• Proceedings of the Korean Society of Computer Information Conference
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• 2021.01a
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• pp.269-271
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• 2021

본 논문에서는 실제 현실에서 표현되는 소리의 특징인 파동(Sound wave)과 흐름(Sound flow) 그리고 회절(Diffraction of sound)을 가상환경에서 실시간으로 표현할 수 있는 방법을 제안한다. 우리의 접근 방식은 소리가 재생되는 위치로부터 장애물 여부를 판단하고, 장애물이 존재할 시, 장애물로 인해 반사와 회절된 새로운 소리 위치를 계산한다. 이 과정에서 레이트레이싱 기반으로 장애물과의 충돌 여부를 판단하고, 충돌에 의해 굴절된 벡터를 이용하여 장애물 너머에서 들리는 소리의 크기를 계산하며, 충돌된 레이의 개수에 따라 소리의 크기를 감쇠시킨다. 본 논문에서 제안하는 방법을 이용한 소리의 회절은 물리 기반 접근법에서 나타나는 회절 형태를 실시간으로 표현했으며, 장애물에 따라서 회절 패턴이 변경되고, 이에 따라 소리의 크기가 자연스럽게 조절되는 결과를 보여준다. 이 같은 실험은 실제 현실에서 나타나는 소리의 퍼짐과 같은 특징을 거의 유사하게 복원해냈다.

• Proceedings of the KSME Conference
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• 2004.11a
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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.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.67-71
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• 2003

The propagation characteristics of the impulse wave discharged from the exit of a perforated pipe is investigated through a simple shock tube facility. The pressure histories and directivities of the impulse wave propagating outside from the exit of pipe with several different configurations are analyzed for the range of the incident weak shock wave Mach number between 1.02 and 1.2. In the shock tube experiments, the impulse wave are visualized by a Schlieren optical system for the purpose of understanding its propagation characteristics. The experimental results show that for the near sound field the impulse noise strongly propagates toward to the pipe axis, but for the far sound field the impulse noise uniformly propagates toward to the omnidirections, indicating that the directivity pattern is almost same regardless of the pipe type. Especially, it is shown that the perforated pipe has a little performance to reduce the impulse noise only for the near sound field

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.4
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• pp.307-314
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• 2011

This study was focused on the influence of soundscape provided to the interior landscape on the improvement of occupants' sound environment. When soundscape was provided to occupants together with the interior landscape rather than simply providing interior landscape, the occupants' satisfaction seemed to be improved. The most preferred sound source among the three sound sources was considered as the sound of the grasshopper. When both of the interior landscape and the landscape substances was provided, the adjectives with the average difference of more than 1 are "Vicissitudinous", "Elegant" and "Cheerful". When the interior landscape and the sound source were provided, such adjectives as "Vicissitudinous", "Complex" and "Cheerful" are extracted. When all the variables were provided, such adjectives as "Vicissitudinous", "Abundant" and "Cheerful" seem to show the difference of more than 1. Regarding "Vicissitudinous", it was possible to know that the average difference of more than 1.5 was the biggest. Regarding the relative values of the ${\alpha}$ wave and the ${\beta}$ wave for each part, it seemed that the highest ${\alpha}$ wave was generated on the left parietal lobe of P3, while the lowest ${\beta}$ wave was generated on the left and right frontal lobes of Fp1 and Fp2. According to this study, it was shown that the soundscape and the interior landscape seemed to influence the improvement of the occupants' sound environment.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.117-119
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• 2004

In order to successfully exploit underwater resources, the first step would be a marine environmental research and exploration on the seafloor. Traditionally one sets up a long-term underwater experimental unit on the seafloor and retrieves the unit later after a certain period time. Essential to these applications is the reliable teleoperation and telemetering of the unit. This study presents ultrasonic-wave remote control system and an underwater sound recognition algorithm that can identify the sound signal without the influence of disturbances due to underwater environmental changes. The proposed method provides a means suitable for units which require low power dissipation and long-time underwater operation. We demonstrate its ability of securing stability and fast sound recognition through experimental methods.

