• The Journal of the Acoustical Society of Korea
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• v.32 no.2
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• pp.104-115
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• 2013

In a shallow water waveguide, reverberation signals and their Doppler effects form the primary limitation on sonar system performance. Therefore, in the reverberation-limited environment, it is necessary to estimate the reverberation level to be encountered under the conditions in which the sonar system is operated. In this paper, high-frequency reverberation model capable of simulating the reverberation signals received by a high-speed moving source in a range independent waveguide is suggested. In this model, eigenray information from the source to each boundary is calculated using the ray-based approach and the optimizing method for the launch angles. And the source receiving position changed by the moving source is found by a scattering path-finding algorithm, which considers the speed and direction of source and sound speed to find the path of source movement. The scattering effects from sea surface and bottom boundaries are considered by APL-UW scattering models. The model suggested in this paper is verified by a comparison to the measurements made in August 2010. Lastly, this model reflects well statistical properties of the reverberation signals.

• The Journal of the Acoustical Society of Korea
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• v.36 no.5
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• pp.353-360
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• 2017

The single sensor based acoustic reflection control system separates the incident and reflected signals from the single sensor output, and reduces the reflected signal by generating an out-of-phase signal from the incident signal component. In this paper, we propose an optimal filter design method for a single sensor based reflection control system. In the proposed method, it is shown that the optimum control filter design is possible by using the measured impulse responses of the reflection and control paths. The reflection control algorithm based on the proposed optimal filter achieves better performance than the conventional adaptive filter-based algorithm and effectively controls the reflection without the initial convergence time. We performed computer simulations using the signals obtained in a 1-dimensional acoustic duct environment, and from the simulation results, it was confirmed that the proposed optimal filter has robust performance even in noisy environment.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.05a
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• pp.397-400
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• 2020

본 논문은 영화에 나오는 효과음을 자막으로 생성해주는 자동자막생성을 제안하며, 그의 첫 단계로써 다중 사운드 분류 모델을 제안하였다. 고양이, 강아지, 사람의 음성을 분류하기 위해 사운드 데이터의 특정벡터를 추출한 뒤, 4가지의 기계학습에 적용한 결과 최적모델로 딥러닝이 선정되었다. 전처리 과정 중 주성분 분석의 유무에 따라 정확도는 81.3%와 33.3%로 확연한 차이가 있었으며, 이는 복잡한 특징을 가지는 사운드를 분류하는데 있어 주성분 분석과 넓고 깊은 형태의 신경망이 보다 개선된 분류성과를 가져온 것으로 생각된다.

• The Journal of the Acoustical Society of Korea
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• v.21 no.8
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• pp.679-685
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• 2002

Low-frequency mono-static reverberation model for shallow-water environment is presented. It is necessary to develop the transmission loss model to calculate the sub-bottom interaction because the ray-based transmission loss model is difficult to compute the pressure accurately which penetrates the bottom medium. In this paper reverberation level is calculated using the RAM (Range dependent Acoustic Model) to augment the multi-path expansion model because it does not estimate transmission loss accurately in shallow water. The signals generated by the L-HYREV and the GSM are compared with the observed signals and it is showed that the L-HYREV model provides a closer fit to the observed signals than those obtained using the GSM.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.192-197
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• 2017

Typical materials including concrete behaves with positive poisson's ratio when external force is applied. However, it is also available to manufacture a grating system which has negative poisson's ratio(Auxetic). In this study, double arrow type 2-D auxetic mesh was manufactured and mechanical behaviors were observed. Also, direct tensile tests of cementitious composites reinforced by auxetic mesh were performed and the results were compared with composites reinforced by typical mesh. The results showed that auxetic mesh more effectively restrained the deformation(shortening) of cementitious composites perpendicular to the load direction comparing with typical mesh.

• Journal of the Society of Disaster Information
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• v.12 no.3
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• pp.235-241
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• 2016

Recently our country was entering a high-tech society with social and economic development. However, the individual's ability to respond to disasters is lowered by the increase in complexity society. Accurate situation assessment and disaster response by a margin of personal information that can identify when a disaster has been difficult. Until now, by leveraging Standard speaker was the emergency alert broadcast. However, it was difficult to have regular speakers reverberation, a distinct attenuation of sound by listening to the sound, etc. due to the reflection of sound. By using a directional speaker that is characteristic of the sound attenuation of sound is straight to solve this problem and obtain feedback on measures that can effectively provide the oocytes to a valid information on a disaster situation and the evacuation.

