• Proceedings of the KSPS conference
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• 2007.05a
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• pp.163-166
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• 2007

Our present study was performed to investigate acoustically the Chines normal adults' voices. 60 Chines normal adults (30 males and 30 females) of the age of 20 to 39 years oridyced systained vowel /a/ and, by analyzing them acoustically with Dr. Speech, we could get the fundamental frequency (Fo), jitter, shimmer, NNE. As results, on the average, male voices showed 1I8.1Hz in Fo, 0.186% in jitter, 1.12% in shimmer, and -13.7dB in NNE. And, female voices showed 252.4Hz in Fo, 0.186% in jitter, 0.81% in shimmer, and -1I.3dB in NNE. Every parameter except Fo showed no significant difference between male and female voices.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.333.1-333
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• 2002

This paper suggests the noise reduction method of the engine cooling fan. It was estimated the fannoise contribution at the engine room and identified the noise source at the rotating fan by sound intensity method, first. And it has been developed the program for predicting the noise spectrum of axial flow fan. The radiated acoustic pressure is expressed the discrete frequency noise peaks at BPF and its harmonics and the line spectrum at the broad band by the noise generation mechanisms. In this paper it is shown that the comparison of the measuted and calculaed noise spectra of fn for the validation of the noise predictiong program. And this paper presents the characteristics of a fan noise due to modify the design parameters. Accordingly, it was obtained the design parameter values for noise reduction of fan.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2003.11a
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• pp.59-65
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• 2003

The present article has the purpose of evaluating subjective response of Won Buddhism sanctums by psychoacoustics experiment. Furthermore, basing on this experiment, the present article makes a suggestion of a physical sound-evaluating index. To achieve the purpose, I conducted an psychoacoustics experiment at 6 sanctuaries out of the representing 40 sanctuaries of Won Buddhism sanctums, which size is bigger than 1,000 m$^3$. I made a reanalysis with 3 Buddhist sanctums out of the subjects of psychoacoustics experiment which are generally rated superior. From the result, I can make each evaluation type into two types, sound clarity and space sense of sound. Also, I make various suggestions of physical parameter, with which I can evaluate the proper sound condition for Won Buddhism sanctums.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2157-2165
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• 2007

A novel design technology for a high frequency electronic ballast for metal-halide discharge lamps is proposed. A PFC technique is adopted to get unit power factor and output frequency alteration technique is adopted to avoid acoustic resonance. For characteristics evaluation, the designed electronic ballast is presented using normalized parameter. To reduce losses of the ballast. ZVS control technique is adopted and the maximum flux density of magnetic core for inductor should be kept lower. The electronic ballast for 250[W] metal-halide discharge lamp is implemented and 96[%] efficiency and low conducted EMI level are accomplished.

• The Journal of the Acoustical Society of Korea
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• v.11 no.3
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• pp.14-24
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• 1992

This paper is a study on the consonant recognition using neural network. First, the part of consonant was separated from the sound of vowel and consonant by the use of acoustic parameter. The rate of length vs. zero crossing rate in the sound of consonant had been studied by dividing each consonant into several groups. Finally, for the purpose of consonant recognition, the composite neural network which consists of a control network and several sub-network is proposed. The control network identifies the group to which the input consonant belongs and the sub-network recognizes the consonant in each group.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.8
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• pp.367-375
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• 2001

In Underwater Flight Vehicle depth control system, the followings must be required. First, it needs robust performance which can get over modeling error, parameter variation and disturbance. Second, it needs accurate performance which have small overshoot phenomenon and steady state error to avoid colliding with ground surface or obstacles. Third, it needs continuous control input to reduce the acoustic noise and propulsion energy consumption. Finally, it needs interpolation method which can sole the speed dependency problem of controller parameters. To solve these problems, we propose a depth control method using Fuzzy Sliding Mode Controller with feedforward control-plane bias term and Neural Network Interpolator. Simulation results show the proposed method has robust and accurate control performance by the continuous control input and has no speed dependency problem.

• Proceedings of the KSPS conference
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• 2006.11a
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• pp.92-95
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• 2006

The purpose of this study is to find the acoustic parameters on frequency domain to distinguish the Korean nasals, /m, n, ng/ from each other. Since it is not easy to characterize the antiformant on frequency domain, we suggest the new parameters that are calculated by LTAS(Long term average spectrum). Maximum energy value and its frequency and minimum energy and its frequency of zero are obtained from the spectrum respectively. In addition, slope1, slope2, total energy value, centroid, skewness, and kurtosis are suggested as new parameters as well. The parameters that are revealed as to be statistically signigicant difference are roughly peak1_a, zero_f, slope_1, slope_2, highENG, zero_ENG, and centroid.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.1
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• pp.40-47
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• 2003

This study was conducted to determine the sound paths and transmitted sound level in house. An air-conditioner system was selected a typical sound source. The measured transmission loss data shows that the apertures have an significant effect on the transmitted noise and comparable with the existing theoretical data. Therefore the complex aperture was substitute to quantitative apertures approximately. An effective simulation method, ray tracing and mirror image source method, was employed in the prediction of transmitted sound level. The measured results were efficiently reflected on the simulated results. So it is important that measuring the acoustic parameter prior to the prediction of the transmitted sound level in the house.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.11
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• pp.93-101
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• 1997

Ever since the nonlinearity of machine tool dynamics was established, researchers attempted to make use of this fact to devise better monitoring, diagnostics and control system, which were hitherto based on linear models. Theory of chaos which explains many nonlinear phenomena comes handy for furthering the analysis using nonlinear model. In this study, measuring system will be constructed using multi-sensor (Tool Dynamometer, Acoustic Emission) in end milling process. Then, it will be verified that cutting force is low-dimensional chaos by calculating Lyapunov exponents. Fractal dimension, embedding dimension. And it will be investigated that the relation between characteristic parameter calculated from sensor signal and tool wear.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.975-979
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• 2002

This paper studies the indirect parameters when the new and worn end mill working in the machining center. The parameter output methods are cutting force, current values and AE signals. In the result, when the worn end mill operating, cutting forces increase the 14.71〔N〕, current values increase the 2.917〔A〕 and 1.168〔A〕 according to the spindle mote. and feed motor, and AE signals increase the 0.588$\times$10$^{-5}$ 〔A〕. We can use these parameters in the detection of end mill wear.