• International Journal of Aeronautical and Space Sciences
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• v.5 no.2
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• pp.18-27
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• 2004

An axisymmetric supersonic jet is simulated at a Mach number 2.1 and a Reynolds numberof 70000 to identify the mechanism of Mach wave generation and radiation from the jet. In orderto provide the near-field radiated sound directly and resolve the large-scale vortices highly.high-resolution essentially non-oscillatory(ENO) scheme, which is one of the ComputationalAeroAcoustics(CAA) techniques, is newly employed. Perfectly expanded supersonic jet is selectedas a target to see pure shear layer growth and Mach wave radiation without effect of change injet cross section due to expansion or shock wave generated at nozzle exit. The sound field ishighly directional and dominated by Mach waves generated near the end of potential core. Thenear field sound pressure levels as well as the aerodynamic properties of the jet, such asmean-flow parameters are in fare agreement with experimental data.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2066-2070
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• 2003

This experimental study describes the propagation characteristics and suppression of the impulse noise emitted from the exit of a perforated pipe attached to the open end of a simple shock tube. The experiment is performed through the systematic change of the shock wave Mach number and the geometrical parameters such as the porosity, hole diameter and length of the perforated pipe. The experimental results for the near and far sound field are presented and explained in comparison with those for a straight pipe. The results obtained show that for the near sound field the impulse noise strongly propagates toward to the pipe axis, but for the far sound field the impulse noise uniformly propagates toward to the all directions, indicating that the directivity pattern is almost same regardless of the pipe type. Moreover, the noise reduction performance of perforated pipe depends upon the condition of sound field. For the near sound field the perforated pipe has a little performance to suppress the impulse noise, but for the far sound field the perforated pipe has little performance to suppress the impulse noise.

• Proceedings of the IEEK Conference
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• 2000.06e
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• pp.99-102
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• 2000

This study analyze of reflection wave to Acoustic stimulation on acupoints and contrast parts for objectification of the meridian substance. In order to verify meridian pathway and channel theory of bio-energy in body. It was analyzed response characteristic of reflection waves after acoustic stimulation by sound wave of 5 specific tones. The response characteristics of reflection are measured by the average current magnitude of meridian. The current variation ratio are Live Meridian(gung) 33.2%, Heart Meridian(sang) 30.7%, Kidney Meridian (gak) 33.1%, Spleen Meridian(chi) 33.9%, Lung Meridian (wo) 30.7% compare with contrast parts (non-acupoint and meridian). Therefore meridian is distinguished to non-meridian and 5 vital meridians have relationship with sound wave of 5 specific tones.

• The Journal of the Acoustical Society of Korea
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• v.21 no.2
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• pp.110-119
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• 2002

Acoustic characteristics of water sediment were experimentally studied in laboratory. Water saturated sand sediment less than the grain size of 0.5 mm diameter is uniformly distributed in an acryl box (100 mm×100mm×42mm) with material thickness 1 mm. Pores in the acryl box are modeled as the structure of cylindrical pore tubes (diameter 3 mm and length 42 mm) filled with water. Cylindrical pore tubes have porosities 0%, 5%, 11%, 18% and 26 % controlled by the tube numbers. Transmitted acoustic waves through sand sediment specimen are analyzed as the functions of porosity and frequency from 0.3 MHz to 4 MHz. Transmitted acoustic waves are mixed with the first-kind wave from whole specimen and the second-kind wane from cylindrical pore tubes. For the center frequency 1 MHz, the first kind wave is dominant but for the center frequency 2.25 MHz, the second kind wave is dominant. In the case of the first-kind wave, as the porosity increases, the transmission coefficient decreases and the sound speed decreases to the sound speed of water. As the frequency increases, the transmission coefficient decreases but the sound speed is almost constant. In the case of the second-kind wave, as the porosity increases, the transmission coefficient increases but the sound speed is almost constant. The transmission coefficient and the sound speed are almost constant as a function of frequency.

• Research in Plant Disease
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• v.20 no.1
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• pp.1-7
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• 2014

Plant growth is considered the sum of cell proliferation and subsequent elongation of the cells. The continuous proliferation and elongation of plant cells are vital to the production of new organs, which have a significant impact on overall plant growth. Accordingly, the relationship between environmental stimuli, such as temperature, light, wind, and sound waves to plant growth is of great interest in studies of plant development. Sound waves can have negative or positive effects on plant growth. In this review paper we have summarized the relationship between sound waves and plant growth response. Sound waves with specific frequencies and intensities can have positive effects on various plant biological indices including seed germination, root elongation, plant height, callus growth, cell cycling, signaling transduction systems, enzymatic and hormonal activities, and gene expression.