• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.711-714
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• 2000

In this study, the physical properties of the acoustic element and case with metal-piezoelectric ceramics were analyzed. The dielectric and piezoelectric properties of 0.5 wt% MnO$_2$and NiO doped 0.1Pb(Mg$\_$1/3Nb$\_$2/3)O$_3$-0.45PbTiO$_3$-0.45PbZrO$_3$ceramics were investigated aiming at acoustic transducer applications. The vibration characteristics for the laminated circular plate was analyzed for the various thickness and diameter of the piezoceramic layer and metal layer. Also, the acoustic characteristics for the geometrical form of case have been investigated. The design and fabrication method worked in this paper can be utilized in development of actuator and acoustic device.

• 음성과학
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• 제7권2호
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• pp.139-155
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• 2000

The aim of this research is to investigate acoustic characteristics of three different types of Korean Stops-plain, tensed, and aspirated-, and employ these as a base to determine which one(s) can be used as perceptual cues. In this paper, we have examined acoustic characteristics of Korean Stops, especially voice onset time(VOT), closure duration(CD), degree of pitch of following vowels and differences in the intensity of the Stops build-up after the onset of voicing. From the above characteristics, differences can be made between word-initial and word-medial positions. That is to say, in word-initial position, the three Korean Stops are distinguished by VOT and pitch, whereas in word-medial by CD, VOT and pitch. However, the acoustic characteristics do not have the same value as perceptual cues. In both word-initial, and medial positions, the immediately following vowels play the most important role in perceiving Korean Stops. And in case of word'-medial positions,. CD and VOT also play important perceptual roles. In order to have a more fine-grained distinction among Korean Stops, we think future research should be done to investigate which factor(s) of the following vowels is/are the most determinative perceptual cue(s). However, based on our investigation, we may conclude that it is highly plausible that pitch can be one of the most important perceptual cues when distinguishing the three Korean Stops.

• 교육시설
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• 제10권4호
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• pp.5-20
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• 2003

The purpose of the research on the noise of educational facilities is to build up pleasant environments by minimizing the influence on the students in the school. This study provides fundamental data for acoustic design by measuring, computer simulation and analyzing the room acoustic characteristics of the lecture room in middle school. For measurement on the factors of room acoustic, RT of lecture room and noise reductions depending on various walls of different structures were measured and analyzed. The lecture system being installed and carried out on the normal lecture room was divided into 4 types-employment of multimedia machines, employment of multimedia machines and loud speakers, employment of loud speaker, and existing verbal speaking-and SPL for each type was measured and analyzed. Based on the measured characteristics of acoustic characteristics for normal lecture room, the problems for environment of noise were understood through computer simulation, applications for improvements of performance for each facility were studied, schemes for improvements of performance by using the effects were presented, necessary fundamental data were secured, and schemes to enhance flexibility on the existing facilities of school against changing educational courses were secured.

• 말소리와 음성과학
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• 제5권3호
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• pp.55-60
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• 2013

The purpose of this study was to investigate the acoustic characteristics of crying infants according to the communication intents such as hunger and pain in terms of acoustic differences in the fundamental frequency ($F_0$), jitter, shimmer, noise-to-harmonic ratio(NHR), habitual pitch, and intensity. The subjects were 20 healthy, normal infants, less than seven days old, from the city of Seoul and were born after 38 to 42 weeks(full term) of pregnancy. The sound of crying was recorded for three minutes. The crying due to pain was induced by means of the inborn metabolism error test, whereas the crying due to hunger was verified by means of the rooting reflex by waiting for the designated eating time. The results were as follows: (1) the fundamental frequency, noise-to-harmonic ratio(NHR), and intensity of the infants' crying due to pain was higher than that by hunger, showing a significant difference between the mean values. (2) the infants' crying due to hunger and that by pain did not have a significant difference in the mean jitter and shimmer values but both of them were largely outside of the normal threshold values(jitter by 1.04% and shimmer by 3.81%). This study was significant in the sense that it showed the acoustic characteristics of infants' crying from hunger and pain were very different from each other according to the communication intents in terms of the six acoustic parameters.

• 한국소음진동공학회논문집
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• 제26권1호
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• pp.5-12
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• 2016

This paper describes the development process for vibration and acoustic characteristics of a balanced armature speaker. The design parameters were chosen in consideration of the influence of the bending stiffness of balanced armature which is the form of a cantilever structure in the speaker. For study of the performance of the speaker according to the design parameters, in the first step, we analyzed the characteristics of the velocity of the diaphragm to the electrical input. Next step, acoustic characteristics were analyzed by structural-acoustic coupled analysis. And the reliability of the analysis was verified by comparing the result of analysis with test results. Finally, we proposed a design method for implementing an enhanced balanced armature speakers through analysis method.

