• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.11
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• pp.93-100
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• 2005

In this paper, we implement the embedded speech recognition system to support various application services such as audio and video control using speech recognition interface on cars. The embedded speech recognition system is implemented and ported in a DSP board. Because MIC type and speech codecs affect the accuracy of speech recognition. And also, we optimize the simulation and test environment to effectively remove the real noises on a car. We applied a noise suppression and feature compensation algorithm to increase an accuracy of sppech recognition on a car. And we used a context dependent tied-mixture acoustic modeling. The performance evaluation showed high accuracy of proposed system in office environment and even real car environment.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.1
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• pp.45-53
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• 2020

Analytical and experimental studies show that the dynamic behavior of liquid storage tanks is significantly influenced by the fluid-structure interaction (FSI). The effects of FSI must be rigorously considered for accurate earthquake analysis and seismic design of liquid storage tanks. In this study, a dynamic analysis of a rectangular liquid storage tank subjected to bi-directional earthquake ground motions is performed and its dynamic characteristics are examined, with the effects of FSI rigorously considered. Hydrodynamic pressure is evaluated using the finite-element approach with acoustic elements and applied to the structure. The responses of the rectangular tank subjected to bi-directional earthquake ground motions are thus obtained. It can be observed that the incident angle of bi-directional horizontal ground motions has significant effects on the dynamic responses of the considered system. Therefore, the characteristics of the system must be considered in its seismic design and performance evaluation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.89-96
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• 2016

TDOA(time delay of arrival) position estimate from acoustic measurement of artillery shell impact is studied in order to develop a targeting evaluation system. Impact position is calculated from the intersections of hyperbolic estimates based on the least square Taylor series method. The mathematical process of Taylor series estimation is known to be robust. However, the concern lays with the accuracy because it is sensitive to the bias caused by the randomness of measurement situation. The measurement error typically occurs from the distortion of waveform, change of travelling path, and sensor position error. For outdoor measurement, a consideration should be made on the atmospheric condition such as temperature and wind which can possibly change the trajectories of rays of sound. It produces wrong propagation time events accordingly. Ray tracing and optimization techniques are introduced in this study to minimize the bias induced by the ray of sound. The numerical simulation shows that the atmospheric correction improves the estimation accuracy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.447-452
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• 2012

Among the various elements affecting a customer's evaluation of automobile quality, buzz, squeak and rattle (BSR) are considered to be major factors. In most vehicle manufacturers, the BSR problems are solved by find-fix method with the vehicle road test, mainly due to various excitation sources, complex generation mechanism and subjective response. The aim of this paper is to develop the integrated experimental method to systematically tackle the BSR problems in early stage of the vehicle development cycle by resolving these difficulties. To achieve this aim, the developed experimental method ought to include the following requirements: to find and fix the BSR problem for modules instead of a full vehicle in order to tackle the problem in the early stage of the vehicle development cycle; to develop the exciter system including the zig and road-input-signal reproducing algorithm; to automatically localize the source region of BSR; to develop sound quality index that can be used to assess the subjective responses to BSR. Also, the BSR sound quality indexes based on the Zwicker's sound quality parameters using a multiple regression analysis. The four sound metrics from Zwicker's sound quality parameter are computed for the signals recorded for eight BSR noise source regions localized by using the acoustic-field visualized results. Then, the jury test of BSR noise are performed for participants. On a basis of the computed sound metrics and jury test result, sound quality index is developed to represent the harsh of BSR noise. It is expected that the developed BSR detection system and sound quality indexes can be used to reduce the automotive interior BSR noise in terms of subjective levels as well as objective levels.

• Composites Research
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• v.15 no.1
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• pp.53-60
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• 2002

Composite ablative tubes required capabilities of ablative and structural characteristics were fabricated through filament winding technique and several experiments were conducted to evaluate the structural performance of composite ablative tubes. For this purpose, manufacturing procedures were briefly described and then resin digestion method was applied to measure the fiber volume fraction and the void content of composite ablative tubes. The configuration of tensile specimen fur composite ablative tubes with not losing the continuity of reinforced fibers was suggested by evaluating mechanical properties of several types of the specimen with different widths. Also, suitable processing variables for composite ablative tubes were determined by evaluating mechanical properties of several types of the specimen with different processing variables. In addition, acoustic emission signals were obtained during the proof test and could be applicable to study the crack initiation and the damage mode of composite ablative tubes. Finally, the structural reliability of composite ablative tubes could be verified to satisfy design requirements through the proof and burst tests.

• Investigative Magnetic Resonance Imaging
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• v.17 no.1
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• pp.59-62
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• 2013

There are various types of foreign body reactions, such as inflammation, edema, fluid collection, hematoma, infection, abscess and granulomas. There are various imaging findings according to types of foreign bodies and depending on the lapse of time. Therefore, correct diagnosis of a foreign body reaction is difficult and easily confused with soft tissue neoplasm. The MRI is ideal for the detection of foreign bodies regardless of radiolucency or acoustic impedance. It is especially very useful in the evaluation of the surrounding tissue reaction. The authors report a case of a 26-year-old female patient with both forearm swelling due to self-injection of a mixture of powdered tablets and saline. The lesion shows numerous internal T1 and T2 dark signal intensity micro-spots with surrounding fluid collection, which are diagnosed as foreign bodies with surrounding inflammatory changes during an operation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.5
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• pp.765-771
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• 2001

