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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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Development and Evaluation of an Address Input System Employing Speech Recognition
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 3~10
This paper describes the development and evaluation of a Korean address input system employing automatic speech recognition technique as user interface for input Korean address. Address consists of cities, provinces and counties. The system works on a window 95 environment of personal computer with built-in soundcard. In the speech recognition part, the Continuous density Hidden Markov Model(CHMM) for making phoneme like units(PLUs) and One Pass Dynamic Programming(OPDP) algorithm is used for recognition. For address recognition, Finite State Automata(FSA) suitable for Korean address structure is constructed. To achieve an acceptable performance against the variation of speakers, microphones, and environmental noises, Maximum a posteriori(MAP) estimation is implemented in adaptation. And to improve the recognition speed, fast search method using variable pruning threshold is newly proposed. In the evaluation tests conducted for the 100 connected words uttered by 3 males the system showed above average 96.0% of recognition accuracy for connected words after adaption and recognition speed within 2 seconds, showing the effectiveness of the system.
New Acoustic Imaging Method Development for Localization of an Underground Acoustic Source Using a Passive SONAR System
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 10~10
The aim of the work described in this paper is to develop a complex underground acoustic system which detects and localizes the origin of an underground hammering sound using an array of hydrophones located about 100m underground. Three different methods for the sound localization will be presented, a time-delay method, a power-attenuation method and a hybrid method. In the time-delay method, the cross correlation of the signals received from the array of sensors is used to calculate the time delays between those signals. In the power-attenuation method, the powers of the received signals provide a measure of the distances of the source from the sensors. In the hybrid method, both informations of time-delays and power-ratios are coupled together to produce better performance of position estimation. A new acoustic imaging technique has been developed for improving the hybrid method. This new acoustic imaging method shows the multi-dimensional distribution of the normalized cost function, so as to indicate the trend of the minimizing direction toward the source location. For each method the sound localization is carried out in three dimensions underground. The distance between the true and estimated origins of the source is 28m for a search area of radius 250m.
Isolated Digit and Command Recognition in Car Environment
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 11~17
This paper proposes an observation probability smoothing technique for the robustness of a discrete hidden Markov(DHMM) model based speech recognizer. Also, an appropriate noise robust processing in car environment is suggested from experimental results. The noisy speech is often mislabeled during the vector quantization process. To reduce the effects of such mislabelings, the proposed technique increases the observation probability of similar codewords. For the noise robust processing in car environment, the liftering on the distance measure of feature vectors, the high pass filtering, and the spectral subtraction methods are examined. Recognition experiments on the 14-isolated words consists of the Korean digits and command words were performed. The database was recorded in a stopping car and a running car environments. The recognition rates of the baseline recognizer were 97.4% in a stopping situation and 59.1% in a running situation. Using the proposed observation probability smoothing technique, the liftering, the high pass filtering, and the spectral subtraction the recognition rates were enhanced to 98.3% in a stopping situation and to 88.6% in a running situation.
Fabrication of an Ultrasonic Speaker with Piezoelectric Ceramics
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 18~24
In this paper, we have investigated on the development of ultrasonic speakers that have higher directivity and much wider bandwidth than those of conventional loudspeakers. For optimal structure of speaker, we have analyzed material properties and dimension of the piezoelectric element and the vibrating metal plate, and their support type as well as the housing case. Based on the design, we have fabricated ultrasonic speaker prototypes, measured their performance, and verified validity of the design theory. For higher sound pressure level, the ultrasonic array speaker prototype has been fabricated in the form of an array. The design and fabrication method worked in this paper can be utilized in development of various ultrasonic speakers with higher directivity and broader bandwidth.
Improved Excitation Modeling for Low-Rate CELP Speech Coding
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 24~24
In this paper, we propose a weighting dependent mixed source model (WD-MSM) coder that is an improved version of a CELP-based mixed source model (C-MSM) coder. The coder classifies speech segments into three types : voiced, unvoiced and mixed. The excitation for a voiced frame is an adaptive source, and the excitation for an unvoiced frame is a stochastic source. The coder has a modified mixed source for a mixed frame. We apply different weighting functions for three classes. Simulation results show that the proposed coder at 4 kbits/s yields very good performance both subjectively and objectively.
Array Aperture Synthesis Technique with Improved Angle Resolution in Underwater Environment
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 25~31
An array aperture synthesis technique is proposed. The proposed method does not require the condition that the overlapped hydrophones have the identical position in space to estimate the phase correction factors. while the existing ETAM algorithm does. Therefore the proposed method increases the available data applied to extend the effective aperture length of the towed array. From the numerical experiments, the proposed method can reduce the mean square error in estimating the direction of a target signal.
