• 대한조선학회논문집
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• 제61권1호
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• pp.1-7
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• 2024

Underwater sound speed is an important analysis parameter on an estimation of the underwater radiated noise (URN) emitted from vessels. This paper aims to present an underwater sound speed measurement procedure using a cross-correlation of time-domain acoustic signals and validate the procedure through an experiment in a reverberant water tank. For the purpose, time-domain acoustic signals transmitted by a Gaussian pulse excitation from an acoustic projector have been measured at 20 hydrophone positions in the reverberant water tank. Then, the sound speed in water has been calculated by a linear regression using 190 cross-correlation cases of distances and time lags between the received signals and the result has been compared with those estimated by the existing empirical formulae. From the result, it is regarded that the presented experimental procedure to measure an underwater sound speed is reliably applicable if the time resolution is sufficiently high in the measurement.

• 센서학회지
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• 제32권3호
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• pp.199-206
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• 2023

This study presents a novel monitoring technique for underwater high-voltage direct current (HVDC) cables based on the Distributed Acoustic Sensor (DAS). The proposed technique utilizes vibration and acoustic signals generated on HVDC cables to monitor their condition and detect events such as earthquakes, shipments, tidal currents, and construction activities. To implement the monitoring system, a DAS based on phase-sensitive optical time-domain reflectometry (Φ-OTDR) system was designed, fabricated, and validated for performance. For the HVDC cable monitoring experiments, a testbed was constructed on land, mimicking the cable burial method and protective equipment used underwater. Defined various scenarios that could cause cable damage and conducted experiments accordingly. The developed DAS system achieved a maximum measurement distance of 50 km, a distance measurement interval of 2 m, and a measurement repetition rate of 1 kHz. Extensive experiments conducted on HVDC cables and protective facilities demonstrated the practical potential of the DAS system for monitoring underwater and underground areas.

• 한국군사과학기술학회지
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• 제6권2호
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• pp.45-54
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• 2003

The radiated-noise of combat ship is very important in the point of detection and vulnerability assessment. Therefore several kind of underwater acoustic measurement method has been developed. This paper reviews the various measurement concepts and proposes a procedure to select the better one under consideration of measurement conditions. And this paper recommends the portable drift type, which has vertical line array, as the most efficient measurement method in Korean sea.

• 한국군사과학기술학회지
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• 제6권2호
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• pp.55-64
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• 2003

Underwater acoustic noise measurement is an essential element for vulnerability assessment of modern naval platforms. But during the last few decades environmental conditions have drastically changed due to the gradually increasing sea ambient noise level and decreasing submarine radiated noise level. A real-time underwater acoustic measurement system with vertical line array is designed for the quiet submarine radiated noise assessment in challenging environment. This system has a constant directivity index in measurement frequency range and accurate tracking capability for the transmission loss compensation and navigation aids inside the submarine. This system has been validated at sea and used several times for the submarine noise measurement.

• 한국소음진동공학회논문집
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• 제25권11호
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• pp.747-752
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• 2015

Underwater radiated noise is an important characteristic in the naval weapon systems. It is difficult to measure the radiation efficiency of underwater vehicle, such as UUV(unmanned underwater vehicle) and underwater weapons in real operation environment. In this study, acoustic radiation efficiency of a circular cylindrical structure is measured in the laboratory-water tank. The radiation efficiency is compared with the numerical results and it is found that they are in a good agreement. Therefore, the measurement method can be applied effectively for predicting the underwater radiation noise and effectiveness of radiation reduction means.

• 대한조선학회논문집
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• 제56권5호
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• pp.464-471
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• 2019

The acoustic power is a major acoustical characteristic of an underwater vehicle and could be measured in a reverberant water tank. In order to obtain accurate measurement results, the acoustic field formed by the sound source should be investigated quantitatively in the reverberant water tank. In this research, the acoustic field of a reverberant water tank containing an underwater sound source has been analyzed by using an acoustic radiosity method one of the numerical analysis methods suitable for the acoustic analysis of the highly diffused space. The source level of the underwater sound source and acoustical properties of the water tank input to the numerical analysis have been estimated by applying the reverberant tank plot method through a preliminary experiment result. The comparison of the numerical analysis result with that of the experiment has verified the accuracy of the acoustic radiosity method.

