• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.505-508
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• 2002

• The Journal of the Acoustical Society of Korea
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• v.3 no.2
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• pp.30-34
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• 1984

본 논문에서는 인코히어런트광 매트릭스-벡터곱셈기를 이용하여 입력 데이터를 광학적으로 DFT 할 수 있는 방법을 연구하였다. DFT의 웨이팅함수를 매트릭스로 나타내어 본 논문에서 제시한 2 개의 성분 분할 방법을 이용하여 마스크상에 부호화하고 광매트릭스-벡터곱셈기내에 고정시켜서 입력 데이터와 광학적으로 곱하도록 하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.131-134
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• 1999

This paper considers the acoustical characteristics of the mechanical valve employed in the Korean type Artificial Heart. $Bj\"{o}rk-Shiley$ tilting disc valve was chosen for the study and acoustic measurements were performed for the artificial heart operated in a mock circulation system as well as implanted to an animal as a Bi Ventricular Assist Device (BVAD). In the mock system, three different conditions of the valve were examined which were normal, damaged (torn off), pseudothrombus attached. Microphone measurements for the BVAD were carried out at a regular time interval for 5 days after the implantation operation. Of the recorded acoustic emissions from the artificial heart, click sounds mainly originated from the valves were further analyzed using Multiple Signal Classification (MUSIC) for estimating their spectral properties. It was shown that the spectral peaks below 4 kHz and the optimal order number for MUSIC, equivalent to the number of the spectral component, might be the key parameters which were highly correlated to the physiological states of the valve like the mechanical damage of the valve or the formation of thrombus on the valves.

• The Journal of the Acoustical Society of Korea
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• v.14 no.4
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• pp.100-108
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• 1995

This study is aimed to show that revised prediction method in road traffic noise after comparing prediction method of National Institute of Environmental Research with that of the Acoustical Society of Japan. For this purpose, prediction equation and caluation procedure of each case was programmized and data predicted by each method were compared with those measured in the 14 fields. The result show that data predicted by 14 fields. The result show that data predicted by the method proposed in this study were closer to the data measured in the fields than those predicted by National Institute of Environmental Research and the Acoustical Society of Japan in the surroundings of urban express way (include highway) and general traffic road where the vehicle speed is higher than 40km/h.

• Phonetics and Speech Sciences
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• v.2 no.2
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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.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.9
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• pp.71-77
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• 2008

Microcellular foaming plastics create a sensation at polymer industrial for lowering product costs and overcoming a lowering of mechanical intensity. Among many advantages, microcellular foaming plastics is well known to have a good acoustical properties. This research based on the experiment of sound absorption and transmission characteristics inquire into acoustical properties of microcellular foaming plastics. Difference of transmission loss of microcellular foaming plastics and solid materials was defined as cell effect. Also, cell effect is expressed by sound reflection and sound absorption. This study is expected to fundamental research to present economical, functional alternative plan for products using sound absorption and transmission materials.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.230-233
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• 2001

Revision of KS, Korean Standards, is currently actively discussed. It is just the time for a new world class standards under the new system with WTO, World Trade Organization. This paper is a part of "Researches on the Standards in the Building Acoustic Field", as one of KS revision projects. The aim of this study is to define the requirements for measuring the reverberation time of rooms with reference to other acoustical parameters. In the former KS, there is no items matched with this purpose. Therefore measuring reverberation time and other room acoustical parameters with confidential test procedure was impossible. On these basis, a new part of KS is proposed, and some problems remained and further discussions in the proposed draft are described in this study.

• Journal of KSNVE
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• v.9 no.1
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• pp.77-84
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• 1999

The sharp and highly fluctuating characteristics of the building services noises cause much psychological discomfort to dwellers. To evaluate the noises effectively. it is necessary to develope an evaluation procedure which can well reflect the psychological influences of the noises. In this study, to develope the effective evaluation procedure for the building services noise. Korean vocabularies which can express the feelings for them was investigated. And then, through a series of psycho-acoustical experiments for various housing equipment noises. we analyzed psychological factors that influence to subjective feelings of persons.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.144-150
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• 2008

In this study, the PVDF (polyvinylidene fluoride) piero-film sensor was applied to measure the internal quality of apple. The developed sensor detected the response signal through apple after mechanical impact on the surface of apple. The acoustical parameters at time domain such as rise time (RT), ring down count (RC), energy (EN), event duration (ED) and peak amplitude (PA) and acoustical parameter at frequency domain such as spectral density (SE) were analyzed. The size of waveform decreased as storage time of apple increased. The frequency at maximum magnitude was shifted to lower frequency band according to the storage time. The acoustical parameters showed strong relationship with storage time. The multiple linear regression equation was developed to estimate storage time of apple using the acoustical parameters at time domain and its coefficient of determination was 0.97. The internal quality of apple according to storage time is predictable using developed PVDF sensor and acoustical parameters defined in this study.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.387-390
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• 1999

This study Is on the experimental explanation of Intonation of news sentences with focus on the Korean noun phrase, pronounced by announcers. For this, with a basic form as $'{\_}case particle\;+\;{\_}adnominal ending\;+\;Noun'$ which is a common structure in these sentences, we classified NPs according to the added constituents and examined their intonation. And with examining the connection or the breaking of intonation patterns, we described the relation between neighbouring words which build 'a rhythmic unit'.