• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.1
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• pp.119-124
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• 2022

Successful underwater localization requires a large-scale, parallel computing environment that can be mounted on various underwater robots. Accordingly, we propose a design method for an artificial intelligence computing platform for underwater localization. The proposed platform consists of a total of four hardware modules. Transponder and hydrophone modules transmit and receive sound waves, and the FPGA module rapidly pre-processes the transmitted and received sound wave signals in parallel. Jetson module processes artificial intelligence based algorithms. We performed a sound wave transmission/reception experiment for underwater localization according to distance in an actual underwater environment. As a result, the designed platform was verified.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.16 no.2
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• pp.69-76
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• 1980

This paper describes the measurement of the underwater noises produced by the engine vibration around the engine room of stern trawler MIS Sae-Ba-Da(2275GT, 3,600 PS) and pole kner M/S Kwan-Ak-San (243 GT, 1000 PS) while the ship is stopping. The underwater noise pressure level was measured with the underwater level meter of which measuring range is 100 to 200 dB(re bLPa). A and B denotes the maximum pressure level measured at right beneath the bottom of the engine room, while the main engine of the Sae-Ba-Da revoluted at 750 and 500 rpm, respectively. C denotes that of the main engine of the Kwan-Ak-San revoluted at 350 rpm, and D that of the generator of the Sae-Ba-Da revoluted at 720 rpm. Thus A, B, C and D were set for the standard sound source for the experiment. The results obtained are as follows: 1. The noise Pressure level at A, B, C and D were 170.5,165,153 and 158dB, respectively. 2. When the check points distanted vertically 1, 10, 20, 30, 40, 50m from the sound source, the underwater noise presure levels were 170.5, 155, 148, 144 and 138 dB and the directional angle was 116\ulcorner in case of A. 3. The sound level attenuated at the rate of 20dB per 10" meters of the horizontal distance from the sound sources. 4. The frequency distribution of the noise was 100Hz to 10KHz and predominant frequency was 700 to 800Hzminant frequency was 700 to 800Hz

• Journal of the Society of Naval Architects of Korea
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• v.59 no.6
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• pp.362-371
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• 2022

As considerable interests in noise emission from the ships have been increased, International Maritime Organization (IMO) standardized the Underwater Radiated Noise (URN) measurement process of commercial ships in deep seas by enacting the related ISO standard ISO 17208-1 and classification societies responded with the enactment or revision of corresponding notations. According to this trend, a new hybrid underwater sound propagation model based on underwater sound propagation theories was developed and its accuracy on analysis was verified through the result comparison with the results of other generally used models. Using the verified model, each URN propagation characteristics adjusted by the correction methods proposed in the ISO standard and class notations were analyzed and compared in two assumed URN measurement cases. The results showed that the effects of transmission loss corrections in the circumstances with less bottom reflections generally similar but they had rather large differences in the model analysis results with bottom-reflection-dominant conditions. It was concluded that the deep consideration of effective bottom-reflection-correction method should be made in future revisions of ISO standard and class notations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.9
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• pp.928-934
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• 2009

Underwater impulsive sound such as underwater blasting noise, piling noise and stone breaking hammer affects marine animal hearing response and organs. This study describes the characteristics of various impulsive noise from waterfront construction site and their effect on fish. Time constant, peak pressure, energy and SEL(sound exposure level) of four different underwater impulsive sounds are quantified. Auditory and non-auditory tissue damage ranges are derived by comparing their quantities to the exposure criteria for fish. Damage ranges of auditory tissue and non-auditory tissue of underwater boring blast of 150 kg of charge, are about 100 m and 300 m, respectively. Other three impulsive sounds also gives damage effects but less than that of underwater boring blast.

