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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
The Journal of the Acoustical Society of Korea
Journal Basic Information
Journal DOI :
The Acoustical Society of Korea
Editor in Chief :
Volume & Issues
Volume 25, Issue 8 - Nov 2006
Volume 25, Issue 7 - Oct 2006
Volume 25, Issue 6 - Aug 2006
Volume 25, Issue 5 - Jul 2006
Volume 25, Issue 2E - Jun 2006
Volume 25, Issue 4 - May 2006
Volume 25, Issue 3 - Apr 2006
Volume 25, Issue 2 - Feb 2006
Volume 25, Issue 1 - Jan 2006
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Studying the Acoustic Impedance as a Function of Hole Area of Grille for Micro-Speaker
Oh Sei-Jin ;
The Journal of the Acoustical Society of Korea, volume 25, issue 3, 2006, Pages 101~106
In this study, the impedance behavior of micro-speaker had been investigated as a function of hole area existing on the grille. In order to theoretically study the change of acoustical property due to the different total hole area, the holes were treated as a short open pipe system, such as an orifice. This theoretical result was in an excellent agreement with the experimental one. In detail, the acoustic impedance to be caused by the hole could be greatly increased with the decrease of hole area. Therefore, it can be concluded that the acoustic property of micro-speaker could be greatly changed by increasing the acoustic impedance of hole with reducing hole area.
The Group Velocity of Lamb Wave Generated by the one Source in Unidirectional Laminated Composite Plates
Lee Jeong-Ki ; Rhee Sang-Ho ;
The Journal of the Acoustical Society of Korea, volume 25, issue 3, 2006, Pages 107~112
The elastic waves in a plate are dispersive waves due to the characteristics of Lamb waves. However, S0 symmetric mode is less dispersive in the frequency region below the first cut-off frequency. The wave Propagation velocities vary with the direction in anisotropic plates such as Carbon Fiber Reinforced Plastic (CFRP) Plates. The wave vector direction and energy flow vector direction are same in isotropic plates. However, the wave vector direction same as the phase velocity direction is not in accordance with the energy flow direction same as the group velocity direction in anisotropic plates. In this study. the dispersion curves or the phase velocity from anti-symmetric and symmetric Lamb wave dispersion equation are calculated for unidirectional laminated composite plate. Slowness surface is sketched using phase velocity under the first cut-off frequency. The direction and magnitude of group velocity are corrected with this slowness surface. The measured group velocities are in good agreement with the corrected group velocity curve except near the fiber direction zone which is called the cusp region.
Improved Equalization Technique of OFDM Systems Using Block Type Pilot Arrangement
Kim Whan-Woo ; Kim Ji-Heon ;
The Journal of the Acoustical Society of Korea, volume 25, issue 3, 2006, Pages 113~120
This paper is concerned with a equalization technique for Orthogonal Frequency Division Multiplexing (OFDM) systems based on a block type pilot arrangement over slow fading channels. The bit rates obtained in underwater channels are relatively modest compared to some other communication channels such as cellular phones or indoor wireless systems. Consequently. the Doppler effect is the important parameter in tracking a channel. In case of a coherent demodulation scheme, the residual mean phase errors due to Doppler frequency may be fatal for the performance of the system. The equalizer could not solely handle mean Doppler shift. To account for the common Doppler effect a phase error tracking loop is used with the frequency equalizer. so that the rotation errors are avoided. Furthermore. simulations show that we can reduce the computational load of the tracking loop with negligible effect on performance.
Vibrational Modes of Pyeongeong
Yoo June-Hee ;
The Journal of the Acoustical Society of Korea, volume 25, issue 3, 2006, Pages 121~128
Korean pyeongyeong, a set of sixteen L-shape chime stones covering one and one third octaves, is a standard instrument in the Korean traditional court music. We analyze the vibrational mode frequencies in a pyeongyeong replica which is played at the National Center for Korean Traditional Performance Arts and pyeongyeong remains which are exhibited at King Sejong Memorial Museum. The modal shapes on the Whangjong, the 1st stone and Cheonghyurjong, the 16th stone mapped by scanning accelerometer, TV holography and STAR system. The nominal frequencies in pyeongyeong replica at the National Center for Korean Traditional Performance Arts increase linearly with the thickness of the stones and the tones are tuned in line with the musical scale of Sambunsonik. The sexagenary cycles on the pyeongyeong remains at King Sejong Memorial. which show the Year of product indirectly, are different each other and the tones are not tuned in scale. The relative frequency ratios of each modes on stones differ more than just-noticeable differences from those on the pyeongyeong replica. Modal shapes are same for the two stones regardless of the thickness.
A Study of the Sound Quality Characteristics for Environmental Noise Assessments Parameters
Jo Kyoung-Sook ; Cho Yeon ; Hwang Dae-Sun ; Hur Deog-Jae ;
The Journal of the Acoustical Society of Korea, volume 25, issue 3, 2006, Pages 129~136
For the environmental noise assessments. A weighted equivalent noise level (LeqA) is used to measure the time varying environmental noise. However, it is not appropriately reflect various environmental noise features and human emotions. The human perception of the noise is affected largely by the psychoacoustic characteristics of noise as well as the sound pressure level In this study, the effective factors of noise qualify are analyzed using the subjective assessment and statistical analysis of environmental noise, such as road traffic noise. construction site noise, noise in daily living. and other. The analysis methodology is composed to three steps as follows : firstly, the values of the sound qualify metrics of various noise sources were analyzed. And to classify the noise sources, we conducted a cluster analysis using sound quality metrics. Secondly, subjective jury testing was carried out using the methods of paired comparisons and semantic differential. Finally, the correlation between the subjective parameters and the noise quality metrics were analyzed. As a result. the human perception characteristics of the various environmental noise are described in some physical parameters of the noise qualify metrics.
Prosodic Characteristics of Korean Distant Speech
Kim Sun-Hee ; Kim Jong-Jin ; Lee Sook-Hyang ;
The Journal of the Acoustical Society of Korea, volume 25, issue 3, 2006, Pages 137~143
The aim of this paper is to investigate the prosodic characteristics of Korean distant speech. Four speakers (2 males and 2 females) produced 36 2-syllable words in both distant-talking and normal environments. totaling 288 spoken 2-syllable words. The results showed that ratios of second syllable to first syllable in vowel duration and vowel energy were significantly larger in the distant-talking environment compared to the normal environment and f0 range also bigger in the distant-talking environment. In addition, 'HL%' contour boundary tone in the second syllable and/or 'L+H' contour tone in the first syllable were used in the distant-talking environment.
A Study on Classification of Heart Sounds Using Hidden Markov Models
Kim Hee-Keun ; Chung Young-Joo ;
The Journal of the Acoustical Society of Korea, volume 25, issue 3, 2006, Pages 144~150
Clinicians usually use stethoscopic auscultation for the diagnosis of heart diseases. However, the heart sound signal has varying characteristics due to the noise and/or the conditions of the patients. Also, it is not easy for junior clinicians to find the acoustical differences between different kinds or heart sound signals. which may result in errors in the diagnosis. Thus it will be quite useful for the clinicians to make use of an automatic classification system using signal processing techniques. In this paper, we propose to use hidden Markov models in stead of artificial neural networks which have been conventionally used for the automatic classification of heart sounds. In the experiments classifying heart sound signals. we could see that the proposed methods were quite successful in the classification accuracy.