• 한국해양공학회지
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• 제22권1호
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• pp.30-36
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• 2008

Underwater ambient noise originating from geophysical, biological, and man-made acoustic sources contains information on the source and the ocean environment. Such noise affectsthe performance of sonar equipment. In this paper, three steps are used to identify the ambient noise source, detection, feature extraction, and similarity measurement. First, we use the zero-crossing rate to detect the ambient noisesource from background noise. Then, a set of feature vectors is proposed forthe ambient noise source using the Hilbert-Huang transform and the Karhunen-Loeve transform. Finally, the Euclidean distance is used to measure the similarity between the standard feature vector and the feature vector of the unknown ambient noise source. The developed algorithm is applied to the observed ocean data, and the results are presented and discussed.

• Ocean Science Journal
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• 제41권3호
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• pp.175-179
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• 2006

The Ieodo Ocean Research Station(IORS) is an integrated meteorological and oceanographic observation base which was constructed on the Ieodo underwater rock located at a distance of about 150 km to the south-west of the Mara-do, the southernmost island in Korea. The underwater ambient noise level observed at the IORS was similar to the results of the shallow water surrounding the Korean Peninsula (Choi et al. 2003) and was higher than that of deep ocean (Wenz 1962). The wind dependence of ambient noise was dominant at frequencies of a few kHz. The surface current dependence of ambient noise showed good correlation with the ambient noise in the frequency of 10 kHz. Especially, the shrimp sound was estimated through investigations of waveform and spectrum and its main acoustic energy was about 40 dB larger than ambient noise level at 5 kHz.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.943-945
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• 2006

The experiment on study of ambient nose generated by large-amplitude internal waves in Luzon Strait is analyzed. Simultaneous observations of internal waves and characteristics of ambient noise generated by them were carried out. Fast 50-m solitary internal wave propagated to the northwest direction with speed more than 3 m/s was observed. It was revealed an enhancing of ambient noise level (at frequency range 1-2 kHz) at a time of passing the face side of the solitary wave.

• 한국산학기술학회논문지
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• 제8권5호
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• pp.1062-1068
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• 2007

변압기 보호와 과전류를 막기 위한 목적으로 COS를 사용하고 있다. 그러나 COS 휴즈는 과전류가 흐르면 과부하에 의하여 용단되면서 강한 아크를 발생하여 공기 절연파괴를 일으킨다. 이러한 현상은 소음을 발생하면서 주변 거주자나 행인들에게 두려움을 준다. 그래서 실제 환경하에서 발생되는 소음을 시급히 정립할 필요가 있다. 본 논문은 COS 휴즈가 용단되면서 발생하는 충격성 소음의 특성을 파악하고 이러한 소음을 줄일 수 있는 방안을 제안한다.

• Ocean and Polar Research
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• 제28권4호
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• pp.459-465
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• 2006

Ambient noise as a background noise in the ocean has been well known for its the various and irregular signal characteristics. Generally, these signals we treated as noise and they are analyzed through stochastical level if they don't include definite sinusoidal signals. This study is to see how ocean ambient noise can be analyzed by the chaotic analysis technique. The chaotic analysis is carried out with underwater ambient noise obtained in areas near the Korean Peninsula. The calculated physical parameters of time series signal are as follows: histogram, self-correlation coefficient, delay time, frequency spectrum, sonogram, return map, embedding dimension, correlation dimension, Lyapunov exponent, etc. We investigate the chaotic pattern of noises from these parameters. From the embedding dimensions of underwater noises, the assesment of underwater noise by chaotic analysis shows similar results if they don't include a definite sinusoidal signal. However, the values of Lyapunov exponent (divergence exponent) are smaller than that of random noise signal. As a result we confirm the possibility of classification of underwater noise using Lyapunov analysis.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2006년도 추계학술발표논문집
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• pp.176-179
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• 2006

We are using COS to purpose blocking the excess current and to protect the transformer. But the fuse of COS is melt due to the overload if the excess current flows and it destroy an air severing relations to clear as strong arc happens. Such phenomenon induces an impact ambient noise and it gives the circumstance area resident or pedestrian the fear. Thus, We are the actual circumstances which an ambient noise countermeasure establishment have desired urgently. In this study, we grasp the characteristic of an impact ambient noise which a COS fuse happens the melting and study the method to reduce an impact ambient noise.