• 로봇학회논문지
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• 제12권4호
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• pp.402-410
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• 2017

Acoustic based localization is essential to operate autonomous robotic systems in underwater environment where the use of sensorial data is limited. This paper proposes a localization method using artificial underwater acoustic sources. The proposed method acquires directional angles of acoustic sources using time difference of arrivals of two hydrophones. For this purpose, a probabilistic approach is used for accurate estimation of the time delay. Then, Gaussian sum filter based SLAM technique is used to localize both acoustic sources and underwater vehicle. It is performed by using bearing of acoustic sources as measurement and inertial sensors as prediction model. The proposed method can handle directional ambiguity of time difference based source localization by generating Gaussian models corresponding to possible locations of both front and back sides. Through these processes, the proposed method can provide reliable localization method for underwater vehicles without any prior information of source locations. The performance of the proposed method is verified by experimental results conducted in a real sea environment.

• 한국군사과학기술학회지
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• 제4권2호
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• pp.84-96
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• 2001

Test data for a naval vessel is massive, expensive and impossible to be retested in a underwater acoustic measurement on the same condition. So, it is very important. In this paper, I mention massive underwater acoustic multimedia database system that was developed to store a long time, manage systematically, supply raw data and analyze data to user in 2-tier structure. Also, I propose 3-tier structure to extend the current database system that can supply multimedia data.

• 한국정보통신학회논문지
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• 제5권1호
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• pp.212-221
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• 2001

본 논문에서는 수중에서의 초음파를 이용하여 개발되고 있는 시스템 및 핵심기술들의 시험을 위해 반드시 필요한 무향수조 설계에 대하여 기술하고 있다. 무향수조에 사용되는 흡음판의 재질로서는 일반적으로 다공성 플라스틱, 재생용 고무, 알루미늄 폼, 우레탄 폼 등을 사용하는데, 본 논문에서는 흡음성능이 우수하고 경제적인 다공생 재생고무를 선정하였다. 따라서, 이 재질에 대한 흡음성능 및 특성을 살펴보았다. 또한, 흡음판의 형상설계를 통해 최적의 흡음성능을 갖는 무향수조를 설립할 수 있도록 쐐기형 흡음판을 설계하였으며, 쐐기각도에 따른 반사경로를 수학적으로 해석하여 최적의 흡음성능을 가질 수 있는 흡음판을 설계하였다. 또한, 확보된 무향수조 공간에 효율적인 흡음판 배치를 위한 치구설계 및 배치선계를 수행하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2000년도 춘계종합학술대회
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• pp.371-377
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• 2000

본 논문에서는 수중에서의 초음파를 이용하여 개발되고 있는 시스템 및 핵심기술들의 시험을 위해 반드시 필요한 무향수조 설계에 대하여 기술하고 있다. 무향수조에 사용되는 흡음판의 재질로서는 일반적으로 다공성 플라스틱, 재생용 고무, 알루미늄 폼, 우레탄 폼 둥을 사용하는데, 본 논문에서는 흡음성능이 우수하고 경제적인 다공생 재생고무를 선정하였다. 따라서, 이 재질에 대한 흡음성능 및 특성을 살펴보았다. 또한, 흡음판의 형상설계를 통해 최적의 흡음성능을 갖는 무향수조를 설립할 수 있도록 쐐기형 흡음판을 설계하였으며, 쐐기각도에 따른 반사경로를 수학적으로 해석하여 최적의 흡음성능을 가질 수 있는 흡음판을 설계하였다 또한, 확보된 무향수조 공간에 효율적인 흡음판 배치를 위한 치구설계 및 배치설계를 수행하였다.