• 한국음향학회지
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• 제13권1호
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• pp.49-56
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• 1994

해앙에서 강우에 의하여 발생된 수중잡음의 특성을 밝히기 위하여 한국 동해의 연안에서 비가 내리는 동안 해수중 주위잡음을 측정하였다. 수심 200 m인 정점에서 세 개의 수중청음기를 각각 수심 30 m, 50 m및 100 m에 설치하였다. 먼저 강우상도가 1.5~23.4 mm/h일 때 강우잡음의 스펙트럼 특성을 주의깊게 조사하였다. 그리고 다양한 주파수에 있어서 스펙트럼레벨과 강우강도와의 관련을 조사하였다. 또한, 수중청음기로 수신한 강우잡음의 파형을 관찰하여 강우에 의한 수중잡음의 발생기구에 대하여 고찰하였다.

• 융합신호처리학회논문지
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• 제4권3호
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• pp.15-20
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• 2003

핸즈프리 마이크를 이용한 원격회의나 원격 통신 시스템과 같은 몇 가지의 응용분야에서, 음성 신호는 주위 잡음뿐만 아니라 마이크와 스피커사이의 결합에 의해 발생하는 에코에 의해서 왜곡되기 쉽다. 게다가 채널 왜곡이나 부가적인 잡음을 포함한 환경 잡음들은 원래의 입력 음성신호에 영향을 미치리라 고려된다. 본 논문에서는, 이러한 핸즈프리 음성에 있어서의 음성 인식률을 향상시키기 위해 에코 제거기와 최대 사후 추정(MAP)을 이용한 새로운 접근방식을 소개한다. 이 접근방식에서, 제안된 시스템이 에코를 포함한 주위 잡음 환경에서의 핸즈프리 음성인식에 효과적이라는 것을 보여준다 또한, 실험 결과는 에코 제거기와 MAP 환경적응 기술의 결합 시스템이 에코와 잡음 환경에 잘 적응하는 것을 보여준다.

• 한국소음진동공학회논문집
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• 제20권4호
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• pp.338-347
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• 2010

Heunginjimun designated as a Treasure No.1 is a two-story wooden structure with 5 bay and 2 bay in its front and side views, respectively. This paper presents an investigation on vibration characteristics of Heunginjimun through both ambient vibration and impact hammer tests. Ambient vibration test was performed to identify the natural frequency of Heunginjimun from the spectrum analysis of time history. Impact hammer test was undertaken to find the frequency of Heunginjimun which is affected by the surrounding traffics and to verify the reciprocal principle for the wooden structural system. Ambient vibration test results of Heunginjimun showed that the natural frequencies in two principal axes 1.5 Hz and 1.1 Hz, respectively. It was confirmed from impact hammer tests for a ground that the frequency of 4.2 Hz is caused by the traffics surrounding Heunginjimun. It was also observed that from the impact hammer test results between two locations in Heunginjimun that the transfer functions measured from two corresponding locations coincided well with each other. This result shows that the wooden structural system is globally linear, and the reciprocal principle is established.

• 한국통신학회논문지
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• 제40권10호
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• pp.2062-2064
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• 2015

본 논문에서는 LED 패널의 신호를 받아 모바일 단말기에 장착된 이미지 센서를 통하여 임의의 위치에 있는 모바일 단말기의 위치를 추정하는 실내 측위 알고리즘을 제안하였다. 측위 성능평가를 위하여 실내에 존재하는 잡음 환경을 고려하였고, 제안한 알고리즘은 잡음환경에 무관하게 높은 측위 성능을 보임을 입증하였다.

• 수산해양기술연구
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• 제35권1호
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• pp.19-24
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• 1999

This paper is second part on the auditory thresholds and fish behaviors to the underwater sounds for luring of target species at the set-net in the coast of Cheju. In order to obtain the critical ratio of yellow tails(Seriola quinqueradiata) and the emission level of underwater sound for luring of them, we make experiments to measure the auditory threshold of them using conditioning with electric shock. In state that the white noise with 10dB higher sound pressure level than ambient noise is emitted, the auditory thresholds of yellow tails are measured with 100~116.5dB and they are higher than those in state of no emission of white noise by the masking effects of it. Although sound pressure level of background noise go down, the auditory thresholds go up with frequency above than 300Hz.The critical ratio of yellow-tails in frequency of 80Hz, 100Hz, 200Hz, 500Hz, 800Hz are 46dB, 40dB, 50dB, 52dB, 60dB, 70dB respectively. The sound pressure level of which the signal sound is recognized by yellow tails under the ambient noise is above 100dB and the critical ratio of them is above 40dB.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.547-548
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• 2009