• 한국추진공학회지
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• 제21권6호
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• pp.103-109
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• 2017

연소화염 열에너지와 결합된 음향에너지 증가는 연소 불안정성을 유발할 수 있다. 연소 안정성 예측을 위해서는 연소실 내부 유동 경계에서 음향특성을 파악해서 궁극적으로 음향에너지의 증가 여부를 파악하는 것이 필요하다. 본 논문에서는 연소기 헤드와 같은 유동 경계 형상에 대한 음향 특성을 연구한 기존의 주요 분석적 결과를 정리하여, Strouhal 수로 표현되는 경계면 음향 임피던스 특성을 알아보았다. 또한 이중 마이크로폰을 활용한 실험적 방법을 통해 경계 음향 임피던스 특성에 대한 이론적/해석적 결과를 검증하기 위한 기법을 조사 정리하였다.

• 한국소음진동공학회논문집
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• 제22권5호
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• pp.429-436
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• 2012

In concert halls and auditoriums, acoustic reflector and stage enclosure is one of the main factors on the room and stage acoustic characteristics. As a stage enclosure and acoustic reflector honey comb based light-weight reflector is widely used, because it is easy to install. However, there was not enough research on the surface density effect on room and stage acoustics. In this study, sound absorption coefficient tests on three kinds of wooden acoustic reflectors with different surface density were conducted. Surface density of acoustic reflector was changed from 11 kg/$m^2$ to 41 kg/$m^2$. For the low frequency excitation, sub-woofer was used with omnidirectional loud-speaker simultaneously. From the experiments, it was found that sound absorption coefficient below 250 Hz band was decrease by the increment of surface density. In order to check the influence of the surface density on room and stage acoustic parameters, room acoustic simulation was conducted with sound absorption coefficients, which were tested in reverberation chamber. By the increment of surface density of acoustic reflector, RT(reverberation time) and EDT(early decay time) were increased. Also, ST(stage support) was improved in low frequency bands.

• 말소리와 음성과학
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• 제6권2호
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• pp.115-121
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• 2014

This paper investigates the relationship between acoustic characteristics and voice handicap index for 29 males with esophageal speakers. Acoustic characteristics were measured by using a sustained vowel /a/ three times. The stable vocalization for 2 seconds was analyzed by MDVP program. Specifically, relationships between four VHI scores (total, functional, physical, and emotional) and three acoustic characteristics (jitter, shimmer, and NHR) were investigated using the Pearson correlation coefficient. As results, we found no relationship between NHR and VHI scores. However, both jitter and shimmer had statistically significant correlations with all four VHI scores. This research will contribute to establishing a baseline related to speech characteristics in voice rehabilitation with esophageal speakers. Further research could be done to examine the overall quality of life survey, which is widely used as a subjective measure about voice for patients with esophageal speakers.

• 한국컴퓨터정보학회논문지
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• 제12권3호
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• pp.259-266
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• 2007

소형 마이크로폰의 성능을 평가하는 기준으로 사용되는 전기 음향 특성 파라메타들로는 감도, 왜곡, 주파수 응답특성, 그리고 지향성이 있다. 이와 같은 특성 파라메타들은 소형 마이크로폰의 사용 목적에 따라 다르게 설계되어야하므로, 음향특성들을 정확하게 측정하여 소형 마이크로폰이 사용 목적에 적합하게 만들어 졌는지를 측정하여 확인하여야 한다. 따라서, 본 논문에서는 DSP를 이용하여 소형 마이크로폰의 음향특성 파라메타들을 동시에 측정할 수 있고, 또한 실시간에 측정할 수 있는 시스템을 구현하였다. 구현한 측정 시스템을 검증하기 위하여 네 종류의 마이크로폰의 음향특성들을 측정하고, 각 마이크로폰이 갖고 있던 음향특성 데이터 값들과 비교한 결과, 측정 환경이 동일하지 않아 비교 값들 간에 약간의 오차가 있었지만, 그 오차 값들이 허용오차의 범위 내에 분포하고 있음을 확인하였으므로 구현된 시스템이 기존의 소형 마이크로폰 음향특성 측정 장비를 대체하여 사용할 수 있음을 입증하였다.

• 한국음향학회:학술대회논문집
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• 한국음향학회 2000년도 하계학술발표대회 논문집 제19권 1호
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• pp.275-278
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• 2000

In this study, the acoustic transducer of a thin circular disc-type with PZT/Metal was designed. The dielectric and piezoelectric properties of $0.5wt\%$ $MnO_2$ and NiO doped 0.1Pb($Mg_{1/3}$$Nb_{2/3}$)$O_3$-$0.45PbTiO_3$-$0.45PbZrO_3$ ceramics were investigated aiming at acoustic transducer applications. The vibration characteristics for the laminated circular plate was analyzed for the various thickness and diameter of the piezoceramic layer and metal layer. The acoustic characteristics which is radiated from the acoustic transducer within the finite space was simulated using the finite element method. It has been observed that the characteristics of the sound pressure ard impedance response calculated for the various models of the size and geometry of acoustic transducer.