• 대한의용생체공학회:의공학회지
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• 제16권4호
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• pp.471-480
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• 1995

기니픽 고막에의 격음 노출 전후에 N1-N2 오디오그램의 변화를 검사하였다. 격음 노출은 106 dB SPL의 세기와 10KHz의 주파수를 가진 연속 격음을 10분 동안 노출시키는 방법이였다. 격음 노출 전후의 N1-N2 오디오그램들을 비교한 결과, 격음 노출된 달팽이관이 그의 기능을 영구적으로 상실하고 있음을 보여줬다. 가장 두드러진 한계치의 이동이 12-13.2KHz 사이에서 발생하였다. 격음 노출후의 달팽이관 기능의 변화는 격음 손상 이전의 달팽이관 상태에 따라 달라졌다. 좀 더 예민한 달팽이관이 덜 예민한 달팽이관 보다 격음 손상이후 그 기능면에서 더욱 심각하게 손상되었다.

• 음성과학
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• 제4권2호
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• pp.115-139
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• 1998

The aim of this study is to develop an the assessment program for the singing voice which is based on the physiological and acoustic methods. 22 sopranos, 6 mezzo sopranos, 4 tenors and 4 baritones participated to these experiments. The results measured by Visi-Pitch, spectrograph, and strobo-scope can be summarized as follows: (1) The maximum phonation time of singers must over 14 second higher with one deep inspiration (2) The parts classified by vocal range using Visi-Pitch: soprano between 167Hz $\sim$1,190Hz, mezzo soprano between 146Hz$\sim$956Hz, tenor between 75Hz$\sim$503Hz and baritone between 73 Hz and 385 Hz. (3) Longitudinal glottal size of singers decreases depending on the high-low pitch variation while lattitudinal glottal size increases depending on high-low pitch variation. (4) Well-trained singers show over 5 times the vibrato rate of untrained singers and regular pitch variation during measured periods. Vibrato's intensity do not over 3 dB. (5) Singer's formant indicates professional voice depending on the each parts: 3,207 Hz for soprano, 3,057 Hz for mezzo soprano, 2,754 Hz for tenor and 2,560 Hz for baritone.. (6) $F_1$ of singing voice is higher than that of speech while $F_2\;and\;F_3$ of singing voice are lower than those of speech.

• 음성과학
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• 제4권2호
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• pp.69-89
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• 1998

The aim of this study is to develop an objectively method of speech evaluation for children with cleft palates. To assess velopharyngeal function, Visi-Pitch, Computerized Speech Lab. (CSL), Nasometer and Palatometer were used for this study. Acoustic parameters were measured depending on the diagnostic instruments: Pitch (Hz), sound pressure level (dB), jitter (%) and diadochokinetic rate by Visi-Pitch, VOT and vowels formant ($F_1\;&\;F_2$) by a Spectrography and the degree of hypernasality by Nasometer. In addition, Palatometer was used to find the lingual-palatal patterns of cleft palate. Ten children with cleft palates and fifty normal children participated in the experiment. The results are as follows: (1) Higher nasalance of children with cleft palates showed the resonance disorder. (2) The cleft palate showed palatal misarticulation and lateral misarticulation on the palatogram. (3) Children with cleft palates showed the phonatory and respiratory problems. The duration of sustained vowels in children with cleft palates was shorter than in the control groups. The pitch of children with cleft palates was higher than in the control groups. However, intensity, jitter and diadochokinetic rate of children with cleft palates were lower than in the control group. (4) On the Spectrogram, the VOT of children with cleft palates was longer than control group. $F_1\;&\;F_2$ were lower than in the control group.

• 한국음향학회지
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• 제6권1호
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• pp.48-57
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• 1987

냉장고에 있어서 소음의 주발생원이 압축기라는 것은 잘 알려져 있는 사실이며 최근 제품의 경량화와 고급화 추세에 따라 그 영향이 더욱 증대되고 있다. 본 연구에서는 이러한 소음을 방지 또는 감소시키기 위하여 냉장고용 압축기에 대한 음압과 음향인텐시티를 측정하여 소음의 방사특성을 파악하였으며 이를 규명하기 위하여 실험적 모우드 해석법을 압축기 구조물에 대하여 적용하였다. 연구결과, 압축기 내부의 모우터 구동에 의해 발생한 진동이 스프링에 의해 효과적으로 절연되지 못하고 있으며 압축기의 shell과 mounting도 소음에 크게 기여하고 있음을 알았다.

• 음성과학
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• 제8권3호
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• pp.173-184
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• 2001

The purpose of this study was to examine the effects of manipulating loudness and pitch in terms of speech intelligibility and voice of a patient with Parkinson's Disease. The subject, who was diagnosed as a patient with Parkinson's disease 11 years ago, demonstrated a severely breath voice with low intensity. The accuracy of articulation in consonants was intelligible only at the single word level, and the overall intelligibility in continuous speech was low. The results showed that the subject's articulation accuracy and speech intelligibility was significantly improved after having loudness and pitch training. Habitual Fo, Jitter, Shimmer, Fo tremor, Amp tremor were decreased after training. In addition, the value of HNR also increased after training. It was shown that the changes of these acoustic parameters were closely related to the decrease of breathiness in Parkinson's voice, and this decrease of breathiness affected speech intelligibility considerably. Based on the experimental results, it was claimed that the vocal training by manipulating the loudness and pitch could be highly effective in improving the voice quality and speech intelligibility in Parkinson's Disease.

