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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
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Volume & Issues
Volume 16, Issue 6 - Dec 1997
Volume 16, Issue 5 - Oct 1997
Volume 16, Issue 4 - Aug 1997
Volume 16, Issue 3 - Jun 1997
Volume 16, Issue 2 - Apr 1997
Volume 16, Issue 1 - Feb 1997
Volume 16, Issue 3E - 00 1997
Volume 16, Issue 2E - 00 1997
Volume 16, Issue 1E - 00 1997
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Small Crack Detection in Bolt Threads by Predictive Deconvolution
Suh, Dong-Man ; Kim, Whan-Woo ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 5~9
If small cracks in stud bolts are not detected early enough, they grow rapidly and cause total fracture. It is difficult to detect, prior to failure, flaws such as stress-corrosion cracking in thread roots and corrosion wastages using conventional ultrasonic testing methods during inservice inspection. This study show a method of detecting a small crack by digital signal processing. When ultrasonic beams travels into threads in parallel way, the echoes from each successive threads has almost the same intervals between any two signals. We can estimate the next thread signal based on previous thread signal by the predictive distance. The optimized operator is used to remove the predicted successive thread signals so that a small crack signal can be detected.
Performance Improvement of the QCELP using an Efficient LSF Coding
Kim, Hae-Jin ; Kang, Sang-Won ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 10~15
In this paper, an efficient LSF quantizer, named improved PSVQ(IPSVQ), is proposed to apply in the 8 kbps QCELP speech coder. By using 27 bits IPSVQ instead of 40 bits DPCM quantizer per frame, we can save 13 bits/frame and allocate those bits to the codebook gain and the pitch gain parameters. Hence we improve the overall performance of the QCELP codec. The enhanced QCELP shows the performance improvement of 0.9 dB SNR and 0.4 dB SEGSNR. Informal listening tests also confirm the improvement in the speech quality.
An Analysis of the Dynamic Response and Vibrational Mode for the Cantilevered Beam
Kim, Ye-Hyun ; Go, Young-Jun ; Kang, Byoung-Yong ; Chang, Ho-Gyeong ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 16~23
As analysis of the forced dynamic response and vibrational mode for the cantilevered beam is described. Experimental results are compared with the natural frequencies and vibrational modes for the cantilevered beam using the theory of Bernoulli-Euler and finite element method. We have found 1st and 2nd resonance frequency of the cantilevered beam by means of the various external frequencies,
, using magnetic transducer. And we have studied the vibrational displacement at obtained resonance frequency of the cantilevered beam. The experimental results for the nodes of cantilevered beam were 0 in 1st mode and 0,0.786 in 2nd mode. close agreement between the theoretically predicted results and experimental result was obtained for the vibrational mode.
Analysis and Prediction of Prosodic Phrage Boundary
Kim, Sang-Hun ; Seong, Cheol-Jae ; Lee, Jung-Chul ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 24~32
This study aims to describe, at one aspect, the relativity between syntactic structure and prosodic phrasing, and at the other, to establish a suitable phrasing pattern to produce more natural synthetic speech. To get meaningful results, all the word boundaries in the prosodic database were statistically analyzed, and assigned by the proper boundary type. The resulting 10 types of prosodic boundaries were classified into 3 types according to the strength of the breaks, which are zero, minor, and major break respectively. We have found out that the durational information was a main cue to determine the major prosodic boundary. Using the bigram and trigram of syntactic information, we predicted major and minor classification of boundary types. With brigram model, we obtained the correct major break prediction rates of 4.60%, 38.2%, the insertion error rates of 22.8%, 8.4% on each Test-I and Test-II text database respectively. With trigram mode, we also obtained the correct major break prediction rates of 58.3%, 42.8%, the insertion error rates of 30.8%, 42.8%, the insertion error rates of 30.8%, 11.8% on Test-I and Test-II text database respectively.
