbine, differ with pitch respond for simulation results of RISO report. Variation of specific eigen value investigate performance of NREL 5 MW wind turbine.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.776-777
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.292-293
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• 2012

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1984.10a
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• pp.53-56
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• 1984

This paper shows that the error probabilities for coherent and noncoherent BF나 systems combined with FH in the presence of single channel tone interference. The performance is developed as functions of the signal to noise ratio and jamming to noise ratio. A specific results for two phases of ㅠ/4 and ㅠ/2 is obtained.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.31 no.1
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• pp.37-42
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• 2023

In an effort to reduce aircraft noise, noise abatement areas are designated and notified, and noise abatement procedures are implemented. However, residents in noise abatement areas are increasingly complaining about the increase in noise, and airlines are exceeding the criteria for noise. In this study, A330-300 airplane set flight conditions that are predicted to generate the most noise when taking off 32 runway at Gimpo International Airport, and predicted the noise as the NPD curve of the INM and AEDT programs. As a result of the analysis, it was considered that the noise at a specific point would generate higher noise than the noise criteria. Therefore, to avoid exceeding aircraft noise criteria at a particular point, supplementing the departure procedures by reflecting aircraft performance under flight conditions would reduce complaints from both airlines and local residents.

• Journal of Environmental Science International
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• v.23 no.3
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• pp.387-397
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• 2014

This study is carried out to propose an empirical equation which can promptly predict the aircraft noise level at a specific point (a receptor) near Jeju international airport by using the information of the flight path data. For this purpose, Analyses of multiple linear regression with the slant distances (SD) calculated from the gate analyses of the flight path data, aircraft noise certification levels with unit of EPNL(effective perceived noise level) and noise levels measured at receptors are performed by SPSS package. From these regression analyses for approach and departure of aircraft, we can propose empirical equations which is statistically significant. The noise levels predicted by these empirical equations are highly correlated the measured data.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2368-2373
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• 2011

Traffic noise annoyance in dwelling area like private houses and apartment is becoming very important issue nowadays in South Korea. In this paper frequency analysis of the traffic noise was performed. Based on sound pressure levels analyses and its frequency content specific requirements for component of active noise control systems are formulated. Active compensational loudspeaker, microphone front end and DSP design were analysed, considered and proposed. Components specifications and design solutions are verified using modelling and experimental technique.