• 대한음성학회지:말소리
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• 제67호
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• pp.1-16
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• 2008

Stress effects upon Korean vowels were investigated with reference to rhythm. We measured three acoustic correlates (Duration: VOT, Vowel Duration; F0; Intensity) of stress from the seven pairs of stressed vs. unstressed Korean vowels /i, ${\varepsilon}(e)$, a, o, u, i, e/. The results of the experiment revealed that stress gave only inconsistent and weak effects on duration, which supports that Korean is not a stress-timed language as far as strong stress effects on duration are still considered crucial in stress-timing. On the other hand, Korean stressed vowels were most characterized with higher F0 and next with stronger intensity. But speakers generally showed tactics to reversely use F0 and intensity in stressing an utterance rather than proportionately strengthening both of the two acoustic correlates of stress. There was found great inter-speaker variability especially in the variations of duration.

• 음성과학
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• 제8권1호
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• pp.7-19
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• 2001

The acoustic parameters of nine Korean numbers were analyzed by Praat, a speech analysis software, and synthesized by SenSynPPC, a Klatt formant synthesizer. The overall intensity, pitch and formant values of the numbers were modified dynamically by a step of 1 dB, 1 Hz and 2.5% respectively. The study explored the sensitivity of listeners to changes in the three acoustic parameters. Twelve subjects (male and female) listened to 390 pairs of synthesized numbers and judged whether the given pair sounded the same or different. Results showed that subjects perceived the same sound quality within the range of 6.6 dB of intensity variation, 10.5 Hz of pitch variation and 5.9% of the first three formant variations. The male and female groups showed almost the same perceptual ranges. Also, an asymmetrical structure of high and low boundary was observed. The ranges may be applicable to the development of a speaker identification system while the method of synthesis modification may apply to its evaluation data.

• 음성과학
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• 제10권1호
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• pp.3-13
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• 2003

The devoicing vowel is a phonological process whose contrast in sonority is lost or reduces in a particular phonetic environment. Phonetically, the vocal fold vibration originates from the abduction/adduction of the glottis in relation to supraglottal articulatory movements. The purpose of this study is to investigate Korean vowel devoicing by means of experimental instruments. The interrelated laryngeal adjustments and aerodynamic effects for this voicing can clarify the redundant articulatory gestures relevant to the distinctive feature of sonority. Five test words were selected, being composed of the high vowel /i/, between the fricative and strong aspirated or lenis affricated consonants. The subjects uttered the test words successively at a normal or at a faster speed. The EMG, the sensing tube Gaeltec S7b and the High-Speech Analysis system and MSL II were used in these studies. Acoustically, three different types of speech waveforms and spectrograms were classified, based on the voicing variation. The intraoral air pressure curves showed differences, depending on the voicing variations. The activity patterns of the PCA and the CT for devoicing vowels appeared differently from those showing the partially devoicing vowels and the voicing vowels.

• 대한음성학회:학술대회논문집
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• 대한음성학회 2002년도 11월 학술대회지
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• pp.41-44
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• 2002

This paper is related to the enhancement of speech recognition rate using enhanced pronunciation dictionary. Modern large vocabulary, continuous speech recognition systems have pronunciation dictionaries. A pronunciation dictionary provides pronunciation information for each word in the vocabulary in phonemic units, which are modeled in detail by the acoustic models. But in most speech recognition system based on Hidden Markov Model, actual pronunciation variations are disregarded. Without the pronunciation variations in the speech recognition system, the phonetic transcriptions in the dictionary do not match the actual occurrences in the database. In this paper, we proposed the unvoiced rule of semivowel in allophone rules to pronunciation dictionary. Experimental results on speech recognition system give higher performance than existing pronunciation dictionaries.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1037-1044
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• 2007

In an attempt to determine the correlations between the input acoustic impedance and the variations of the physical characteristics of the terminal elements, a five-lobe branched tube-network is mathematically developed and experimentally simulated using a lung simulator. The model takes into account some realistic conditions such as varying cross-sectional areas, flexible wall properties and branching. The effects of airway constrictions expressed by lobe stiffness variations on the impedance are determined for a range of frequencies up to 256 Hz. It is concluded that the developed model is capable of non-invasively predicting various physiological changes in the airway passages.