An Analysis on the Resolution of Tomographic Images in STAM
Hwang, Ki-Hwan ; Ko, Dae-Sik ; Jun, Kye-Suk ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 33~38
In this paper, we analyzed the resolution of tomographic images which can be obtained with Scanning Tomographic Acoustic Microscope(STAM) utilizing the acousto-optic effect. To realize this, lateral and depth resolutions of both ultrasonic transducer and specimen rotating device are obtained by using BFP tomographic reconstruction algorithm. Simulation results show that both rotating devices have a good depth resolution of
. For the lateral resolution, the specimen rotating device produces
in the x and y directions and the transducer rotating device produces
in the x and y directions respectively. These results imply that the specimen rotating device is more suitable for STAM system construction.
An Analysis of Photoacoustic Signals Excited by Excimer Pulsed Laser
Yi, Chong-Ho ; Jun, Kye-Suk ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 39~46
In this paper, the PA(PhotoAcoustic) signals excited in metals by Xef, KrF excimer laser pulse were detected by a PZT transducer, and its transforming machanism and directivity patterns were analysed. The laser energy density in irradiation spot divides the PA trasnsorming machanism to be classified into thermoelastic and plasma regime, and the transforming machanisms in two regimes are different from each other. Based on theoretical model, it is predicted that shear wave is greater than longitudinal in the thermoelastic regime and longitudinal is greater than shear wave by reaction force in plasma regime. These predictions were verified through experiments by using of the XeF excimer pulsed laser of 480nm center-wavelength and the KrF excimer pulsed laser of 248nm. Also, for its directivity pattern, an arrival angle of the maximum longitudinal energy was around
and maximum shear energy was around
in the thermoelastic regime, and an arrival angle of maximum longitudinal energy was shown on nomal to the surface and maximum shear energy was represented in about
in plasma regime.
Optimum Pattern Synthesis for a Microphone Array
Chang, Byoung-Kun ; Kwon, Tae-Neung ; Byun, Youn-Shik ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 47~53
This paper concerns an efficient approach to forming a beam pattern of a microphone array to deal with broadband signals such as speech in a teleconference. A numerical method is proposed to find updated location of sidelobes for equalizaing the sidelobes via perturbation of array parameters such as array weight or microphone spacing. Thus the microphone array is optimized in a Dolph-Chebyshev sense such that directional or background noises incident in an array visual range are eliminated efficiently. It is shown that perturbation of microphone spacing yields an optimum pattern more appropriate for dealing with broadband signals than that of array weight. Also, a novel method is proposed to find a beam pattern which is robust with respect to sidelobe in a scanning situation. Computer simulation results are presented.
Shimmy Phenomena of Steering Wheel Due to the Tire Uniformity
Kim, Jong-Kwan ; Song, Sang-Kee ; Oh, Jin-Woo ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 54~59
The vehicle vibrations result from the exciting forces which are caused by air resistance, engine firing, tire mass unbalance and tire uniformity. Especially, the shake and shimmy phenomena in the steering system are closely related to the vehicle vibration, the tire unbalance, and the tire uniformity. This study presents the shimmy phenomena due to the tire mass unbalance and the tire uniformity in order to investigate their effects.
Two-Step Procedures for the Estimation of Two-Dimensional Distributed Sources
Lee, Seong-Ro ; Song, Ikck-Ho ; Lee, Joo-Shik ; Park, Jeong-Soon ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 60~66
Most research on the estimation of direction of arrival has been accomplished based on the assumption that the signal sources are point sources. In some real surroundings, signal source localization can more adequately be accomplished with distributed source models. When the signal sources are distributed over an area, we cannot directly use well-known DOA estimation methods, In this paper, we represent an source by the center angle and degree of dispersion. Then, we address the estimation of the elevation and azimuth angles of distributed sources based on the parametric distributed source modeling in the 3-dimensional space.
Analysis of Parameters for a RF Receiver System in the CMS
Chun, Jong-Hun ; Park, Jong-An ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 67~75
In this paper, A method is proposed to analyze the noise figure for some parameters based on IS-98 recommendation when a RF receiver for the CDMA mobile station is designed. Simulation results show that the maximum noise figure of the receiver, which fits in the receiving sensitivity of the mobile station, is about 11dB, and this value is smaller about 3dB than the existing specification. In addition, we have tested the relationship between frame error rate and Eb/Nt of traffic channel for each coding rate. according to the speed changes of the traffic channel. In order to prove IMD to be most important variable in LNA we have tested IMD spurious in case that LNA always turns on and in case that LNA turns ON/OFF.
