• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.249-252
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• 2000

본 논문에서는 수중음향측정을 위한 수직선배열측정 체계 설계 개념을 연구한다. 본 연구에서는 수직선배열 측정체계를 이용한 음향측정 시 고려해야 할 설계 기법들을 고찰하고, 측정 주파수 대역에서 지향지수가 균일하게 유지되는 비선형 센서배열 설계 알고리즘과 피측정 음원의 위치추정을 위한 음향학적 능/수동 추적 알고리즘을 제안한다 제안 알고리즘의 유용성은 시뮬레이션과 해상시험으로 확인한다.

• The Journal of the Acoustical Society of Korea
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• v.18 no.4
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• pp.3-10
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• 1999

Investigations of temperature differences between both cnds of thermoacoustic exchanger generated by acoustic heat transport have been carried out as a function of the position of TAC(Thermo-Acoustic Couple)[1] in a 68-cm-long duct. Fixed with the electric power at 50W, measurements were compared with the theory changing the frequency from 150Hz to 300Hz with 10Hz step. The frequency-position dependent distribution of temperature difference corresponding to the Q-values was obtained with the numerical simulation. Through this distribution, the optimum position of the thermoacoustic exchanger and the optimum driving frequency can be determined.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.6 no.1
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• pp.29-36
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• 2013

The inter-symbol interference(ISI) is one of the main obstacles to reliable high-rate data communication in the shallow underwater acoustic channel. This paper studies on the simulation of adaptive equalizer used as a means of mitigating the ISI in the shallow underwater acoustic communication system. The underwater channel is modeled as a superposition of multiple paths, whose lengths and relative delays are calculated from the channel geometry. Based on this channel model, computer simulations are carried out to investigate the performance of adaptive equalizer in the shallow underwater acoustic channel.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.696-700
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• 2007

In case of dome-typed gymnastics training floor, since its form takes shape of the focus of sound, in the occasion when the finishing-material was used with the sandwich panel that prominent in reflexibility, and because the reverberation of sound in indoor is too loud, a smooth practice and teaching is very difficult. As this indoor gymnastics training floor, standing at its character, is required simultaneously the idea communication between the player and the coach, and the acoustic capability regarding to the clearness of music, besides the sport activity, the method to minimize the acoustic defect should be urgently contrived from the stages of design and beginning of construction. On this viewpoint, after investigation on the confidence of the surveyed value and the estimated value using acoustic simulation, and use of the changed finish-material, this thesis intends to design the dome-typed gymnastics training floor that secured the optimized acoustic condition. It is also considered that such result of the study could be utilized as the useful data that enables to improve the retrenchment effect of the construction cost as well as the acoustic performance, by means of the prediction control on the acoustic problem from the stage of design, for the occasion when the similar indoor sport gymnasium is planning to build for the near future.

• Journal of the Korea Society for Simulation
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• v.16 no.4
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• pp.1-12
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• 2007

This paper describes and explains that the engagement level model of submarine can be used in underwater engagement simulation taking reuse, interoperability, and extension to the engineering leveled simulation into consideration. WBS(Work Break-down Structure), internal data interface, and I/O data about the engagement level model of submarine are developed. It describes the modeling method of components of submarine model as well. In this paper, the non-acoustic detection and stealth models are excluded because those models are not related to the underwater engagement, so the excluded models need to be developed in the future.