• The Journal of the Acoustical Society of Korea
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• v.40 no.3
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• pp.183-191
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• 2021

A time-series variation of temperature, salinity, and underwater sound speed was analyzed using an Array for Real-time Geostrophic Oceanography (ARGO) float which autonomously collects temperature and salinity for about 10month with 2 days cycle among 12 floats in the center of the Yellow Sea. As a result, the underwater sound channel appeared below the thermocline as the surface sound channel, which is dominant in the winter season, reduced in April. Besides, for a certain time in the spring season, the sound ray reflected the sea surface frequently due to the short-term temperature inversion effect. Based on the case of successful observation of ARGO float in the shallow water, using prolonged monitoring unmanned platform may contribute to predicting sound transmission loss if the temperature inversion and sound channel including background environment focusing are investigated in the center of the Yellow Sea.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.769-773
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• 2001

In order to obtain the fundamental data on the underwater sound of fishes for marine ranching. The underwater sound of Red Seabream(Pagrus major) and Schlegel's black rockfish(Sebastes schlegeli) were measured, which character were summarized by FFT analysis.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.4
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• pp.52-61
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• 2007

Temporal and spatial variations of sea water largely affect on the pattern of underwater sound propagation. Acoustic environmental changes and their effects on underwater sound propagation in the northern part of the East Sea, which have been poorly studied mainly due to lack of observations, are investigated by analyzing the hydrographic data acquired since 1993. Severe changes in acoustic environments are associated with various physical processes such as deep convection, thermal fronts, and eddies in the northern part of the East Sea. Spatio-temporal variations of sound speed field and the layer of the maximum sound speed are categorized into six typical cases. Using a sound source of 5 kHz, acoustic transmission losses are calculated range-independently for the six typical cases. Significant differences among the patterns of transmission loss in the six cases suggest that a different tactics are required when we operate in the northern part of the East Sea.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.617-621
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• 1998

Optical sensing techniques have been associated with high sensitivity and precise measurements and attracted considerable attention in recent years. In this paper, two channels TDM(Time Division Multiplexing) fiber-optic hydrophone array for the underwater applications was fabricated and their acoustic characteristics were investigated by using the acoustic water tank. A fiber length of the order of 100m is wounded at the hollow cylinder type aluminum mandrel. An unbalanced interferometer (discrete Mach-Zehnder type) was used. Sound detection performance is tested in the underwater tank with 2kHz continuous sound source. Finally, it is shown that two channels TDM(Time Division Multiplexing) fiber-optic hydrophone array can detect 2kHz sound stably.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.3
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• pp.142-146
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• 2007

Ambient noise was measured for 3 hours on May, 2001 at a site of 20 m water depth in the Korean coast of the Yellow Sea. During the measurement, the strong underwater sound assuming by marine life was continually observed. The spectrum level of this sound was very high compared to that of underwater ambient noise over the frequency range from 1 to 20 kHz. Therefore, this underwater sound can continually affect the ambient noise level. In this study, the source of the underwater sound was investigated. The snapping shrimp was estimated as reliable source. It was confirmed through comparison with experimental results described in previously literatures. It was also confirmed through analysis of snapping shrimp sound measured under laboratory conditions.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.1
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• pp.50-58
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• 1996

The authors carried out a field experiment to confirm the effect of underwater sound on the luring of fish schools in a setnet in the coast of Cheju Island. The effects of the acoustic emission on the luring of fish schools were observed using a manufectured underwater speaker in the setnet, and pure sound, of which frequency was 600Hz and the source level was 126dB, was emitted on and off at 5 minutes intervals in the set net during the night of ,July 29 and ,July 31. So we had recorded behavior of fish schools by the telesounder with two channel and shape of the setnet by underwater video camera and analyzed them. When the flood and ebb currents were around the setnet, the nets rised to the surface of water and it happened occasionaly at the stand of tide. Therefore, it was in the state that fish schools feel constraint to enter into the setnet, and was required a new design of the setnet stand up to strong tidal current. As the pure sound, of which frequency was 600Hz was emitted for the luring of fish schools in a setnet, the catch ammounts of fish, the young horce mackereWI'rachllrlls japonicus), was increased 4~6 times than not emitted.