Elastic-plastic fracture toughness JIC can be used a s an effective design criterion in elastic-plastic fracture mechanics. Among the JIC test methods approved by ASTM, unloading compliance method was used in this study. In order to examine the relationship between fracture behavior of JIC test and AE signals, the post processing of AE signals has been carried out by Short Time Fourier Transform(STFT), one of the time-frequency analysis methods. The objective of this study is to evaluate the application of characterization of AE signals for unloading compliance method of JIC test. As a result of time-frequency analysis, we could extract the AE from the raw signal and analyze the frequencies in AE signal at the same time. AE signal generated by elastic-plastic fracture of material has some different aspects at elastic and plastic ranges, or the first portion of crack growth by fracture. First of all, increased energy recorded and detected by using AE count method increase rapidly from the start of ductile fracture. The variation of main frequency range with time-frequency analysis method could be confirmed. We could know fracture behavior of interior material by examination AE characteristics generated in real-time when elastic-plastic fracture occurred in material under loading.

• Science of Emotion and Sensibility
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• v.3 no.2
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• pp.17-28
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• 2000

Psychoacoustic characteristics of automobile horns play significant role in resulting subjective evaluation and psychphysiological reactions. However, comparison and differentiation of physiological responses to commercially available horns is a complicated task due to the small contrast in technical features of horns and the influence of such processes as habituation on physiological outcome with the increased number of auditory stimulation trials. In a study on 10 college students, there was performed comparative analysis of reactivity of physiological responses mediated by central and autonomic nervous systems in order to identify the role of habituation on decrement of psychophysiological responsivity and assess the ability to differentiate subjectively most and least preferred, as well as most and least appropriate horns according to physiological manifestations. The EEG and autonomic responses to 7 automobile horns were analyzed during 3 blocks of trials, with varying order of stimuli and changed acoustic parameters of horns in each block. Thus, responses were analyzed for totally 21 trials of auditory stimulation. It was shown that electrodermal and cardiovascular responses have different reactivity patterns to repeated stimulation: skin conductance measures habituated, cardiac reactivity showed no signs of habituation, and the vascular response demonstrated sensitization. The temporal EEG exhibited marked habituation of fast beta band power, while alpha-blocking effect did not habituate during the course of experiment. Differentiation of physiological responses of most and least preferred and appropriate horns was possible in our study, however, some cardiovascular reactivity measures differentiated during the entire course of the experiment, while EEG and electrodermal parameters showed significant differences only during first block of trials, and were later affected by the habituation.

• Phonetics and Speech Sciences
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• v.3 no.3
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• pp.133-140
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• 2011

Muscle misuse dysphonia (MMD) is defined as a behavioral voice disorder resulting from inappropriate contractions of intrinsic and/or extrinsic laryngeal muscles. The purpose of this study was to investigate the effect of motor learning guided laryngeal motor control therapy (MLG-LMCT) which is designed to improve an existing LMT and further the effective voice treatment on people with muscle misuse dysphonia. Forty-six people with MMD (M:F=16:30) participated in this study. The voice samples of the participants were recorded to investigate the effect of MLG-LMCT before and after the voice therapy. Voice samples were analyzed via electro-glotto-graph (EGG). Contact quotient (CQ), speed quotient (SQ), and waveform were reported. In addition, perceptual and acoustical evaluation were conducted to determine the change of voice improvement after treatment. The experimenter massaged the tensioned muscles around the neck. In order to find more proper phonation the experimenter showed the subjects their EGG wave forms as to whether or not they are moving the vocal folds to the appropriate position. Therefore, the EGG wave forms were used as a type of visual feedback. With the wave form, the experimenter helped subjects move the vocal folds and laryngeal muscles to find more proper voice production. The sensory stimuli from the experimenter gradually faded out. A paired dependent t- test revealed that there was significant differences in CQ between pre- and post-therapy. Perceptually, overall, rough, breathy, strain, and transition were significantly reduced. Acoustically, there were significant differences in Fo, jitter, shimmer, and NHR. After using MLG-LMCT, most of the subjects showed improvements in voice quality. The results from this study led us to the following conclusions: Motor learning guided laryngeal motor control therapy (MLG-LMCT) has reduces muscle misuse dysphonia. These results may occur because a visual feedback from EGG wave form can maintain the effect of the muscle tension reduction from laryngeal manual therapy. In case of people with MMD who reduced muscle tension from the therapy (LMT) but, not appropriately manipulating the location of larynx or adducting the vocal folds, MLG-LMCT might be an alternative therapy approach.

• Journal of Korean Association for Spatial Structures
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• v.10 no.3
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• pp.75-80
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• 2010

The present study tried to provide useful data for the acoustic design of sound amplification system with measuring and analyzing subjective preference and intelligibility by varying the number of speakers and their directivity. The results suggest that the room absorption plays a key role in subjective responses of listeners and the large sound absorption of ceiling contributes to the increase of intelligibility. Also, larger number of speakers with narrow directivity improves perceived intelligibility when speakers were installed at the lower height. However, the highest degree of intelligibility and preference were obtained when speakers were installed close enough to the sound absorptive ceiling. The highest intelligibility and preference were observed when 8 to 10 speakers with the directivity of 60 degree were used.