Acoustic resonance and refrigerating capability of a Hofler type thermoacoustic refrigerating system
Hah, Zae-Gyoo ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 76~80
Acoustic resonance characteristics were analyzed and their effect on the refrigerating capability were experimentally verified on a fabricated Hofler-type thermoacoustic refrigerating system. Factors governing the overall resonance are the resonator composed of a cavity and two pipes, the loudspeaker driving the resonator, and rear side impedance characteristics of speaker housing. All these are coupled with electric constants of the speaker to exhibit electric resonance. Also the 'wall-effect' within the resonator causes attenuation to reduce the sharpness of the resonance. Analysis and experiments showed housing and the wall-effect of the resonator reduce the sharpness of resonance. Maintaining the accuracy of the resonance is, therefore, very important for efficient refrigeration.
The Recognition of Korean Single vowels by Use of the Diffusion Filter Bank as a Pre-processor
Huh, Man-Tak ; Kim, Jae-Chang ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 81~87
In this paper, a new pre-processing method for the recognition of single vowels by use of spectrum envelope is presented. We use new extraction method of a spectrum envelope using the diffusion filter bank. By dividing analysis band of a diffusion filter bank into subbands, we decreased the number of diffusion process. And, by increasing the number of difference, we got higher selectivity. As a result of them, we reduced the total processing time, and got higher enhancement of discrimination. By getting 88.3% of average recognition rate for single vowels of natural voice through computer simulation. We confirmed it to be useful for speech recognition which use spectrum analysis of the voice signal to have many frequency components.
Channel Allocation Scheme for Microcell Systems
Lee, Jong-Chan ; Mun, Young-Song ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 88~95
PCS(Personal Communications Systems) where the cell structure is microcell can accommodate more subscribers than those of cellular systems where the cell structure is macrocell by reducing the cell radius. To cope with such differences in PCS environment, new channel allocation schemes are needed. In this paper, problems which may arise when channel allocation scheme of cellular is applied to PCS is firstly analyzed. To overcome such problems, a new scheme is proposed. Performance of proposed schemes is analyzed and compared with other channel allocation schemes. Blocking probability is used as the performance parameter.
Implementation of A Fast Preprocessor for Isolated Word Recognition
Ahn, Young-Mok ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 96~99
This paper proposes a very fast preprocessor for isolated word recognition. The proposed preprocessor has a small computational cost for extracting candidate words. In the preprocessor, we used a feature sorting algorithm instead of vector quantization to reduce the computational cost. In order to show the effectiveness of our preprocessor, we compared it to a speech recognition system based on semi-continuous hidden Markov Model and a VQ-based preprocessor by computing their recognition performances of a speaker independent isolated word recognition. For the experiments, we used the speech database consisting of 244 words which were uttered by 40 male speakers. The set of speech data uttered by 20 male speakers was used for training, and the other set for testing. As the results, the accuracy of the proposed preprocessor was 99.9% with 90% reduction rate for the speech database.
Analysis of the Time Delayed Effect for Speech Feature
Ahn, Young-Mok ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 100~103
In this paper, we analyze the time delayed effect of speech feature. Here, the time delayed effect means that the current feature vector of speech is under the influence of the previous feature vectors. In this paper, we use a set of LPC driven cepstal coefficients and evaluate the time delayed effect of cepstrum with the performance of the speech recognition system. For the experiments, we used the speech database consisting of 22 words which uttered by 50 male speakers. The speech database uttered by 25 male speakers was used for training, and the other set was used for testing. The experimental results show that the time delayed effect is large in the lower orders of feature vector but small in the higher orders.
Derivation of MCE/GPD Training Algorithm Applicable to Weighted Hidden Markov Models
Choi, Hong-Sub ;
The Journal of the Acoustical Society of Korea, volume 16, issue 1, 1997, Pages 104~109
This paper derives a new training alorithm for WHMM using the well-known MCE/GPD method with experimental results on the E-set. The derived algorithm generalizes the conventional adaptive training algorithm for WHMM, which means that HMMs of multiple competing classes can be trained at the same time. The recognition results on the E-set have shown about 15% and 12% improvement for training and test data, respectively.