• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.1
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• pp.32-38
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• 2022

In this study, Target strength for multi-frequency (38 kHz, 70 kHz, 120 kHz and 200 kHz) of chub mackerel (Scomber japonicus) was estimated using by the KRM model. The body shape of the Chub mackerel was described by an X-ray system and the body length of 20 individuals ranged from 16 cm to 28 cm. The swimbladder tilt angle ranged between -8 and -14°, the maximum TS value according to the swimming angle of chub mackerel was -33.0 dB at -11°. The averaged TScm according to fork length was -66.02 dB at 38 kHz, -66.50 dB at 70 kHz, -66.00 dB at 120 kHz and -67.35 dB at 200kHz, respectively.

• The Journal of the Acoustical Society of Korea
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• v.35 no.5
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• pp.331-339
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• 2016

This paper suggests an estimation method of the source signal and the channel impulse response (CIR) using ray-based blind deconvolution (RBD) in the underwater acoustic channel environment where Doppler effect exists by the relative motion between source and receiver. It is difficult to estimate the CIR on Doppler effect by the matched filter with a highly Doppler-sensitive waveform such as the m-sequence signal because Doppler shift can severely degrade the correlation between the received signal corrupted by Doppler effect and the original source signal. In this study, the Doppler-shifted source-signal's phase is estimated using the RBD, and the received signal is compensated by it to obtain the Doppler-corrected CIR. It is verified that using the matched filter with the received signal from the experimental data fails to estimate the CIR while the obtained CIR by the suggested method has the similarity to the propagation path of the ray model. Also, the results show that the reconstructed source signal using the RBD has the better Doppler shift compensation than the Doppler-shifted source signal derived from scattering function.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.2
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• pp.152-159
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• 2017

Rockfish was a commercially important fish specie in marine ranching areas in Korea. To estimate density and biomass of rockfish using acoustic method, target strength (TS) information is required on the species. This study measured TS dependence on tilt angle and size on 14 live rockfish individuals at 38, 70, and, 120 kHz by ex-situ measurement (tethered method) and acoustic scattering model (Krichhoff ray mode, KRM). The swimbladdered angle ranged from 18 to $30^{\circ}$ ($mean{\pm}s.d.=26{\pm}4^{\circ}$). The mean TS for all individuals was highest -35.9 dB of tilt angle $-17^{\circ}$ at 38 kHz, -35.4 dB of tilt angle $-25^{\circ}$ at 70 kHz, and -34.9 dB of tilt angle $-22^{\circ}$ at 120 kHz. The ex-situ TS-total length (TL, cm) relationships were $TS_{38kHz}=20log_{10}(TL)-67.1$, $TS_{70kHz}=20log_{10}(TL)-68.6$, and $TS_{120kHz}=20log_{10}(TL)-69.9$, respectively. The model TS-total length (TL, cm) relationships were $TS_{38kHz}=20log_{10}(TL)-66.4$, $TS_{70kHz}=20log_{10}(TL)-67.0$, $TS_{120kHz}=20log_{10}(TL)-67.0$. The two measurements between the ex-situ TS and KRM model for TS-tilt angle and fish size were found to be significantly correlated.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.3
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• pp.424-431
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• 2015

This study was focused on acoustic scattering characteristics of jack mackerel (Trachurus japonicus) at frequency 38, 70, and 120 kHz by Kirchhoff-ray mode (KRM) model. The body length (BL) of 16 individuals ranged in 12.2~22.0 cm ($mean{\pm}S.D.$: $17.8{\pm}3.2cm$) and the swimbladder length ranged in 4.2~8.6 cm ($mean{\pm}S.D.$: $6.6{\pm}1.6cm$) and the swimbladder cross section ranged in $1.7{\sim}6.6cm^2$ ($mean{\pm}S.D.$: $3.8{\pm}1.6cm^2$). This result shows that results correlate well between the BL and the length and cross section of swimbladder. The swimbladder angle ranged in $7{\sim}12^{\circ}$ and the maximum TS values ranged in $-16{\sim}-5^{\circ}$ at tilt angle. The averaged TS-to-BL relationship were $TS_{38kHz}=20{\log}_{10}BL-65.33$ ($R^2=0.66$), $TS_{70kHz}=20{\log}_{10}BL-65.90$ ($R^2=0.67$), and $TS_{120kHz}=20{\log}_{10}BL-66.65$ ($R^2=0.65$). These results can be used fundamental data in order to estimate distribution and biomass of jack mackerel by using hydro-acoustic method.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2011.06a
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• pp.235-235
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• 2011

Lau basin of south Pacific, as an active back arc basin, is promising area bearing seafloor massive hydrothermal deposit that is located in a subduction zone between the Pacific ocean plate and Indo-Australian continental plate. Korea Ocean Research and Development Institute tracked from 2004 to 2006 the hydrothermal activity to the extension of the northeast Lau Basin, targeting seamount. hydrothermal activity by tracking was found hydrothermal evidences. In this study, Marine seismic survey was carried out in the Lau basin seamount of the possibility of hydrothermal deposit. In particular, Marine magnetic survey and seismic survey was carried out at the same time in TA-12 seamount and noise characteristics were found in the seamount. the main process of data processing is Bandpass filter, FK filter, Deconvolution for noise attenuation such backscatter and multiple reflections. the migration is performed to compensate for reflection points followed by seamount of a slope. In this study, bedrock and upper strata could be identified and in the Future, the comparative method with Multi Beam Echo Sounder(MBES) are likely to derive the correct velocity model, the marine magnetic survey results should be considered.