• 수산해양기술연구
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• 제32권4호
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• pp.395-401
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• 1996

In this paper, the propagation characteristics due to the horizontal water temperature variations in the sea such as thermal fronts is analyzed by the ray theory. Two models for the temperature anomaly layer are chosen. One is a plane type and the other is a cylindrical type. In the plane type, the temperature increases linearly from a isothermal region to 5km with the gradient of about $2^{\circ}C.$/km, and decreases with the same gradient in next 5km. In the cylindrical type, water temperature increases only with the same gradient from a half cylindrical thermal boundary surface. The result showed that the gradient of acoustic rays decreases in the temperature increasing region and vice versa in temperature decreasing region. And, the transmission loss due to the temperature variation was less than O.2dB in the plane type model as well as in the cylindrical one.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
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• pp.546-560
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• 2000

This paper describes the design and evaluation of a noise suppressing hydrophone that is robust to external noise without sacrificing its performance as a receiver. To increase robustness of the receiver to the external noise, first, effects of location of external noise on its performance are analyzed with the finite element method (FEM). Based on the results, geometrical variations are implemented on the structure with additional air pockets and damping layers that work as acoustic shields or scatterers of the noise, and fourteen trial models are developed for the noise suppressing hydrophone structures. The results show that the effect of the external noise is most significant when it is applied to near the mid-side surface of the hydrophone housing. The external noise is isolated most efficiently when two thin damping layers combined with five air pockets are inserted to the circumference of the hydrophone housing. Overall, of the fourteen structural variations of the hydrophone, the best one shows about 87% reduction in the response of the original structure to external noise.

• Ocean and Polar Research
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• 제29권2호
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• pp.113-121
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• 2007

The sound wave in the sea propagates under the effect of water depth, sound speed structure, sea surface roughness, bottom roughness, and acoustic properties of bottom sediment. In shallow water, the bottom sediments are distributed very variously with place and the sound speed structure varying with time and space. In order to investigate the seasonal propagation characteristics of low-frequency sound wave in the Yellow Sea, propagation experiments were conducted along a track in the middle part of the Yellow Sea in spring, summer, and autumn. In this paper we consider seasonal variations of the sound speed profile and propagation loss based on the measurement results. Also we quantitatively investigate variation of bottom loss by dividing the propagation loss into three components: spreading loss, absorption loss, and bottom loss. As a result, the propagation losses measured in summer were larger than the losses in spring and autumn, and the propagation losses measured in autumn were smaller than the losses in spring. The spreading loss and the absorption loss did not show seasonal variations, but the bottom loss showed seasonal variations. So it was thought that the seasonal variation of the propagation loss was due to the seasonal change of the bottom loss and the seasonal variation of the bottom loss was due to the change of the sound speed profile by season.

• 말소리와 음성과학
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• 제1권1호
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• pp.63-67
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• 2009

In this paper, in order to protect music copyrights, we propose a music identification system which is scalable to the number of pieces of registered music and robust to signal-level variations of registered music. For its implementation, we define the new concepts of 'music word' and 'music phoneme' as recognition units to construct 'music acoustic models'. Then, with these concepts, we apply the HMM-based framework used in continuous speech recognition to identify the music. Each music file is transformed to a sequence of 39-dimensional vectors. This sequence of vectors is represented as ordered states with Gaussian mixtures. These ordered states are trained using Baum-Welch re-estimation method. Music files with a suspicious copyright are also transformed to a sequence of vectors. Then, the most probable music file is identified using Viterbi algorithm through the music identification network. We implemented a music identification system for 1,000 MP3 music files and tested this system with variations in terms of MP3 bit rate and music speed rate. Our proposed music identification system demonstrates robust performance to signal variations. In addition, scalability of this system is independent of the number of registered music files, since our system is based on HMM method.

• 대한구순구개열학회:학술대회논문집
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• 대한구순구개열학회 2003년도 종합학술대회
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• pp.46-46
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• 2003