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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of the Acoustical Society of Korea
Journal Basic Information
Journal DOI :
The Acoustical Society of Korea
Editor in Chief :
Volume & Issues
Volume 14, Issue 6 - Dec 1995
Volume 14, Issue 5 - Oct 1995
Volume 14, Issue 4 - Aug 1995
Volume 14, Issue 3 - Jun 1995
Volume 14, Issue 2 - Apr 1995
Volume 14, Issue 1 - Feb 1995
Volume 14, Issue 2E - 00 1995
Volume 14, Issue 1E - 00 1995
Selecting the target year
Thermoacoustic Refrigerating System, Part I : Acoustic Analysis and Design Procedure
Hah, Zae-Gyoo ; Ahn, Chul-Yong ; Sung, Keong-Mo ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 5~12
In this paper, acoustic analysis of thermoacoustic refrigerating system was given and the design procedure meeting the specifications was presented. The thermoacoustic refrigerator transforms the sound wave energy into the thermal energy via adiabatic process of inert gas. The system is composed of mainly three parts ; the acoustic motor utilizing loudspeaker the stack of plate for thermal transport and the resonator to form the standing wave. Based upon the acoustic analysis, resonator dimension and stack position and size were decided, and the entire refrigerating system was designed to the given specification. Also the mechanical Impedance of the designed resonator was obtained by simulation.
Thermoacoustic Refrigerating System, Part II : Implementation and Experiment
Hah, Zae-Gyoo ; Ahn, Chul-Yong ; Sung, Keong-Mo ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 13~20
In this paper, the thermoacoustic refrigerating system was implemented and its operation was experimentally verified. The system is composed of several parts ,4 inch midrange speaker, speaker housing, chamber, stack housing, stack of plates, heat exchangers, thin pipe and cavity. The system is filled with He gas at 10 bar and contains T-type thermocouples and condenser microphone for measuring the temperature and pressure inside, respectively. In addition, cooling water is used for protecting speaker from thermal destruction and cooling down the hot heat exchanger. For the experimental verification of the implemented refigerating system, electrical impedance and resonance characteristics were measured. The results showed that it was most efficient to drive the system at 340 Hz. When operated at 340 Hz,
environments and 50 electical watts, the temperature of the cold region decreased by
. The dissatisfaction mainly comes from the incomplete thermal insulation of the cold region. We also pointed out some guidelines to improve the performance for later study.
An Investigation of Mutual Radiation Impedance in a Plane Array Acoustic Transducer
Lee, Jong-Kil ; Seo, In-Chang ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 21~26
In this paper integral equations are derived and simulated numerically for the mutual radiation impedance of an acoustic transducer in a Plane array. It is assumed that the pistons are mounted in the rigid infinite baffle. The mutual radiation impedance is separated into resistance and reactance and plotted as a function of ka and kd. Mutual radiation resistance is decreased and perturbed according to increase of ka. Mutual radiation reactance is decreased along to increase of ka. Mutual impedance is decreased when kd is increased. However, when ka is 6, 13, and 19 the interaction effect is decayed. When the relative piston position of the two pistons is 45 degree, the amount of interaction becomes minimized.
The Determination method of Available Bandwidth for Automation of the Split-Spectrum Processing
Ko, Dae-Sik ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 27~31
In this paper, the determination method of available bandwidth for automation of the split-spectrum processing(SSP) has been studied. The SSP is used for the visibility enhancement of the ultrasonic signal with grain noise. Even though the SSP has proved useful in signal-to-noise ratio enhancement, its application and automation have been limited due to ambiguity in the determination of available bandwidth. Until recently, it is the usual practice to optimize the available bandwidth by trial and error. The spectral histogram is the statistical distribution of the spectral windows that is selected by the minimization algorithm with the whole band of the spectrum of the received ultrasonic signal. Since the available bandwidth can be determined adaptively using spectral histogram, this method can be used for automation of the SSP. In order to evaluate the determination technique of the available bandwidth using spectral histogram, this method is applied to experimental ultrasonic data. The experimental results show that the spectral histogram is an efficient method for determination of the available bandwidth and automation of the SSP.
Improvement of Time Resolution of the Constant Q Transform using Octave Band Filter Banks
Byun, Jeong-Keun ; Kim, Dong-Jun ; Choi, Do-Ill ; Park, Sang-Hui ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 32~39
This paper describes a method of musical frequency estimation using tree structured octave band filter banks and the constant Q spectral transform. The performances of the proposed method are compared with those of the conventional constant Q transform using FFT. The performances are evaluated by the estimated fundamental frequency, varying the bandwidth and the frequency resolutions. The results are as follows. With the same frequency resolution of the conventional constant Q transform using FFT, the proposed method gives the better time resolutions, thus, the limit of the processing bandwidth is removed. And, when the bandwidth and the frequency resolution are set high for more accurate results, the computational complexity of the proposed method is less than that of the conventional one.
