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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 18, Issue 8 - Nov 1999
Volume 18, Issue 7 - Oct 1999
Volume 18, Issue 6 - Aug 1999
Volume 18, Issue 5 - Jul 1999
Volume 18, Issue 4 - May 1999
Volume 18, Issue 3 - Apr 1999
Volume 18, Issue 2 - Feb 1999
Volume 18, Issue 1 - Jan 1999
Volume 18, Issue 4E - 00 1999
Volume 18, Issue 3E - 00 1999
Volume 18, Issue 2E - 00 1999
Volume 18, Issue 1E - 00 1999
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Frequency and Position Dependences of Acoustically Driven Refrigerating Temperature Differences
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 3~10
Investigations of temperature differences between both cnds of thermoacoustic exchanger generated by acoustic heat transport have been carried out as a function of the position of TAC(Thermo-Acoustic Couple) in a 68-cm-long duct. Fixed with the electric power at 50W, measurements were compared with the theory changing the frequency from 150Hz to 300Hz with 10Hz step. The frequency-position dependent distribution of temperature difference corresponding to the Q-values was obtained with the numerical simulation. Through this distribution, the optimum position of the thermoacoustic exchanger and the optimum driving frequency can be determined.
The Dependence of Frequency Change Perception on the Acoustics of a Listening Environment and Its Implication for the Evaluation of Room Acoustics
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 10~10
Psychophysical approaches to the room acoustics have been made in number of researches. The present study is looking at whether the listener′s perception of frequency change in rooms are dependent on the acoustics of a listening environment. P(C)s for frequency change in short tones were measured in different listening conditions. Two experiments were carried out to investigate the influence of room acoustics on the listener′s perception of frequency change, and its implication for evaluating the acoustics of listening environments were examined and discussed. It was found that the temporal and spectral contents of reflections from room surfaces might be an important factor which influenced the listener′s perception of frequency change in a reverberant sound field. This implicates that psychophysical approach by measuring listener′s frequency change perception might be an useful tool for evaluating room acoustics. However, cares should be taken, since some individual differences were found to exist with respect to the direction of frequency change.
A Study of QMSA Characteristics According to the Gap Variance between Ground Plane and Radiation Patch
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 11~16
In this paper, we designed and fabricated QMSA(Quarter-Wavelength Microstrip Antenna) for 850MHz band on the CGP-500 PTFE substrate(by CHUKOH company) with ε/sub r/=2.6, H=1.6mm(±0.08), where width of the radiation patch is .identical with that of the ground plane. A well matched feed point was obtained by experiments and this QMSA was fed by using prove feed method. The resonant frequencies and the return losses were mcasured by cutting the gap L₃ between the radiation patch and the ground plane, with a 5mm cutting length, step by step. As a result, we found that the measured return losses were decreased and the resonant frequencies were increased when the gap L₃ was shorter, especially under 10mm, unlike we had expected.
A New Morphological Analysis for the Spoken Language Translation System
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 17~22
It is difficult to integrate the speech processing systems and machine translation system in the spoken language translation system by reason that each system uses its own data and basic processing unit. So, we need a common I/O unit which is used in the whole system. In this paper, we propose a Pscudo-Morpheme as the interface between speech processing systems and language translation system. We implement a morphological analysis system for Pseudo-morpheme. The speech processing system using this pseudo-morpheme can get better result than other systems using the phrase or the general morpheme. So, the quality of the whole spoken language translation system can be improved. The analysis-ratio of our implemented system is 98.9%. This is similar to the common morphological analysis systems.
Determination of Natural Frequencies of an Engine Crankshaft Using Finite Elements
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 20~20
To get accurate natural frequencies of an engine crankshafts, finite element equations of motion are developed, taking real geometries of the shaft into account. For the crankshaft with wide crank webs, a specialized rotating web element is developed. This includes the effects of rotary inertia, gyroscopic moment, and shear. After the finite element equations are constructed, eigenvalues are extracted from the system equations to get natural frequencies, based on the Sturm sequence method which exploits the banded forms of the system matrices to reduce computations. The scheme developed can be used for the free vibration analysis of any type of spinning structures which include skew symmetric gyroscopic moment matrix in the system matrices. The results are compared with experimental data in order to confirm the study.