• Journal of the Institute of Convergence Signal Processing
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• v.15 no.3
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• pp.91-96
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• 2014

For Sound source direction and separation method, Frequency Domain Binaural Model(FDBM) shows low computational cost and high performance for sound source separation. This method performs sound source orientation and separation by obtaining the Interaural Phase Difference(IPD) and Interaural Level Difference(ILD) in frequency domain. But the problem of reflection occurs in practical environment. To reduce this reflection, a method to simulate the sound localization of a direct sound, to detect the initial arriving sound, to check the direction of the sound, and to separate the sound is presented. Simulation results show that the direction is estimated to lie close within 10% from the sound source and, in the presence of the reflection, the level of the separation of the sound source is improved by higher Coherence and PESQ(Perceptual Evaluation of Speech Quality) and by lower directional damping than those of the existing FDBM. In case of no reflection, the degree of separation was low.

• The Journal of the Acoustical Society of Korea
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• v.37 no.5
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• pp.323-330
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• 2018

This study investigated effects of absorbent gypsum board in the ceiling on low-frequency heavyweight floor impact sound through sound absorption coefficient and floor impact sound measurement. The sound absorption coefficients were measured with sound absorbent gypsum board, glass wool on gypsum board, and a double panel absorbent gypsum board (absorbent gypsum board + glass wool + absorbent gypsum board). Result showed that the absorbent gypsum board had sound absorption coefficient of 0.1 ~ 0.7 from 200 and 630 Hz octave band. The sound absorption coefficient was increased in all frequency range by adding glass wool. Additional absorbent gypsum board increased sound absorption coefficient up to 250 Hz octave band, but decreased over 250 Hz. Heavyweight floor impact sounds were measured in test building for three materials above, gypsum board, and bare slab. Result showed that glass wool on gypsum board and a double panel absorbent gypsum board reduced by 3 dB ~ 4 dB (single number quantity) heavyweight floor impact sound. Comparing with bare slab condition, floor impact sound reduction was mainly found from 125 Hz to 500 Hz octave band, and the maximum reduction was shown in the 250 Hz octave band.

• The Journal of the Acoustical Society of Korea
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• v.17 no.7
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• pp.22-27
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• 1998

본 논문에서는 ETRI에서 개발한 가변 어휘 음성 인식기의 어휘 독립 음향 모델링 방법을 기술하고, 이 모델의 어휘 종속, 어휘 독립 및 어휘적응 성능을 평가하기 위하여 다 양한 고립단어 및 연속음성 DB에 대하여 실험한 결과를 분석하였다. 평가를 위하여 사용한 음성 DB로는 고립단어 음성으로 POW(Phonetically Optimized Words) 3848, PBW(Phonetically Balanced Words) 445, PBW 452, 호텔예약 244 단어, 게임 제어용 단어 등이며, 연속음성으로 일반 문장 음성 및 연속 숫자음을 이용하였다. 성능 분석 결과 40개 음소 모델만으로도 비교적 높은 인식률을 보여 주었지만, 어휘독립의 경우는 어휘종속에 비 하여 성능이 크게 낮았고, 특히 대상 어휘가 숫자음, 알파벳, 연속음 등의 경우에는 POW 데이터나 PBW 데이터만 가지고는 우수한 가변 어휘 음성 인식기를 구현하기에 한계가 있 음을 알 수 있다. 또한, 훈련 데이터의 어휘와 평가데이터의 어휘가 비슷할 경우에는 변이음 모델을 사용하면 음소 모델만을 사용할 경우에 비하여 그 성능이 우수하였지만, 일반적인 어휘독립의 상황에서는 효과가 별로 없음을 알 수 있었다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.531-534
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• 2004

음장 재생기는 인공잔향기의 일부로 알려져 있었으나 실제로는 다른 접근 방법이 필요하다. 인공잔향기의 용도가 대체로 무향에 가까운 음원에 인공잔향을 가해주는 것이라면, 음장 재생기는 청취자에게 넓은 공간감을 위해 이미 잔향이 가해진 음원에 초기반사음만을 가해주기 때문이다. 본 논문에서 제안하는 음장재생기는 모사하고자 하는 공간의 충격응답에서 직접음 대비 반사음의 세기를 조절하여 sound coloration을 줄이고, 초기반사음의 패닝을 이용하여 넓은 공간감을 효과적으로 재생한다. 또한 본 음장재생기는 ITDG, LEF, Stage width, Room size, Liveness 등의 객관적 인자들을 조정할 수 있기 때문에 원하는 공간의 모사뿐 아니라 가상공간의 크기와 느낌을 변화시킬 수 있다.