• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.08a
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• pp.177-185
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• 2004

This paper describes Listening Decision Aid Simulator (LDAS) to provide a decision-supporting tool that can reproduce real-like listening situations focused on the duty officer's two ears. The sound propagation mechanism from a whistle to listener's two ears is established at first, and the spatial transfer coefficients of a bridge door are measured at training vessel. Then, the construction works with the spatial transfer coefficients and its evaluation experiments with five collision accidents are carried out. As results from tests, the five cases can be judge by LDAS; it led to the insight of practical use of LDAS as one of the decision supporting system in collision accidents.

• Journal of the Korean Institute of Navigation
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• v.22 no.3
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• pp.27-34
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• 1998

The paper is the second part on the 3-D sound-field creation implementing the Virtual Reality Ship Handling Simyulator(VRSHS). As mentioned in the previous part Ⅰ, the spatial impression, which arose from reproduced 3-D sound-field , give natural sound environmental context to a listener. This spatial impression is due to the reverberation by reflections and ,is can be obtain by using Head-Related Transfer Function(HRTF). In this work, we foumulate early and late reverberation models of the HRTF's with theoretical control factors based on the sound-energy distribution in an irregularly shaped enclosures. Using the reverberation models, we report results from psychophysical tests used to asses the validity of the proposed 3-D soud-field control method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.620-628
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• 2005

Spatial control of sound is essential to deliver better sound to the listener's position in space. As it can be experienced in many listening environments, the quality of sound can not be manifested over every position in a hall. This motivates us to control sound in a region we select. The primary focus of the developed method has to do with the brightness and contrast of acoustic image in space. In particular, the acoustic brightness control seeks a way to increase loudness of sound over a chosen area, and the contrast control aims to enhance loudness difference between two neighboring regions. This enables us to make two different kinds of zone - the zone of quiet and the zone of loud sound - at the same time. The other perspective of this study is on the direction of sound. It is shown that we can control the direction of perceived sound source by focusing acoustic energy in wavenumber domain. To begin with, the proposed approaches are formulated for pure-tone case. Then the control methods are extended to a more general case, where the excitation signal has broadband spectrum. In order to control the broadband signal in time domain, an inverse filter design problem is defined and solved in frequency domain. Numerical and experimental results obtained in various conditions certainly validate that the acoustic brightness, acoustic contrast, direction of wave front can be manipulated for some finite region in space and time.

• Journal of Environmental Science International
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• v.29 no.11
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• pp.1141-1151
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• 2020

The impact of sound speed variability in the sea is the very important on acoustic propagation for the underwater acoustic systems. Understanding of the temporal and spatial variability of ocean sound speed in the sea around the Ieodo were obtained using oceanographic data (temperature, salinity). from the Korea Oceanographic Data Center, collected by season for 17 years. The vertical distributions of sound speed are mainly related to seasonal variations and various current such as Chinese coastal water, Yellow Sea Cold Water (YSCW), Kuroshio source water. The standard deviations show that great variations of sound speed exist in the upper layer and observation station between 16 and 18. In order to quantitatively explain the reason for sound speed variations, Empirical Orthogonal Function (EOF) analysis was performed on sound speed data at the Line 316 covering 68 cruises between 2002 and 2018. Three main modes of EOFs respectively revealed 55, 29, and 5% the total variance of sound speed. The first mode of the EOFs was associated with influence of surface heating. The second EOFs pattern shows that contributions of YSCW and surface heating. The first and second modes had seasonal and inter-annul variations.

• The Journal of the Acoustical Society of Korea
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• v.31 no.5
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• pp.340-351
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• 2012

In this paper, we proposed the stereo-10.2channel blind upmix algorithm for the enhanced 3D sound. Recently, consumers want to enjoy better sound and the use of a various of multichannel configuration has been steadily improved. Thus, upmix algorithms have been researched. However, conventional upmix algorithms have the problem that distorts the spatial information of original source. To solve this problem and enhance the spatial sound quality, we proposed front and rear channel gain adjustment and 10.2 channel upmix algorithm for each additional channel. The listening test results show that it maintains spatial information of stereo input and enhances 3D sound effects unlike other conventional upmix algorithms.

• The Journal of the Acoustical Society of Korea
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• v.16 no.2
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• pp.16-25
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• 1997

A new method to model the HRTF's(Head-Related Transfer Function), which could give improvement of the sound localization accuracy using the spatial effects by the reflected sound wave transfer characteristics, is proposed. When using the HRTF model having reflected sound wave transfer characteristics, the accuracy of sound localization was quite improved up to about 23%, compared with using the direct wave transfer characteristics only. Furthermore, it is verified that the spatial impression could be a factor to enhance the ability of sound localization.

• Journal of Broadcast Engineering
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• v.28 no.2
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• pp.213-229
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• 2023

In this paper, we introduce a spatial sound rendering system that provides 6DoF spatial sound in real time in response to the movement of a listener located in a virtual environment. This system was implemented using MPEG-I AEP as a development environment for the CfP response of MPEG-I Immersive Audio and consists of an encoder and a renderer including a decoder. The encoder serves to offline encode metadata such as the spatial audio parameters of the virtual space scene included in EIF and the directivity information of the sound source provided in the SOFA file and deliver them to the bitstream. The renderer receives the transmitted bitstream and performs 6DoF spatial sound rendering in real time according to the position of the listener. The main spatial sound processing technologies applied to the rendering system include sound source effect and obstacle effect, and other ones for the system processing include Doppler effect, sound field effect and etc. The results of self-subjective evaluation of the developed system are introduced.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.7
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• pp.701-710
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• 2008

Including a TV set and a monitor, personal audio system is raising a great interest. In this study, we applied a method to make a good bright zone around the user and dark zone to other region by maximizing the ratio of sound energy between the bright and dark zone. It has been well known as acoustic contrast control. We have attempted to use a line loudspeaker array system to localize the sound in our listening zone. It depends on the size of the zone and array parameters, for example, array size, loudspeaker unit spacing, wave length of sound. We have considered these parameters as spatial variables and studied the effects. And we have found that each spatial variable has its own characteristic and shows very different effect. Genetic algorithms are introduced to find out the optimum value of spatial variables. As a result, we can improve the result of the acoustic contrast control by optimum value of spatial variables.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.857-861
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• 2004

An active method that improves low frequency characteristics of a reverberation chamber has been proposed. Spatial uniformity of sound pressure at low frequency has been increased by applying active noise control system. The system acts as frequency selective damping materials, which decreases resonance at low frequency and leave high frequency sound field as it is. Linearity of the chamber, which is essential for sound power measurement in the chamber, is guaranteed since fixed control logic has been adopted. Simple application and tests have been done in a small sized rectangular reverberation chamber which has 400Hz cutoff, Loud speakers were used to simulate a noise source and to construct an active noise control system. The spatial distribution of a sound field at 250Hz, 315Hz and 400Hz bands has been measured before and after control. The standard deviation of sound field has been decreased from 3.4dB to 2.5dB. The results show the possibility of active control system as a sound diffuser.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.12
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• pp.217-223
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• 2013

This paper proposes a spatial audio reproduction system based on audio fingerprinting that combines the audio fingerprinting and the spatial audio processing. In the proposed system, a salient audio peak pair fingerprint based on modulation spectrum improves the accuracy of the audio fingerprinting system in real noisy environments and spatial audio information as metadata gives a listener a sensation of being listening to the sound in the space, where the sound is actually recorded.