• 말소리와 음성과학
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• 제2권2호
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• pp.43-50
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• 2010

English vowels can be divided into monophthongs and diphthongs depending on the number of vocal tract shapes. Diphthongs are usually produced with more than one shape. This study attempts to collect acoustical data of English diphthongs published by Hillenbrand et al.(1995) online and to examine acoustic features of the diphthongs for phoneticians and English teachers. Sixty three American males and females were chosen after excluding those subjects with different target vowels or ambiguous formant tracks. The author used Praat to obtain the acoustical data systematically at eleven equidistant timepoints over the diphthongal segment. Obvious errors were corrected based on the spectrographic display of each diphthong. Results show that the formant trajectories of the diphthongs produced by the American males and females appeared quite similar. When the female formant values were uniformly normalized to those of the males, almost a perfect collapse occurred. Secondly, the diphthongal movements on the vowel space appeared not linear due to the coarticulatory gesture for the following consonant. Thirdly, the average duration of the diphthongs produced by the females was 1.156 times longer than that of the males while the pitch ratio between the two groups turned out to be 1.746 with a similar contour over measurement points. The author concludes that English diphthongs produced by various groups can be compared systematically when the acoustical values are obtained at proportional timepoints. Further studies will be desirable on the comparison of English diphthongs produced by native and nonnative speakers.

• 동력기계공학회지
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• 제18권6호
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• pp.166-173
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• 2014

In this study, a laminated composite material with dispersing aluminum oxide powder between the CFRP laminate plies, and also CFRP composites without aluminium oxide powder were fabricated for Mode I experiments using the DCB specimen and a tensile test. The behavior of the crack and the change of the interfacial fracture toughness were evaluated. Also in order to evaluate the damage mechanism for the crack extension, the AE sensor on the surface of the DCB test specimen was attached. AE amplitude was estimated for CFRP-alumina and CFRP composite. And the fracture toughness was evaluated by the stress intensity factor and energy release rate. The results showed that an unstable crack was propagated rapidly in CFRP composite specimen along with the interface, but crack propagation in CFRP-alumina specimen was relatively stable. From results, we show that aluminium oxide powder spreaded uniformly in the interface of the CFRP laminate carried out the role for preventing the sudden crack growth.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2019년도 학술발표회
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• pp.282-287
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• 2019

본 연구의 목적은 음파를 이용하는 유속계로부터 관측된 후방산란강도와 실측된 부유사농도의 상관관계를 해석하여, 두 인자 사이의 관련 매개변수를 정량적으로 산정하고 관계식을 도출하는데 있다. 이를 위해 층별 유속계인 Aquadopp Profiler를 사용하여 사질 퇴적물 및 고령토 부유퇴적물 관측센서 검보정 챔버 실험을 수행하였다. 두 인자의 상관관계는 선형회귀분석을 통해 해석하였으며 그 결과로 도출된 접합곡선의 기울기는 각각 안목 A1 이 2.065, 안목 A2가 1.576, 고령토시료일 때 2.588의 값을 갖는데 이러한 차이는 시료 특성으로 설명될 수 있다. 서로 다른 입경을 갖는 시료는 후방산란 민감도에 차이가 있으며 이러한 영향으로 두 시료에서 산정된 계수 값에 차이가 발생한다. 본 연구를 통하여 도출된 측정 결과들은 후방산란강도에 미치는 수층 부유입자들의 영향이 매우 큼을 잘 보여준다. 일반적으로 수층 부유입자는 저면 퇴적물이 부유된 것으로 간주될 수 있으며, 또한 저면 퇴적물은 각 해역별로 site-specific 하다고 할 수 있다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제18권5호
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• pp.39-45
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• 2013

Many researchers have studied the effectiveness of ultrasound in chemical and environmental engineering fields including material synthesis, pollutant removal, cleaning, extraction, and disinfection. Acoustic cavitation induced by ultrasound irradiation in aqueous phase can cause various sonophysical and sonochemical reactions without any chemicals. However most of the previous studies focused only on the relationships between ultrasonic conditions and the results of sonochemical reactions in lab-scale sonoreactors. As a results of this, only a few studies have been devoted to design and optimization of industrial scale sonoreactors. In this study, the effect of the distance between two opposite transducer modules on sonochemical reactions was investigated in single and dual irradiation systems (334 kHz) for four distances including 50, 100, 150, and 200 mm using KI dosimetry. It was found that the dual irradiation systems provided higher performance in terms of the zeroth reaction coefficient and the cavitation yield compared to the single irradiation systems. The sonochemiluminescence (SCL) images for the visualization of the cavitation field showed that cavitation active zone was larger and sonochemical reaction intensity was much higher in the dual irradiation system than in the single irradiation system.

• 로봇학회논문지
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• 제16권2호
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• pp.94-102
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• 2021

This study addresses a method for 3D reconstruction using acoustic data with heterogeneous sonar devices: Forward-Looking Multibeam Sonar (FLMS) and Profiling Sonar (PS). The challenges in sonar image processing are perceptual ambiguity, the loss of elevation information, and low signal to noise ratio, which are caused by the ranging and intensity-based image generation mechanism of sonars. The conventional approaches utilize additional constraints such as Lambertian reflection and redundant data at various positions, but they are vulnerable to environmental conditions. Our approach is to use two sonars that have a complementary data type. Typically, the sonars provide reliable information in the horizontal but, the loss of elevation information degrades the quality of data in the vertical. To overcome the characteristic of sonar devices, we adopt the crossed installation in such a way that the PS is laid down on its side and mounted on the top of FLMS. From the installation, FLMS scans horizontal information and PS obtains a vertical profile of the front area of AUV. For the fusion of the two sonar data, we propose the probabilistic approach. A likelihood map using geometric constraints between two sonar devices is built and a monte-carlo experiment using a derived model is conducted to extract 3D points. To verify the proposed method, we conducted a simulation and field test. As a result, a consistent seabed map was obtained. This method can be utilized for 3D seabed mapping with an AUV.