Optimization of the Withdrawal Weighting SAW Filter
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 23~30
In this study, we propose a new optimization algorithm for a withdrawal weighted SAW transversal filter to satisfy given, specifications such as bandwidth, ripple, insertion loss, and sidelobe rejection level. An analysis tool for the withdrawal weighted filter has been produced by means of the delta function model, and has been applied to the design of a filter consisting of an uniform input IDT and a withdrawal weighted output IDT. This optimization algorithm consists of three routines, which eventually determines eight design parameters to satisfy the performance specifications. At the first step, the number of input and output IDT fingers and their geometrical size are determined by the insertion loss specification. At the next step, the bandwidth is controlled by the change of the IDT finger position. Finally, the sidelobe rejection level is modified through the add/skip technique of IDT fingers. The algorithm in this paper is distinct from conventional techniques in that it can simultaneously consider all the specifications such as bandwidth, ripple, sidelobe rejection level and insertion loss, and optimize the geometry of the withdrawal weighted SAW filter.
Prediction of Prosodic Boundaries Using Dependency Relation
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 26~26
This paper introduces a prosodic phrasing method in Korean to improve the naturalness of speech synthesis, especially in text-to-speech conversion. In prosodic phrasing, it is necessary to understand the structure of a sentence through a language processing procedure, such as part-of-speech (POS) tagging and parsing, since syntactic structure correlates better with the prosodic structure of speech than with other factors. In this paper, the prosodic phrasing procedure is treated from two perspectives: dependency parsing and prosodic phrasing using dependency relations. This is appropriate for Ural-Altaic, since a prosodic boundary in speech usually concurs with a governor of dependency relation. From experimental results, using the proposed method achieved 12% improvement in prosody boundary prediction accuracy with a speech corpus consisting 300 sentences uttered by 3 speakers.
Comparison of Integration Methods of Speech and Lip Information in the Bi-modal Speech Recognition
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 31~37
A bimodal speech recognition using visual and audio information has been proposed and researched to improve the performance of ASR(Automatic Speech Recognition) system in noisy environments. The integration method of two modalities can be usually classified into an early integration and a late integration. The early integration method includes a method using a fixed weight of lip parameters and a method using a variable weight according to speech SNR information. The 4 late integration methods are a method using audio and visual information independently, a method using speech optimal path, a method using lip optimal path and a way using speech SNR information. Among these 6 methods, the method using the fixed weight of lip parameter showed a better recognition rate.
Performance Improvement of a Modified Perturbation Method via a Least Square Approach for Sensor Arrays
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 37~37
This paper concerns a modified perturbation method and a least square approach to synthesize an optimum beam pattern of a thinned sensor array with respect to element spacing. In the modified perturbation, the antenna spacing is perturbed iteratively such that the sidelobes are equalized via a linear programming approach. The least square approach is proposed to improve the array performance for the thinned array using the fact that the number of sidelobes is more than the number of element spacings. It is demonstrated that the least square approach performs better than the modified perturbation method.
Improving the Performance of Adaptive Feedback Cancellation in Hearing Aids
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 38~46
In this paper, two methods were proposed to improve the performance of adaptive feedback cancellation in hearing aids. One is “Orthogonality principle acoustic feedback cancellation method(Orthogonality principle method)” to track optimal solution with monitoring the instantaneous gradient, the other is a method using the CLMS algorithm(CLMS method). In many simulation conditions, adaptive feedback cancellation method proposed in this paper was much better than Greenberg method by Sum-method LMS algorithm which is known the most excellent method by now in case of system mismatch, SNR and segmental SMR. Also. Orthogonality principle method is as good as CLMS method in terms of adaptive feedback cancellation in many simulation conditions.
Efficient Rate Control by Fast Adaptive Mode Selection
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 43~43
A fast converging coding algorithm that adaptively selects the modes of macroblocks is introduced. For a given frame, the optimal modes are selected based on the decision curves that minimize the overall distortion at a given bit rate. The method proposed in this paper is different from the conventional ones in that it does not manipulate the quantizer to meet the target bit rate but it satisfies the target bit rate by finding optimal modes of macroblocks which result consistent visual quality. Lagrange multiplier of the unconstrained cost function is controlled to trigger decision curves to generate appropriate modes to meet bit rate and the curve is obtained by utilizing simulated annealing optimization technique. The algorithm is implemented within H.261 video codec and simulation results demonstrate superior visual quality.