On Formant Extraction Based on Transfer Function
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 31~31
This paper focuses on extracting formants from transfer function, derived from linear prediction analysis of speech signal. The second derivative of the log magnitude spectrum of the transfer function, the first and third derivatives of the phase spectrum of the transfer function in the z-plane are discussed. Their resolutions of detecting formants are analyzed and some comparisons are given. Theoretical analyses and experimental results show that the third derivative of the phase spectrum decays more rapidly around the formant locations than the first derivative of the phase spectrum and the second derivative of the log magnitude spectrum. Compared with the second derivative of the log spectrum and the first derivative of the phase spectrum, the third derivative of the phase spectrum has higher resolution in frequency domain and provides more accurate formant extraction.
High Frequency Vibration Analysis of Arrayed Panel Structures Using a Ray Tracing Method
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 32~39
In this paper, the characteristics of the ray tracing method (RTM) based on the cylindrical wave are discussed for the high frequency vibration analysis of two-dimensional structures. A ray tube describing the emanating cylindrical wave is used to derive the governing equation for incident reflected, and transmitted ray tubes which satisfies the condition at the coupled boundary. The suggested ray model is applied to panel array structures, and the predicted results for 2-panel, 3-panel, and 4-panel array structures are compared to those by Statistical energy analysis (SEA) and Wave intensity analysis(WIA). More enhanced prediction was obtained compared to the SEA, and similar prediction performance was observed to the WIA. Additionally, the RTM has a novel feature that it can estimate the spatially smoothed distribution of vibration energy and vibration intensity. It is expected that the present RTM can be used as one of the useful tools for the high frequency vibration analysis of two-dimensional coupled structures.
Estimation and Extraction of Unstable Frequency Lines of Acoustic Signal Using Neural Network
하석원 ; 황수복 ; 김재창 ;
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 39~39
In passive sonar, underwater moving objects are identified by the acoustic sounds they transmit. The spectrum of these sounds show features about the mechanism of the sound source, these features are discrete frequencies on the spectrum and frequency lines on the spectrogram. Variability in the underwater environment produce discontinuous broken or unstable fluctuating frequency lines. In this paper, we propose an efficient algorithm that estimate continuities of the discontinuous frequency lines and extract presence of the unstable frequency lines using neural networks and represent the proposed algorithm shows good performance in estimation and extraction the unstable frequency lines through the experiments.
A Study of Sidelobe Reduction Based on FFT in Ultrasound Images
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 40~47
Focusing is widely used to increase the resolution in ultrasound transmit field. It increases signal levels returning from the mainlobe direction and decreases those due to sidelobe directions. However, when the sidelobes cannot be completely canceled, the resulting image resolution is greatly deteriorated. This paper proposes a method of improving the resolution by scaling the received signal according to the difference between the mainlobe and sidelobe levels computed in the frequency domain by the use of Fourier transform. The proposed method is verified by computer simulation and experiments, and is shown to be highly effective in narrowing the mainlobe width and decreasing the sidelobe levels.
A Study on the Design of Integrated Speech Enhancement System for Hands-Free Mobile Radiotelephony in a Car
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 45~45
This paper presents the integrated speech enhancement system for hands-free mobile communication. The proposed integrated system incorporates both acoustic echo cancellation and engine noise reduction device to provide signal enhancement of desired speech signal from the echoed plus noisy environments. To implement the system, a delayless subband adaptive structure is used for acoustic echo cancellation operation. The NLMS based adaptive noise canceller then applied to the residual echo removed noisy signal to achieve the selective engine noise attenuation in dominant frequency component. Two sets of computer simulations are conducted to demonstrate the effectiveness of the system; one for the fixed acoustical environment condition, the other for the robustness of the system in which, more realistic situation, the acoustic transmission environment change. Simulation results confirm the system performance of 20-25dB ERLE in acoustic echo cancellation and 9-19 dB engine noise attenuation in dominant frequency component for both cases.
Voice Command Web Browser Using Variable Vocabulary Word Recognizer
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 48~52
In this paper, we describe a Voice Command Web Browser using a variable vocabulary word recognizer that can do Internet surfing with Korean speech recognition on the Web. The feature of this browser is that it can handle the links and menus of the web browser by speech. Therefore, we can use speech interface together with mouse for web browsing. To recognize the recognition candidates dynamically changing according to Web pages, we use the variable vocabulary word recognizer. The recognizer was trained using POW (Phonetically Optimized Words) 3,848 words. So that it can recognize new words which did not exist in training data. The preliminary test results showed that the performance of speaker-independent and vocabulary-independent recognition is 93.8% for 32 Korean words. The Voice Command Web Browser was developed on windows 95/NT using Netscape Navigator and reflected usability test results in order to offer easy interface to users unfamiliar with speech interface. In on-line experiment of speaker-independent and environment-independent situation, Voice Command Web Browser showed recognition accuracy of 90%.