Measurements of Acoustic Properties of Materials by Spectral Analysis of Ultrasonic Pulses
Ha, Kang-Lyeol ; Kim, Moo-Joon ; Lee, Jong-Kyu ; Kim, Sung-Boo ; Noriyoshi, Chubachi ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 40~47
A system for measurement of ultrasonic velocity, attenuation and complex modulus of materials by using the spectral analysis method of pulses has been constructed and its performances are estimated. The system has a mechanical scanning part of an acoustic microscope with a ZnO plane wave transducer of the resonant frequency of 85MHz. Ultrasonic velocity has been obtained by the intervals of maxima (or minima) on the power spectrum of a pulse train reflected from the surface and bottom of a specimen, and attenuation has been obtained by the power spectra of three pulses reflected from the surface and the bottom of a specimen and the surface of a standard specimen. The measured results for materials such as fused quartz, polyester show that the system has very high accuracy.
The Prediction of Road Traffic Noise under Reflective Conditions
Yeo, Woon-Ho ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 48~53
A considerable number of methods are available for predicting traffic noise levels of road networks where sound is freely propagating. But surrounding buildings reflect back sound to the road and sound energy is increased by these reflectors. Therefore, this study was focussed on the establishment of the prediction method of road traffic noise under reflective conditions. This prediction method was developed by establishing prediction formulas of noise level such as
. The sound energy density was employed to establish prediction formulas in terms of independent variables. The validity of the proposed prediction formulas was been confirmed by applying them to actually measured parameters of road traffic noise and noise level data. On the whole, the agreement between measured and predicted noise levels appeared to be satisfactory. The conclusion might be reached that the method developed in this study could be used to predict road traffic noise under reflective conditions.
Recognition of Korean Phonemes in the Spoken Isolated Words Using Distributed Neural Network
Kim, Seon-Il ; Lee, Haing-Sei ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 54~61
In this paper, we implemented distributed neural network that recognizes phonemes by frame unit for the 30 Korean proverbs sentences consist of 106 isolated words. The features of speech were chosen as PLP cepstrums, energy and zero crossings, where we get those being used as inputs to the distributed neural networks in wide area for a frame to get the good temperal characteristics. A young man of twenties has produced 30 proverbs 5 times. The learning of neural network uses 4 sets of them. 1 set being unused remains for test. There exists silence between words for the easy discrimination. The ratio of frame recognition in large grouping neural network is
when 4 sets were used for the learning.
The Features Extraction of Ultrasonic Signal to Various Type of Defects in Solid
Shin, Jin-Seob ; Jun, Kye-Suk ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 62~67
In this paper, the features extraction of reflected ultrasonic signals from various type of defects existing in Al metal has been studied by digital signal processing. Since the reflected signals from various type of the defects are ambiguous in features distinction from effects of noise, Wiener filtering using AR (auto-regressive) technique and least-absolute-values norm method has been used in features extraction and comparison of signals. In this experiment, three types of the defect in aluminum specimen have been considered: a flat cut, an angular cut, a circular hole. And the reflected signal have been measured by pulse-echo methods. In the result of digital signal processing of the reflected signal, it has been found that the features extraction method have been effective for classification of the reflected signals from various defects.
New Pitch Detectors Using Morphological Filters
Jiang, Gang-Yi ; Choi, Tae-Young ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 68~73
In this paper, two new morphological pitch detectors, one in time-domain and the other in frequency-domain, are presented. The roles of structuring element in morphological filters are experimentally examined. As a result, it is shown that the new pitch detectors using suitable structuring elements are quite simple, computationally very efficient, and robust than the conventional pitch detectors.
Linear Visual Feedback Conrtol using Binocular Visual Space
Lim, Seung-Woo ; Park, Chang-Kyun ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 74~79
This paper proposes the stereo LVFC-Robot which Imitates eyes and arms of man. we derived linear approximation equation between visual space and joint space by minimum square method and then applied it to the proposed stereo LVFC-Robot. As a result of a simulation, its efficency is verified. Compared with the stereo VFC, the stereo LVFC Robot don't need the Image Jacobian and the Robot Jacobian. Thus it is possible to control Robot in real time.
Study on the Analysis of the Dynamic Characteristics of a Local Oscillator using in the Relay Systems of a Digital Land Mobile Communication
Sim, Soo-Bo ;
The Journal of the Acoustical Society of Korea, volume 14, issue 6, 1995, Pages 80~84
In the equivalent state with an actual transmission, the paper is presented the novel analysis of the dynamic characteristics of the automatic frequency control, using for QPSK relay system in digital land mobile communication, which is adopted a crass product frequency discriminator and the various kinds of frequency variances that calculate the closed loop frequency jitter are found.