• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1915-1920
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• 2004

An edge tone is the discrete tone or narrow-band sound produced by an oscillating free shear layer impinging on a rigid surface. In this paper we present a two-dimensional edge tone to predict the frequency characteristics of the discrete oscillations of a jet-edge feedback cycle by the finite difference lattice Boltzmann method. We use a new lattice BGK compressible fluid model that has an additional term and allow larger time increment comparing a conventional FDLB model, and also use a boundary fitted coordinates. The jet is chosen long enough in order to guarantee the parabolic velocity profile of the jet at the outlet, and the edge consists of a wedge with an angle of ${\alpha}=23^{\circ}$ . At a stand-off distance ${\omega}$ , the edge is inserted along the centreline of the jet, and a sinuous instability wave with real frequency f is assumed to be created in the vicinity of the nozzle and to propagate towards the downstream. We have succeeded in capturing very small pressure fluctuations result from periodically oscillation of jet around the edge. That pressure fluctuations propagate with the sound speed. Its interaction with the wedge produces an irrotational feedback field which, near the nozzle exit, is a periodic transverse flow producing the singularities at the nozzle lips.

• 한국소음진동공학회논문집
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• 제13권6호
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• pp.460-466
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• 2003

The aeroacoustic characteristics and noise reduction method of a centrifugal fan for a bagless vacuum cleaner were studied. The major noise source of vacuum cleaner is the centrifugal fan. The impeller of the fan rotates over 30000 rpm and generates very high-level piercing noise. It was found that the dominant noise source of the fan is generated from the aerodynamic interaction between the highly rotating impeller and stationary diffuser. In order to reduce the high tonal sound generated from the aerodynamic interaction between the impeller and diffuser, tapered impeller was carefully designed and tested. The trailing edge of the tapered impeller was inclined and this reduces the flow interactions between the rotating impeller and the stationary diffuser because of some phase shift. The static efficiency of the new impeller is slightly lower than the conventional one. The overall SPL is reduced about 3.6 dBA. The SPL of blade passing frequency(BPF) is reduced about 6 dBA and the $2^{nd}$ BPF is reduced about 20 dBA. The vacuum cleaner with the tapered impeller has lower noise level than that of the previous impeller and the strong tonal sound was dramatically reduced.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1820-1825
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• 2004

In this paper, we propose a humanoid active audition system which detects the direction of sound and performs speech recognition using just three microphones. Compared with previous researches, this system comprises simpler algorithm and better amplifier system having advantages to increase a detectible distance of sound signal in spite of simple circuit. In order to verify our system's performance, we install the proposed active audition system to the home service robot, called Hombot II, which has been developed at the KIST (Korea Institute of Science and Technology), thus we confirm excellent performance by experimental results

• 대한음성학회지:말소리
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• 제57호
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• pp.85-97
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• 2006

This paper suggests an algorithm that can estimate the direction of the sound source in real time. The algorithm uses the time difference and sound intensity information among the recorded sound source by four microphones. Also, to deal with noise of robot itself, the Kalman filter is implemented. The proposed method can take shorter execution time than that of an existing algorithm to fit the real-time service robot. Also, using the Kalman filter, signal ratio relative to background noise, SNR, is approximately improved to 8 dB. And the estimation result of azimuth shows relatively small error within the range of ${\pm}7$ degree.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.22-25
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• 2006

Direct simulations of aerodynamic sound, especially sound emitted by rapidly rotating elliptic cylinder by the finite difference lattice Boltzmann method (FDLBM). Effect of pile-fabrics for noise reduction is also studied by the finite volume LBM (FVLBM) using an unstructured grid. Second order time integration and third order upwind scheme are shown to be enough for these simulations. Sound sources are detected to be doublets for both cases. For the elliptic cylinder, the doublet is generated in the interaction between the vortex and the edge. For the circular cylinders, they are generated synchronizing with the Karman vortex street, and it is also shown that the pile-fabrics covering the surface of the cylinder reduces the strength of the source.

• 한국공작기계학회논문집
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• 제17권3호
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• pp.122-127
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• 2008

The source of wayside noise for the train are the aerodynamic noise, wheel/rail noise, and power unit noise. The major source of railway noise is the wheel/rail noise caused by the interaction between the wheels and rails. The Structure borne noise is mainly a low frequency problem. The train noise and vibration nearby the elevated railway make one specific issue. The microphone array method is used to search sound radiation characteristics of elevated structure to predict the noise propagation from an elevated railway. In this paper, the train noise and structure borne noise by train are measured. From the results, we investigated the effect on the sound absorption tunnel for elevated railway.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.425-430
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• 2014

The purpose of this study is to establish a clear-cut concept and meaning of soundscape design through an inquiry into the various literatures on the ideologies, features and domains of soundscape design. Soundscape enables us to design various relationship through a sound in that it is important for interaction, namely the relations with sound, environment and people in a region. Soundscape design is an endogenous design which is participated in a large number of people of the region, and it contains various activities such as research study, environmental preservation, creation of sound environment and sound education.

• 한국항해학회지
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• 제22권3호
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• pp.17-25
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• 1998

This paper describes elemental technologies for the creation of three-dimensional(3-D) sound-field to implement the next-generation Ship Handling Simulator with human -computer interaction, known as Virtual Reality. In the virtual reality system, Head-Related Transfer Functions(HRTF's) are used to generate 3-D sound environmental context. Where, the HRTF's are impulse response characterizing the acoustical transformation in a space. This work is divided into two parts, the part Ⅰis mainly for the model constructions of the HRTF's, the part Ⅱis for the control of 3-D sound-field by using the HRTF's . In this paper, as first part, we search for the theory to formulate models of the HRTF's which reduce the dimensionalityof the formulation without loss of any directional information . Using model HRTF's we report results from psychophysical tests used to asses the validity of the proposed modleing method.

• 로봇학회논문지
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• 제3권3호
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• pp.165-175
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• 2008

For an advanced intelligent service, the need of HRI technology has recently been increasing and the technology has been also improved. However, HRI components have been evaluated under stable and controlled laboratory environments and there are no evaluation results of performance in real environments. Therefore, robot service providers and users have not been getting sufficient information on the level of current HRI technology. In this paper, we provide the evaluation results of the performance of the HRI components on the robot platforms providing actual services in pilot service sites. For the evaluation, we select face detection component, speaker gender classification component and sound localization component as representative HRI components closing to the commercialization. The goal of this paper is to provide valuable information and reference performance on appling the HRI components to real robot environments.

• Journal of Information Display
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• 제4권3호
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• pp.29-34
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• 2003

At the paper the method of 3D holographic moving image reconstruction is discused. The main idea of this method is based on the substitution of optically created static hologram by equal diffraction array created by acoustical (AO) field which formed by bulk sound waves. Such sound field can be considered as dynamic optical hologram, which is electrically controlled. At the certain moment of time when the whole hologram already formed, the reference optical beam illuminates it, and due to acoustooptical interaction the original optical image is reconstructed. As the acoustically created dynamic optical hologram is electronically controlled, it can be used for moving 3-dimentional scene reconstruction in real time. The architecture of holographic display for moving scene reconstruction is presented at this paper. The calculated variant of such display laboratory model is given and discussed. The mathematical simulation of step by step images recording and reconstruction is given. The pictures of calculated reconstructed images are presented. The prospects, application areas, shortcomings and main problems are discussed.