• 대한조선학회논문집
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• 제56권5호
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• pp.464-471
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• 2019

The acoustic power is a major acoustical characteristic of an underwater vehicle and could be measured in a reverberant water tank. In order to obtain accurate measurement results, the acoustic field formed by the sound source should be investigated quantitatively in the reverberant water tank. In this research, the acoustic field of a reverberant water tank containing an underwater sound source has been analyzed by using an acoustic radiosity method one of the numerical analysis methods suitable for the acoustic analysis of the highly diffused space. The source level of the underwater sound source and acoustical properties of the water tank input to the numerical analysis have been estimated by applying the reverberant tank plot method through a preliminary experiment result. The comparison of the numerical analysis result with that of the experiment has verified the accuracy of the acoustic radiosity method.

• Journal of Biosystems Engineering
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• 제34권4호
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• pp.260-268
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• 2009

As a basic study to develop a high sensitive biosensor using film bulk acoustic resonator, the mathematical model for analyzing the resonance characteristics of bulk acoustic resonator with acoustic Bragg reflectors was investigated. The simulation results due to the number of acoustic Bragg reflectors with low and high acoustic impedance materials were compared with the experimental results for 1, 2.25 and 5 MHz of PZT based bulk acoustic resonators with various acoustic Bragg reflectors. At the fabricated bulk acoustic resonator with an odd number of acoustic Bragg reflectors, low and high acoustic impedance materials in sequence under the bottom electrode showed better resonance characteristics than even number of acoustic Bragg reflectors. The changes of resonance frequencies due to the increase of number of acoustic Bragg reflectors by simulation and experiment, respectively showed approximately similar tendency but some differences in input impedance between the experiment and simulation were found. The derived mathematical model for describing the resonance characteristics of the bulk acoustic resonator with acoustic Bragg reflector will be available for analyzing the design parameters for development of biosensor using bulk acoustic resonator.

• 음성과학
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• 제12권3호
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• pp.185-200
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• 2005

The objective of this study is to examine acoustic cues in spoken French for the assessment of pronunciation which is necessary to realization of the multimedia system. The corpus is composed of simple expressions which consist of the French phonological system include all phonemes. This experiment was made on 4 male and female French native speakers and on 20 Korean speakers, university students who had learned the French language more than two years. We analyzed the recorded data by using spectrograph and measured comparative features by the numerical values. First of all, we found the mean and the deviation of all phonemes, and then chose features which had high error frequency and great differences between French and Korean pronunciations. The selected data were simplified and compared among them. After we judged whether the problems of pronunciation in each Korean speaker were either the utterance mistake or the interference of mother tongue, in terms of articulatory and auditory aspects, we tried to find acoustic features as simplified as possible. From this experiment, we could extract acoustic cues for the construction of the French pronunciation training system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.574-576
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• 2004

The directivity of the sound pressure increases the sensitivity of the incoming sound from specific directions. The directivity measurement of the sound pressure is usually done in an anechoic room using a sloping motor. In this paper a replaceable anechoic chamber was designed for the acoustic directivity pattern measurement. Electrical equipments were interfaced with a PC for experiment automatic control. Some comparative results are shown in the result.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.591-594
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• 2004

The directivity of the sound pressure increases the sensitivity of the incoming sound from specific directions. The directivity measurement of the sound pressure is usually done in an anechoic room using a steping motor. In this paper a replaceable anechoic chamber was designed for the acoustic directivity pattern measurement. Electrical equipments were interfaced with a PC for experiment automatic control. Some comparative results are shown in the result.

• 한국전기전자재료학회논문지
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• 제23권1호
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• pp.53-60
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• 2010

This paper dealt with the acoustic detection of partial discharge (PD) in insulation oil for insulation diagnostics of oil immersed transformers. Electrode systems such as needle to plane, plane to plane, and floating were fabricated to simulate some defects in transformers. A wide band acoustic emission(AE) sensor with the frequency ranges of 100 kHz~1 MHz and a narrow band AE sensor with the resonant frequency of 140 kHz were used in the experiment. Also, a decoupler and an amplifier were designed to detect and amplify the acoustic signal only. The decoupler separates acoustic signal from DC source without any distortion, and the amplifier has the gain of 40 dB in frequency ranges of 11 kHz~4 MHz. In the experiment, frequency components and propagation characteristics of acoustic signal were analyzed, and an algorithm of positioning of PD occurrence by the time difference of arrival was proposed. From the results, the frequency components of the acoustic signal exist from 50 kHz to 200 kHz and the positioning error of PD calculated by three AE sensors was within 1%.