• 한국음향학회지
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• 제22권3호
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• pp.233-241
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• 2003

한반도의 연근해에서 9년간 ('90∼'98)에 걸쳐 200m이내의 수심을 보이는 13개 정점에서 배경소음을 측정한 자료를 환경별로 통계 처리하여 소음준위를 분석하였다. 주파수 스펙트럼은 1/3옥타브 밴드의 중심주파수 25㎐부터 20㎑까지 분석하였다. 분석결과, 대양의 배경소음스펙트럼으로 알려진 Wenz의 결과와는 다소간의 차이를 보여주었다. 연근해에서 측정된 결과는 다양한 선박활동 및 연안소음, 파도의 영향 등으로 인해 같은 조건에서의 대양의 결과 보다 높은 배경소음준위를 보이고 있었으며, 통계분석에 근거하여 천해 소음 추정식을 산출하였다.

• 한국정보통신학회논문지
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• 제7권6호
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• pp.1123-1129
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• 2003

기동하는 잠수함이나 함정 등의 방사 소음 특성은 토날 신호와 광대역 배경잡음으로 구분될 수 있다. 토날 신호는 함정의 모터나 엔진 등의 회전으로 인해 발생하는 것이고, 광대역 배경잡음은 프로펠러에 의해 방사된 기포와 선체의 주위 물의 흐름 등으로 인해 발생하는 것이다. 이와 같은 기동함정의 방사 소음의 토날 신호와 배경 잡음을 분석하면 함정의 종류나 속도 등에 대한 정보를 분석할 수가 있다. 이 때 배경잡음의 세기가 토날 신호에 비하여 큰 경우는 토날 신호를 배경잡음으로부터 분리하기가 쉽지 않다. 본 연구에서는 ATW(Automatic Tracking Window) 전처리 알고리즘을 이용하여 방사 소음의 방향을 탐지하고, 표적 방향으로 배열 센서의 빔을 형하여 신호를 채취한다. 또한 ATW 알고리즘을 이용하여 이 신호에서 광대역 잡음에 섞여 있는 미약한 토날 신호를 분리할 수 있는 방법을 제시한다.

• Structural Engineering and Mechanics
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• 제59권1호
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• pp.187-207
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• 2016

Practical ambient excitations of engineering structures usually do not comply with the stationary-white-noise assumption in traditional operational modal analysis methods due to heavy traffic, wind guests, and other disturbances. In order to eliminate spurious modes induced by non-white noise inputs, the improved stochastic subspace identification based on a delay index is proposed in this paper for a representative kind of stationary non-white noise ambient excitations, which have nonzero autocorrelation values near the vertical axis. It relaxes the stationary-white-noise assumption of inputs by avoiding corresponding unqualified elements in the Hankel matrix. Details of the improved stochastic subspace identification algorithms and determination of the delay index are discussed. Numerical simulations on a four-story frame and laboratory vibration experiments on a simply supported beam have demonstrated the accuracy and reliability of the proposed method in eliminating spurious modes under non-white noise ambient excitations.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2003년도 정기총회 및 추계학술대회
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• pp.89-93
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• 2003

The ambient noise in modem society is the factor to give people serious influence. Noise barriers installation is mostly used in the apartment estate to protect countermeasure about the road traffic ambient noise. The purpose of this study is to suggest reference data fur design of traffic noise reduction in apartment estate. It finds out how the traffic noise is measured about a noise barriers and physical characteristics. The 57dB was measured from the noise barriers in a 2m point. An ambient noise's of the part to belong noise attenuation is big at the sound arresting area of the noise barriers as the distance far.