• 대한전자공학회논문지SP
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• 제47권1호
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• pp.175-182
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• 2010

본 논문에서는 배경 잡음 환경에서 배경 잡음에 의해 저하된 음성 신호의 명료도를 soft decision 기반의 음성 부재 확률을 이용하여 음성 강화 이득을 수정함으로써 음성의 명료도를 보다 향상시키는 기법을 제안한다. 배경 잡음 환경에서 저하된 음성의 명료도를 향상시키기 위한 기존의 음성 강화 기법으로써 soft decision을 이용하여 오염된 음성 신호로부터 깨끗한 음성 신호만 증폭시키는 알고리즘이 제안되었다. 기존의 음성 강화 기법 보다 음성 구간과 비음성 구간 및 전이 구간에서 강인한 음성 강화 이득을 추정하기 위하여 soft decision 기반의 음성 부재 확률 (Speech Absence Probability)을 음성 강화 이득에 통합한 음성 강화 이득 수정 알고리즘을 제안한다. 제안된 음성 강화 기법의 성능은 다양한 배경 잡음 환경에서 ITU-T P.800의 주관적인 음질 측정 방법인 (Comparison Category Rating) 테스트에 의해서 평가되었으며, 기존의 음성 강화 기법과 비교하여 향상된 성능을 보여주었다.

• 수산해양기술연구
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• 제22권3호
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• pp.36-41
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• 1986

Uederwater ambient noise was measured at the set net in the Neung-Po Eay. The environment characteristics depend upon oceanographic conditions of sound propagation and its implication on the source of ambient noise. The results of measurement and analysis were as follows: 1. The frequency of the maximum noise level of two passenger. vessels was around 300 Hz. The spectrum level of the fast vessel (the Air-Ferry) was lower than the little slow vessel (the Olympic) between 50-150 Hz in frequences. 2. The spectrum level of the surface in the playground of the set net was lower than the deeper water till 500 Hz, but over that frequency the level was getting lower as the depth was deep. 3. The spectrum level outside the bag of the set net was greater than the inside between 50 and 700 Hz, but over 1,500 Hz the level inside the bag was higher than the outside. 4. The spectrum level of the outside of the breeding tank was higher than the inside in the daytime. However at night opposite phenomenon occurs.

• Smart Structures and Systems
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• 제14권3호
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• pp.367-376
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• 2014

Ambient vibration techniques are nowadays a very popular tool to assess dynamic properties of buildings. Due to its non destructive character, this method is particularly valuable, especially for health monitoring of historical monuments. The present ambient vibration experiment consists on the evaluation of vibration modes of a Medieval tower. Situated in Soncino (close to Cremona, in the Northern Italian region named Lombardia), the tower of 41.5 meters height has been monitored by seismometers located at different points inside the structure. Spectral ratios of the recorded ambient vibrations clearly identify a fundamental mode at about 1 Hz, with a slight difference in the two horizontal components. A second mode is also evidenced at approx 4-5 Hz, with a moderate degree of uncertainty. The records of a ML 4.4 earthquake, occurred during the monitoring period, confirm the information obtained by microtremor analysis. Daily variations of both 1st and 2nd mode were detected: these variations, of an amount up to 2%, seem to be well related with the temperature.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 봄 학술발표회 논문집
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• pp.291-300
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• 1998

This paper demonstrates how ambient vibration measurements at a limited number of locations can be effectively utilized to estimate parameters of a finite element model of a large-scale structural system involving a large number of elements. System identification using ambient vibration measurements presents a challenge requiring the use of special identification techniques, which ran deal with very small magnitudes of ambient vibration contaminated by noise without the knowledge of input farces. In the present study, the modal parameters such as natural frequencies, damping ratios, and mode shapes of the structural system were estimated by means of appropriate system identification techniques including the random decrement method. Moreover, estimation of parameters such as the stiffness matrix of the finite element model from the system response measured by a limited number of sensors is another challenge. In this study, the system stiffness matrix was estimated by using the quadratic optimization involving the computed and measured modal strain energy of the system, with the aid of a sensitivity relationship between each element stiffness and the modal parameters established by the second order inverse modal perturbation theory. The finite element models thus identified represent the actual structural system very well, as their calculated dynamic characteristics satisfactorily matched the observed ones from the ambient vibration test performed on a large-scale structural system subjected primarily to ambient wind excitations. The dynamic models identified by this study will be used for design of an active mass damper system to be installed on this structure fer suppressing its wind vibration.