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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
The Journal of the Acoustical Society of Korea
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Journal DOI :
The Acoustical Society of Korea
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Volume & Issues
Volume 7, Issue 4 - Aug 1988
Volume 7, Issue 2 - Apr 1988
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Vibration Control of Elastic Systems
Lee, S.J. ; Ha, Y.K. ; Park, Y.P. ;
The Journal of the Acoustical Society of Korea, volume 7, issue 2, 1988, Pages 5~19
The feedback controllers for the active vibration control of elastic systems are developed using optimal regulator, optimal tracking, time optimal and noise observer algorithms. Using the modal analysis of the elastic systems, the effects of the actuator positions, the input weighting factor and the magnitude of the constraint of the actuator force are investigated.
A study of estimation for excess attenuation of Noise propagated on the ground
Oh, J.E. ; Kim, D.G. ; Yim, T.K. ;
The Journal of the Acoustical Society of Korea, volume 7, issue 2, 1988, Pages 20~25
This study is to explain the characteristic of excess attenuation on the ground through the outdoors experiment about noise propagation and the reduced model experiment of acoustic. The outdoors experiment on the attenuation of noise propagation was tried with the small engine that had large acoustic output, and then it was conformed that there was relationship between the excess attenuation calculated by measurement from distance attenuation and Log(D/(Hs+Hr)). As a result, it was found that the attenuation of noise propogation depended upon the direction of the wind and frequency and was regressed in a straight line. And the numerical values of excess attenuation on the ground could be calculated by regarding Log(D/(Hs+Hr)) as a parameter with an airing resistance
. It was found that when the mean square error between the excess attenuation calculated by measurement and the value calculated by a fomula
was least, the optimal decision of u was made. As the characteristic of model is the model experiment on a reduced scale of 1 to 40, It was conformed that it corresponds enough with the measurement value with measuring the distance attenuation in the large anecoic chamber.
The Comparative Study of the Methods Estimating the Impulse Response of a System with Long Reverberation Time using Discrete Fourier Transform (DFT)
Kim, C.D. ; Masato, Abe ; Kenitikido, ;
The Journal of the Acoustical Society of Korea, volume 7, issue 2, 1988, Pages 26~38
This paper describes three methods for the estimation of the impulse reponse in an indoor acoustic transfer system which rather has long reverberation time by the cross spectrum. The first method, which is the conventional one, will use the white noise as the source signal. Therefore, the very long time window data and numerous number of DFT are necessary for this estimation. The second method has been disigned in order to shorten the length of time window of the first method by using a burst of noise as the source signal. The third method which will be suggested in this paper uses too types of definite signal with short duration time of the source signal. According to the view point of computation capacity, and estimation accuracy of the impulse response, the compared experimental results show that the third method will be better than the others.
On Estimating Magnitude-Squared Coherence Functions Using Frequency-Domain Adaptive Digital Filters
Kim, D.N. ; Cha, I.W. ; Youn, D.H. ;
The Journal of the Acoustical Society of Korea, volume 7, issue 2, 1988, Pages 39~50
It is proposed to use a pair of frequency-domain adaptive digital filters to estimate the magnitude squared coherence (MSC) functions of two signals. Such a method requires less computations than the LMS-MSC algorithm in which the least mean square (LMS) algorithm is applied in the time domain to compute the coefficients of a pair of adaptive digital filters. The frequency-domain adaptive digital filtering algorithms considered in this paper include the constrained frequency domain LMS (CFLMS) and the unconstrained frequency domain LMS (UFLMS) algorithms. The performance of the proposed methods are compared with those of the LMS-MSC algorithm.
A Styudy on the Implementation of Frequency Synthesizer for the Fast Frequency Hopping Spread Spectrum Communication system
Kim, W.H. ;
The Journal of the Acoustical Society of Korea, volume 7, issue 2, 1988, Pages 51~64
The frequency synthesizer thar has very short transient time is the key to construct the Fast Frequency Hopping(FFH) system. A Direct Digital Frequency Synthesizer(DDFS) whose transient time is in the nS range has been implemented and the performance of which has been examined through this paper. And by considering the hopping characteristic it is confirmed that the DDFS is suitable for the FFH system. Finally an improvement method which can greatly enhances the SNR with the state-of-the-art techniques and simplifies the system design is presented.
A study on the characteristic of material using V(z) curve of acoustic microscope
Moon, G. ; Ko, D.S. ; Jun, K.S. ;
The Journal of the Acoustical Society of Korea, volume 7, issue 2, 1988, Pages 65~73
In this paper, V(z) curve has been analyzed theoretically and compared with the experimental result, and the relation between the V(z) curve and the material characteristic has been studied. Angular spectrum and ray optics theory have been used for theoretical analysis and the acoustic microscope operating at a center frequency of 3 MHz has been used for experiment. In experiment, it has been shown that each material has a V(z) curve of a unique form and the interval of dips appearing in the V(z) curves have been used to determine the Rayleigh wave velocity.
1988년도 춘계 일본음향학회 연구발표회 참관기
The Journal of the Acoustical Society of Korea, volume 7, issue 2, 1988, Pages 74~76