• The Journal of the Acoustical Society of Korea
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• v.24 no.8
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• pp.469-480
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• 2005

There have been always some difficulties in target setting and conditioning of acoustic performances or the Korean traditional music hall due mainly to the lack of the information on the sound radiation characteristics of Korean musical sources. As the 2nd experiment succeeding the previous study[1], the radiation characteristics of eight typical Korean traditional musical sources were investigated if precision. The selected musical sources were Geomungo, Haegeum (string), Piri, Taepyeongso (woodwind), Buk, Kwaengguari, Jing (drum), and male Pansori Chang (vocal Performance). The results show that the directivity pattern of each instrument is different and has their own directivity characteristics. Measured directional and spectral characteristics of traditional Korean music sources were implemented into the computation of architectural acoustic measures. Significant differences in the acoustic measures at receiver positions were observed between the results in using the omni-directional source and the directional one. In order to investigate the acoustical characteristics of the instruments depending on the spatial variation four different shapes of halls were introduced including rectangular, fan. horse-shoe and geometrical shapes. Room acoustical parameters such as RT, SPL, C80, LF, STI were calculated at each type or hall. As the results, It was found that the rectangular hall has the most high clarity. lateral energy and STI values among low shapes of halls. It is thought that the suggested source data and design method can be used as a basic reference in the future acoustic design of performance halls for the Korean traditional music.

• The Journal of the Acoustical Society of Korea
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• v.39 no.5
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• pp.400-405
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• 2020

To analyze the flow distribution formed by multiple acoustic sources, the distribution of acoustic streaming speed caused by an ultrasonic transducer composed of two identical piezoelectric vibrators was examined for various angles between the sound sources. In order to measure the distribution of the speed along the acoustic axis of the transducer, a simple measurement method using a droplet indicator having density similar to that of water is suggested. The simulation results calculated by a numerical method and experimental results showed a similar tendency, and the change of flow speed distribution with the intersection angle between acoustic beams radiated from two acoustic sources was analyzed.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.3
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• pp.419-426
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• 2017

This paper describes an acoustic echo canceller with double-talk using BSS(: Blind Signal Separation) based on the geometric concept. The acoustic echo canceller may be deteriorated or diverged during the double-talk period. So we use the blind signal separation to detect the double talking by separating the near-end speech signal from the mixed microphone signal. In the closed reverberation environment, the blind signal separation extracts the near-end signal from unknown signals with the transformation and rotation based on the geometric concept. By this method, the acoustic echo canceller operates irrespective of double-talking. We verified performances of the proposed acoustic echo canceller by computer simulations. The results show that the acoustic echo canceller with this algorithm detects the double-talk periods thoroughly, and operates stably in the normal state without diverging of coefficients after ending the double-talking.

• Journal of Korean Association for Spatial Structures
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• v.11 no.1
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• pp.67-75
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• 2011

The present work investigate the effect of sound reinforcement systems on the acoustics of a large dome stadium using a computer simulation. The acoustics of a dome stadium was predicted analyzed by varying room absorption, as well as the configuration of speakers including their directivity, installed height, and numbers. It was found that both D50 and RASTI were improved by increasing room absorption. Larger EDTs were observed according to the increase of room absorption at mid and high frequencies. On the other hand, RT did not show any significant correlation with the changes in room absorption, which might be the effect of a forced linear fitting for non -linear energy decay process. With respect to the speaker configuration, the speech intelligibility of a sound reforcement system installed at higher placed more relied upon their directivity rather than room absorption, Also, lower placing of speakers was found to be effective in decreasing RTs regardless of room absorption.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.2
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• pp.237-245
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• 2012

This paper describes an acoustic echo canceller with double-talk by the blind signal separation. The acoustic echo canceller is deteriorated or diverged in the double-talk period. So we use the blind signal separation to estimate the near-end speech signal and to eliminate the estimated signal from the residual signal. The blind signal separation extracts the near-end signal with dual microphones by the iterative computations using the 2nd order statistical character. Because the mixture model of blind signal separation is multi-channel in the closed reverberation environment, we used the copied coefficients of echo canceller without computing the separation coefficients. By this method, the acoustic echo canceller operates irrespective of double-talking. We verified performances of the proposed acoustic echo canceller by simulations. The results show that the acoustic echo canceller with this algorithm detects the double-talk periods thoroughly, and then operates stably in the normal state without the divergence of coefficients after ending the double-talking. And it shows the ERLE of averagely 20dB higher than the normal LMS algorithm.