• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.71-77
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• 2000

An axisymmetric supersonic jet is simulated at a Mach number of 1.5 and a Reynolds number of $10^5$ to identify the mechanism of sound radiation from the jet. The present simulation is performed based on the high-order accuracy and high-resolution ENO(Essentially Non-Oscillatory) schemes to capture the time-dependent flow structure representing the sound source. In this simulation, optimum expansion jet is selected as a target, where the pressure at nozzle exit is equal to that of the ambient pressure, to see pure shear layer growth without effect of change in jet cross section due to expansion or shock wave generated at nozzle exit. Shock waves are generated near vortex rings, and discernible pressure waves called Mach wave are radiated in the downstream direction with an angle from the jet axis, which is characteristic of high speed jet noise. Furthermore, vortex roll-up phenomena are observed through the visualization of vorticity contours.

• Journal of KSNVE
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• v.5 no.1
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• pp.37-48
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• 1995

The prediction of sound pressure using acoustic holography has been recognized as a useful tool for the visualization of sound field. Cylindrical acoustic holography amongst acoustic holographic methods planar, spherical, and cylindrical ones-has a wide range of application since its rather simple construction and easy implementation for the sources. To utilize the propery of cylindrical holographic method, estimation errors associated with holographic parameters such as aperture size and sampling space must be envisaged. In this these errors have been studied by numerical simulation and the relation between the errors and the spectrum in wavenumber domain is described. The results are also confirmed by simple experiments.

• 중국학논총
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• no.66
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• pp.85-103
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• 2020

We use prototypes (also known as referent in semiotics) when we understand the outside world. Different language users use different prototypes to decode the same sound. When we learn Chinese language as a foreign language, during it's sound perceptual process, Korean learners' target language prototypes are different from Chinese native speakers'. The purpose of the paper is to examine the theory of speech perception and the theory of constructivism teaching, and to suggest to the Chinese language teachers to have Cunstructivist approach while they design there teaching course. For this, we concerned three things: First is to review speech perception theory and constructivism teaching theory. Second based on the preceding study, we review that learner's prototypes are different from Chinese native speaker and this cause the error of listening and pronunciation. Finally, we introduced two simple speech visualization programs developed to help us learn pronunciation.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.11
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• pp.20-28
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• 2009

• Journal of the Korean Society for Precision Engineering
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• v.26 no.11
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• pp.7-11
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• 2009

• The KSFM Journal of Fluid Machinery
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• v.7 no.1 s.22
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• pp.17-23
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• 2004

Aeroacoustic characteristics of sirocco fan used in Over-The-Range (OTR) has been analyzed in this paper. A microwave hood combination over the gas range is short for the OTR. The flow phenomena of the double-sided sirocco fan was analyzed numerically and experimentally by using commercial code and three dimensional PIV for flow visualization. Also, microphone array is used in order to understand acoustic characteristics of OTR. Two dimensional unsteady flow and acoustic simulation is tried to qualitatively estimate the effects of tonal noise and broadband noise on the overall sound pressure level. It is found that tonal sound is generated from the strong interaction between the impeller and cutoff while broadband sound is generated from the strong secondary flows along the scroll surface. To reduce the noise level, the V-shape cut-off was applied to improve the sound quality by reducing tonal noise. So the peak noise at BPF (Blade Passing Frequency) was almost reduced. The shape of flow-guide to suppress the secondary flow over the scroll surface was carefully checked. It is found that this affects flow pattern at the fan exit and reduces the broad band noise. Through this numerical and experimental study, the sound pressure level was lowered by 4dBA compared to that of the previous fan at the operating point.

• Trans-
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• v.1
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• pp.91-116
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• 2016

The theme of this research is the music visualization on stage. As the collaborated work, combining the dance, images with the Isang Yun's music, is showing the staged music, which is expressing the music not only through the sound but also the visualization. In the process of visualizing the music through the body and images on the stage, Isang Yun's musics are recreated in the hand of today's artists. The study found that the recreated work from the new point of view, like Interview with Isang Yun can be the bridge between the composer and today's artists and we can see the future through it. Even though, this paper analyzed the work through the aspects of dance and images, the main theme of the work is focusing how can we deliver the music in the new representative form through formative visualization on the stage.

• Archives of design research
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• v.18 no.2 s.60
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• pp.211-218
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• 2005

As digital Information equipment is new arrival, new paradigm such as 'function exist but form don't' is needed in the field of design. Therefore, the activity of design is focused on the relationship of human and machine against visual form. For that reason, it is involved emotional factor in the relationship and studied on new field, the emotional interlace. The goal of this paper is to suggest the way of emotional interface on searching multimedia data. The main target of paper is effect sound and human's step and the main way of research is visualization after measuring and analyzing numerically similarity level among emotion-words. This paper suggests the theoretical bad(ground such as personal opinion, the character of auditory information and human's step and case studies on the emotion research. The experimental content about sound is fueled from my previous research and the main experimental content about human's step is made with regression-expression to substitute Quantification method 1 for value about stimulation. The realistic prototype to apply the research result will is suggested on the next research after studying the search environment.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.7
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• pp.586-603
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• 2004

One of the subtle problems that make noise control difficult for engineers is “the invisibility of noise or sound.” The visual image of noise often helps to determine an appropriate means for noise control. There have been many attempts to fulfill this rather challenging objective. Theoretical or numerical means to visualize the sound field have been attempted and as a result, a great deal of progress has been accomplished, for example in the field of visualization of turbulent noise. However, most of the numerical methods are not quite ready to be applied practically to noise control issues. In the meantime, fast progress has made it possible instrumentally by using multiple microphones and fast signal processing systems, although these systems are not perfect but are useful. The state of the art system is recently available but still has many problematic issues : for example, how we can implement the visualized noise field. The constructed noise or sound picture always consists of bias and random errors, and consequently it is often difficult to determine the origin of the noise and the spatial shape of noise, as highlighted in the title. The first part of this paper introduces a brief history, which is associated with “sound visualization,” from Leonardo da Vinci's famous drawing on vortex street (Fig. 1) to modern acoustic holography and what has been accomplished by a line or surface array. The second part introduces the difficulties and the recent studies. These include de-Dopplerization and do-reverberation methods. The former is essential for visualizing a moving noise source, such as cars or trains. The latter relates to what produces noise in a room or closed space. Another mar issue associated this sound/noise visualization is whether or not Ivecan distinguish mutual dependence of noise in space : for example, we are asked to answer the question, “Can we see two birds singing or one bird with two beaks?"

• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.2
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• pp.83-89
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• 1994

It is important for an ultrasonic testing to know the sound pressure field and the directivity of ultrasonic waves propagating in a solid. The directivity of ultrasonic wave is closely related to the sensitivity, the scanning pitch, the arrangement of angle probe, and the defect kind in ultrasonic testing. This paper describes on the directivity measurement of ultrasonic wave using ultrasonic wave visualization method. The directivity of the shear wave emitted from the angle probes were constant during propagation. The difference of directivity was existed between 2MHz and 4MHz angle probes. The centers of directivity were located backward from the incident poing and inside of the angle probe and were not changed during the wave propagation.