A New Architecture of CMOS Current-Mode Analog-to-Digital Converter Using a 1.5-Bit Bit Cell
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 53~60
In this paper, it is proposed to a new architecture of CMOS IADC(Current-Mode Analog-to-Digital Converter) using 1.5-bit bit cell of which consists a CSH(Current-Mode Sample-and-Hold) and CCMP(Current-Mode Comparator). In order to guarantee the entire linearity of IADC, the CSH is designed to cancel CFT(Clock Feedthrough) whose resolution is to meet at the least 9-bit which is placed in the front-end of each bit cell. In the proposed IADC, digital correction logic is simplified and power consumption is reduced because bit cell of each stage needs two latch CCMP. Also, it is available for a mixed-mode integrated circuit because all of block is designed with only MOS transistor. With the HYUNDAI 0.8㎛ CMOS parameter, the HSPICE simulation results show that the proposed IADC can be operated at 20Ms/s with SNR of 43 dB with which is satisfied 7-bit resolution for input signal at 100 ㎑, and its power consumption is 27㎽.
A Sufficient Condition on the Stability of Recursive Discrete-Time Third-Order Volterra Filters
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 61~65
This paper derives a sufficient condition on the stability of recursive third-order Volterra filters based on their filter coefficients. A Volterra filter is very effective in modeling nonlinear systems with memory. However, it is well-known that the nonrecursive Volterra filter requires a large number of filter coefficients to describe a nonlinear system. For this reason, recursive Volterra filters are usually considered because the recursive implementation requires a smaller number of coefficients compared to the nonrecursive one. Unfortunately, the main problem of the recursive Volterra filters is their inherent instablility. In this paper. we present a simple condition for the output of a recursive discrete-time third-order Volterra filter to be bounded whenever the input signal to the recursive Volterra filter is bounded by a finite constant.
Development of a Correspondence Point Selection Algorithm for Visual Servo Control
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 66~76
This paper proposes that can take at high speed the information of binocular disparity with moving translational and forward stereo camera to the extent that does not occur the problem of a correspondence point. It shows that in case of stereo vision with translational motion, can take the information of binocular disparity being devoid of error and putting high confidence in, and that in case of stereo vision with forward motion, can take the horizontal component which can not be detected in common stereo vision. Besides, the stereo vision can be done at high speed due to being bright and small a correspondence point comparing not to do, because a correspondence between right and left images is previously limited. But there are problem that a resonable information of binocular disparity can not be taken, if the vicinity of center of image is in accord with the region of occlusion in stereo vision with forward motion.
Analysis and Synthesis of Audio Signals using a Sinusoidal Model with Psychoacoustic Criteria
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 77~82
A sinusoidal model has been widely used in the analysis and synthesis of speech and audio signals, and becomes one of the efficient candidates for high quality low bit rate audio coders. One of the crucial steps in the analysis and synthesis using a sinusoidal model is the detection of tonal components. This paper proposes an efficient method for the analysis and synthesis of audio signals using a sinusoidal model, which uses psychoacoustic criteria such as masking effect, masking index, and JNDf(Just Noticeable Difference in Frequency). Simulation results show that the proposed method reduces the number of sinusoids significantly without degrading the quality of the synthesized audio signals.
Wave Interpretation of Forced Vibration of Finite Cylindrical Shells
The Journal of the Acoustical Society of Korea, volume 18, issue 2, 1999, Pages 83~89
The forced vibration of a finite cylindrical shell has been analyzed from an elastic wave viewpoint. The displacement vector is used to formulate the vibration field, that is regarded as a superposition of disturbances due to elastic waves propagating on the shell. The reflection matrix is also used in the formulation of the vibration field, that is easily derived in the present approach. It allows one to easily identify the wave conversion of elastic waves at the ends of the shell. The present approach is used to predict the vibration field of the cylindrical shell with free-free boundary conditions. The contribution of each type of elastic waves into the vibration field was identified, and the wave conversion at the ends of the shell was observed. Those results showed that the present approach can be effectively used to analyze the forced vibration of the cylindrical shell from an elastic wave viewpoint.