• 말소리와 음성과학
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• 제10권3호
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• pp.41-48
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• 2018

This study examined the acoustic characteristics of Korean alveolar fricatives of normal children. Developing children aged 3 and 7, typically produced 2 types of nonsense syllables containing alveolar fricative /sV/ and /VsV/ sequences where V was any one of three corner vowels (/i, a, and u/). Stimuli containing the speech materials used in a production experiment were presented randomly to 12 speech language pathologists (SLPs) for a perception test. The SLPs responded by selecting one of seven alternative sounds. Acoustic measures such as duration of frication noise, normalized intensity, skewness, and center of gravity were examined. There was significant difference in acoustic measures when comparing vowels. Comparison of syllable structures indicated statistically significant differences in duration of frication noise and normalized intensity. Acoustic parameters could account for the perceptual data. Relating the acoustic and perception data by means of logistic regression suggests that duration of frication noise and normalized intensity are the primary cues to perceiving Korean fricatives.

• 한국음향학회지
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• 제37권6호
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• pp.451-456
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• 2018

최근 장거리 수중음향통신 연구가 활발하게 진행되고 있다. 장거리 수중음향통신 연구를 위한 해상실험은 해양환경의 영향을 크게 받고 높은 비용과 많은 시간이 소요된다. 따라서 장거리 환경에서 수중음향통신 시스템의 성능을 예측하고 검증하기 위한 시뮬레이터에 대한 연구가 필요하다. 본 논문에서는 장거리 수중음향통신 시뮬레이터의 개발을 목적으로 중장거리 다중송신환경에서 수중음향통신 시뮬레이터로서 VirTEX(Virtual Time series EXperiment)의 성능을 분석하고, 해상 실험 결과와 비교 검증하였다. 송신 신호는 탐침을 위한 Chirp신호와 16QAM 방식으로 변조된 통신 신호를 사용하였다. VirTEX를 통해 수신 신호를 모의하고 다중송신환경에 의해 발생하는 채널 간 간섭을 적응 수동형 시역전을 이용하여 보상하여 통신 성능을 분석하였다. 또한 2005년 7월 이탈리아의 Elba island 북쪽 해역에서 수행한 FAF05(Focused Acoustic Field 2005) 실험 데이터와 비교하여 이를 검증하였다.

• 자원환경지질
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• 제29권5호
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• pp.629-637
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• 1996

In this paper a numerical experiment is conducted to determine the low acoustic impedance of a thin oil or gas reservoir from a seismogram by using the generalized linear inversion method. The seismograms used are normal incident synthetic seismograms containing p-wave primary reflections, multiples, and peg-leg multiples on the layers consisting of oil-, gas-, water-filled sandstone incased in shales. In this experiment the acoustic impedance, the location of reservoir boundary, thickness, and source wavelet are assumed initially and revised iteratively by the least-squares-error technique until the difference between the seismogram and calculated one is very small. This experiment shows that the acoustic impedance and thickness, about 10 m thick, can be determined by the inversion.

• 한국음향학회지
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• 제12권3호
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• pp.43-48
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• 1993

This study was carried out to verificate the possibility of using the laboratory setting psycho-acoustic experiment compared with the field and to delineate the appropriate indices in evaluating the Noisiness of road traffic noise by means of psycho-acoustic method. Reviewing the typical patterns of traffic noises depending upon the shapes ad conditions of the road, the road traffic noises in several representative points in the major residential areas in Kwangju city were recorded and reproduced with the noise levels modified in various steps. With these 20 sound sources, psycho-acoustic experiments in the laboratory were performed on 11 volunteer subjects. And then, psycho-acoustic experiments in the real field were performed on 10 volunteer subjects to compare the results of the laboratory experiment, the results are summerized as follows : 1. The psycho-acoustic experiments in the laboratory elicited the data well matching with those obtained in the field, resulting in even higher corelation levels. This indicates that the field assessement of responses to the noise can be replaced by the evaluatioin in the laboratory settings which render many variables easily controlled and that the responses of the residents to the noise can be easily predicted in the laboratory by applying this method. 2. Also among the complex indices, such as Noise Pollution Level or Annoyance Index high correlations were detected. On the other hand, low corelations were noted among Traffic Noise Index. 3. Highly significant correlations were found among the direct indices such as Leq, L\sub 10\, On the other hand, low correlations were detected among L\sub 50\.