State-Dependent Weighting of Multiple Feature Parameters in HMM Recognizer
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 47~52
In this paper, we proposed a new approach to weight each feature parameter by considering the dispersion of feature parameters and its degree of contribution to recognition rate. We determined the total distribution factor that is proportional to recognition rate of each feature parameter and the dispersion factor according to the dispersion of each feature parameter. Then. we determined state-dependent weighting using the total distribution factor and dispersion factor. To verify the validity of the proposed approach, recognition experiments were performed using the PLU(Phoneme-Like Unit)-based HMM. Experimental results showed the improvement of 7.7% at the recognition rate using the proposed method.
Comparison of the Performance of DART and EWC/SPUDT Type SAW Filters
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 53~59
Of various SPUDT SAW filter types, we select the two most common types, DART and EWC/SPUDT, and analyze their performance with the Smith equivalent circuit method. Based on the results for an exemplary case, a usual apodized SAW filter, we investigate the advantage of one type over the other, if any, in a quantitative manner. To compensate for the performance degradation that can happen in the process of the modification of the apodized filer to the SPUDT structure, we apply the triangular weighting technique to wide fingers of the IDT. Further, the variation in performance of the SPUDT structure is investigated in relation to its electrode thickness and the number of fingers. The results in this paper are expected to enable us to easily select an SPUDT type appropriate for each particular application field.
The Comparison of OC1 and CART for Prosodic Boundary Index Prediction
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 60~64
In this paper, we apply CART(Classification And Regression tree) and OC1(Oblique Classifier1) which methods are widely used for continuous speech recognition and synthesis. We prediet prosodic boundary index by applying CART and OC1, which combine right depth of tree-structured method and To_Right of link grammar method with tri_gram model. We assigned four prosodic boundary index level from 0 to 3. Experimental results show that OC1 method is superior to CART method. In other words, in spite of OC1's having fewer nodes than CART, it can make more improved prediction than CART.
Effects of the Shape and the Absorption in Reverberation Rooms on the Space Variances of the Sound Pressure Level
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 65~70
To examine the space variances of the sound pressure level for five different types (normal frequency spacing) of reverberation rooms, simulations were conducted using the Finite Element Method. In case of infinite surface impedance, nonrectangular reverberation rooms showed small Standard Deviations across the band of frequency, and in case of finite surface impedance, ideal rectangular reverberation rooms showed the similar results as those in irregular shaped reverberation rooms.
Higher Order Parabolic Equation Modeling Using Galerkin's Method
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 71~77
Exact forward modeling of acoustic propagation is crucial in MFP such as inverse problems and various other acoustic applications. As acoustic propagation in shallow water environments become important, range dependent modeling has to be considered of which PE method is considered as one of the most accurate and relatively fast. In this paper higher order numerical rode employing the PE method is developed. To approximate the depth directional operator, Galerkin's method is used with partial collocation to lessen necessary calculations. Linearization of tile depth directional operator is achieved via expansion into a multiplication form of (equation omitted) approximation. To approximate the range directional equation, Crank-Nicolson's method is used. Final1y, numerical self stater is employed. Numerical tests are performed for various occan environment scenarios. The results of these tests are compared to exact solutions, OASES and RAM results.
A Weighted Least Square Method for Optimization of Thinned Sensor Arrays
The Journal of the Acoustical Society of Korea, volume 18, issue 4, 1999, Pages 78~83
This paper concerns a least square method for pattern optimization of a thinned sensor array in which the squared error between a desired pattern and a synthesized one is minimized. A weighting function is applied in the function with respect to the array visual range for a symmetric and asymmetric configuration for sensor spacing. An exponential weighting function is proposed to control the sidelobes efficiently around the mainbeam and to generate a uniform sidelobe. The resulting pattern may be employed to eliminate incoming interferences distributed uniformly around the array visual range.