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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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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 23, Issue 8 - Nov 2004
Volume 23, Issue 7 - Oct 2004
Volume 23, Issue 6 - Aug 2004
Volume 23, Issue 5 - Jul 2004
Volume 23, Issue 4 - May 2004
Volume 23, Issue 3 - Apr 2004
Volume 23, Issue 2 - Feb 2004
Volume 23, Issue 1 - Jan 2004
Volume 23, Issue 4E - 00 2004
Volume 23, Issue 3E - 00 2004
Volume 23, Issue 2E - 00 2004
Volume 23, Issue 1_E - 00 2004
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Ultrasonic Velocity and Absorption Measurements for poly (sodium 4-styrenesulfonate) and Water Solutions
The Journal of the Acoustical Society of Korea, volume 23, issue 7, 2004, Pages 497~502
Both ultrasonic velocity at 3 MHz and absorption coefficient in the frequency range of 0.2-2 MHz were measured for poly (sodium 4-styrenesulfonate) aqueous solution over the concentration range of 5 to 25 % by weight. Pulse echo overlap method was employed to measure the ultrasonic velocity over the temperature range of 10-90 ℃ and the high-a ultrasonic resonator method was used for the absorption coefficient measurement at 20 ℃. The velocity exhibited a maximum value at approximately 55. 59, 63. 67, and 71 ℃ in 25, 20. 15, 10. and 5 wt% solutions, respectively. The velocity increased with poly (sodium 4-styrenesulfonate) concentration at a given temperature. The concentrations dependences of the relaxation frequency and amplitude showed that the relaxation around 200 kHz is related to the structural fluctuations of polymer molecules, such as the segmental motions of the polymer chains and that around 1 MHz resulted from the proton transfer reaction of the oxygen sites of SO₃. Both the absorption and the shear viscosity increase with the Polymer concentration. but decrease with temperature.
Thermal Sensitivity of the Bean Curd by Ultrasonic Irradiation
The Journal of the Acoustical Society of Korea, volume 23, issue 7, 2004, Pages 503~513
In this paper, the thermal sensitivity, i .e. the temperature rise per unit acoustic power, was newly defined and proposed as a performance parameter of a tissue mimicking material. Eatable tofu (bean curd) manufactured by a factory was selected as a sample material for the experiment. The temperature changes were measured not only with the variation of ultrasonic irradiation time, acoustic power, depth from the sample surface. and the distance from the source transducer while adjusting the frequency to 8 MHz but also with the variation of frequency while acoustic power. depth from the sample surface. and the distance from the source transducer keeping constant. As a result of a consideration for the transformation of the measured temperature changes to thermal sensitivities. the thermal sensitivity was found to be sufficient to use as a Performance parameter for tissue mimicking material. The tofu as a tissue mimicking material showed the maximum thermal sensitivity at 10 MHz, as is a significant result to imply the possibility that the thermal sensitivity of real human tissue strong1y depends on the frequency.
Position Estimation of Underwater Acoustic Source Using Pulsed CW Signal
The Journal of the Acoustical Society of Korea, volume 23, issue 7, 2004, Pages 514~520
There are many techniques for underwater source localization. These are the methods based on TDOA (Time Difference Of Arrival) estimation. beamforming techniques and high resolution techniques, etc. In this Paper we estimate the underwater source position using MCPSP (Modified Cross Power Spectrum Phase) function that is calculated on frequency domain using sensors of small number. However, the performances of the localizing method based on MCPSP function drops greatly in the case of CW (Continuous Wave) signal . In this Paper we proposed the TDOA estimation method for pulsed CW signal. In the Proposed method we composed of new segment including a edge of ping. This segment was computed by short-time energy detection. With theoretical representation the performances of the proposed method were analyzed under various environment.
Physical Modeling of a Sanjo Gayageum
The Journal of the Acoustical Society of Korea, volume 23, issue 7, 2004, Pages 521~531
In this paper we developed the Physical modeling of the Sanio Gayageum using the improved digital waveguide theory. The frequency characteristics of the Gayageum body is implemented by an inverse filtering and the impulse response of the body. We obtained the synthesis sounds of the unit sound for the Gayageum using the simulation of the straight-line fits by the changes of the fundamental frequencies depending on the Amok location. Finally. we could obtain the virtual Sanio Gayageum sounds similar to the actual Gayageum by tuning the Amok positions.
A Study on the Efficient Feature Vector Extraction for Music Information Retrieval System
The Journal of the Acoustical Society of Korea, volume 23, issue 7, 2004, Pages 532~539
In this Paper, we propose a content-based music information retrieval (MIR) system base on the query-by-example (QBE) method. The proposed system is implemented to retrieve queried music from a dataset where 60 music samples were collected for each of the four genres in Classical, Hiphop. Jazz. and Reck. resulting in 240 music files in database. From each query music signal, the system extracts 60 dimensional feature vectors including spectral centroid. rolloff. flux base on STFT and also the LPC. MFCC and Beat information. and retrieves queried music from a trained database set using Euclidean distance measure. In order to choose optimum features from the 60 dimension feature vectors, SFS method is applied to draw 10 dimension optimum features and these are used for the Proposed system. From the experimental result. we can verify the superior performance of the proposed system that provides success rate of 84% in Hit Rate and 0.63 in MRR which means near 10% improvements over the previous methods. Additional experiments regarding system Performance to random query Patterns (or portions) and query lengths have been investigated and a serious instability problem of system Performance is Pointed out.
Robust Speech Enhancement Using HMM and
The Journal of the Acoustical Society of Korea, volume 23, issue 7, 2004, Pages 540~547
Since speech enhancement algorithms based on Kalman/Wiener filter require a priori knowledge of the noise and have focused on the minimization of the variance of the estimation error between clean and estimated speech signal, small estimation error on the noise statistics may lead to large estimation error. However, H/sub ∞/ filter does not require any assumptions and a priori knowledge of the noise statistics, but searches the best estimated signal among the entire estimated signal by applying least upper bound, consequently it is more robust to the variation of noise statistics than Kalman/Wiener filter. In this paper, we Propose a speech enhancement method using HMM and multi H/sub ∞/ filters. First, HMM parameters are estimated with the training data. Secondly, speech is filtered with multiple number of H/sub ∞/ filters. Finally, the estimation of clean speech is obtained from the sum of the weighted filtered outputs. Experimental results shows about 1dB∼2dB SNR improvement with a slight increment of computation compared with the Kalman filter method.
A Study on Modified Clustering Algorithm for Text-Dependent Speaker Verification System
The Journal of the Acoustical Society of Korea, volume 23, issue 7, 2004, Pages 548~553
In this paper we propose modified LBG algorithm to minimize quantization errors. When we apply conventional LBG algorithm for speaker verification system, problems that result from small amount of training data can be generated. That is, quantization error comes from fixed-sized codebook without any consideration for speaker characteristics and splitting vector in the wrong direction worsen performance of speaker verification system. So, we propose modified clustering method that has variable sized codebook according to speaker characteristics and makes right splitting direction by finding the farthest member away from mean and then find another member from the member. Simulation results show effectiveness of the proposed algorithm.