• 제목/요약/키워드: Broadband acoustic scattering

검색결과 9건 처리시간 0.114초

고등어(Scomber japonicus), 불볼락(Sebastes thompsoni) 및 쥐노래미(Hexagrammos otakii)에 의한 광대역 음향산란신호의 시간-주파수 분석 (Time-Frequency Analysis of Broadband Acoustic Scattering from Chub Mackerel Scomber japonicus, Goldeye Rockfish Sebastes thompsoni, and Fat Greenling Hexagrammos otakii)

  • 이대재
    • 한국수산과학회지
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    • 제48권2호
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    • pp.221-232
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    • 2015
  • Broadband echoes measured in live chub mackerel Scomber japonicus, goldeye rockfish Sebastes thompsoni, and fat greenling Hexagrammos otakii with different morphologies and internal characteristics were analyzed in time and frequency domains to understand the species-specific echo feature characteristics for classifying fish species. The mean echo image for each time-frequency representation dataset obtained as a function of orientation angle was extracted to mitigate the effect of fish orientation on acoustic scattering. The joint time-frequency content of the broadband echo signals was obtained using the smoothed pseudo-Wigner-Ville distribution (SPWVD). The SPWVDs were analyzed for each echo signature of the three fish species. The results show that the time-frequency analysis provided species-specific echo structure patterns and metrics of the broadband acoustic signals to facilitate fish species classification.

펄스압축기법을 이용한 활어 개체어에 대한 광대역 음향산란신호의 분석 및 식별 (Analysis and Classification of Broadband Acoustic Echoes from Individual Live Fish using the Pulse Compression Technique)

  • 이대재;강희영;곽민선
    • 한국수산과학회지
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    • 제48권2호
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    • pp.207-220
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    • 2015
  • This study identified the species-specific, frequency-dependent characteristics of broadband acoustic scattering that facilitate classifying fish species using the pulse compression (PC) technique. Controlled acoustic scattering laboratory experiments were conducted with nine commercially important fish species using linear chirp signals (95-220 kHz) over an orientation angle range of ${\pm}45^{\circ}$ in the dorsal plane at approximately $1^{\circ}$ increments. The results suggest that the angular-dependent characteristics of the broadband echoes and the frequency-dependent variability in target strength (TS) were useful for inferring the fish species of interest. The scattering patterns in the compressed pulse output were extremely complex due to morphological differences among fish species, but the x-ray images strongly suggested that spatial separation correlated well with scattering for the head, skeleton, bone, otoliths, and swim bladder within each specimen.

어류 부레의 형태학적 차이에 따른 음향산란강도의 자세 및 주파수 의존성의 변화 (Changes in the Orientation and Frequency Dependence of Target Strength due to Morphological Differences in the Fish Swim Bladder)

  • 이대재
    • 한국수산과학회지
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    • 제48권2호
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    • pp.233-243
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    • 2015
  • Controlled broadband acoustic scattering laboratory experiments were conducted using a linear chirp signal (95-220 kHz), and x-ray images of live and model fish with an artificial swim bladder were analyzed to investigate the changes in orientation and frequency dependence of target strength (TS) due to morphological differences in fish swim bladders. The broadband echoes from live and model fish were measured over an orientation angle range of ${\pm}45^{\circ}$ in the dorsal plane and in approximately $1^{\circ}$ increments. The location of nulls in the simulated echo response of the SINC [sinc function] model was overlaid on the TS map, showing the orientation and frequency dependence of fish TS, and they matched very well. It was possible to infer the equivalent fish scattering size (or swim bladder) using the null spacing in the experimentally obtained broadband TS map. Good agreement was observed for inferring the equivalent scattering size between the SINC model and the broadband echoes measured for the three fish species (black scraper Thamnaconus modestus; goldeye rockfish Sebastes thompsoni; and whitesaddled reef fish Chromis notatus). Some results of this inference are discussed.

분수차 푸리에 변환을 이용한 스펙트럼상에서 중첩된 학공치(Hypohamphus sajori)의 광대역 음향산란신호의 분리 (Separation of Spectrally Overlapped Broadband Acoustic Scattering Signals from Japanese Needlefish Hypohamphus sajori Using the Fractional Fourier Transform)

  • 이대재
    • 한국수산과학회지
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    • 제55권2호
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    • pp.195-206
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    • 2022
  • The separation of spectrally overlapped broadband echo signals from free-swimming Japanese needlefish Hypohamphus sajori using the fractional Fourier transform (FrFT) was investigated. The broadband echo signals were measured over frequency ranges of 40-80 and 110-220 kHz. The overlapped echo signals were separated after eliminating noise signals in the smoothed pseudo-Wigner-Ville distribution domain. The echo signal from a 40 mm WC sphere suspended just below a chirp transducer was used to calibrate the broadband of the chirp echo sounder and estimate the frequency dependence of target strength for the separated echo signals. The experimental results show that the proposed FrFT method can analyze the time-frequency image of broadband echo signals from free-swimming individual fish effectively and can be used as a quantitative tool for extracting the acoustic features used for fish species identification.

살오징어(Todarodes pacificus)와 갑오징어(Sepia esculenta)에 대한 광대역 음향산란특성의 비교 (Comparison of Broadband Acoustic Scattering Characteristics Between Japanese Flying Squid Todarodes pacificus and Golden Cuttlefish Sepia esculenta)

  • 이대재
    • 한국수산과학회지
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    • 제52권6호
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    • pp.709-718
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    • 2019
  • Cephalopods, such as the Japanese flying squid Todarodes pacificus and golden cuttlefish Sepia esculenta, are an important food source for all toothed whales, particularly bottlenose dolphins in costal and offshore waters around the Korean Peninsula. A controlled laboratory experiment was conducted to investigate the broadband acoustic backscattering from live individuals of these two cephalopod species using linear chirp signals (100-200 kHz). The backscattered echo signal was measured at about 1° intervals from -45° (head down) to +45° (head up) in the dorsal plane. The species-specific, frequency-dependent scattering characteristics were investigated by comparing the relationship between the wavelength-normalized backscattering cross-section (σ/λ2) and the wavelength-normalized fish length L/λ for each species. The estimated σ/λ2 value for Japanese flying squid was 9.51 at an L/λ range of 12.79-30.27 (mean, 21.26). This was approximately 7% of the σ/λ2 value (136.1) for golden cuttlefish at an L/λ range of 9.07-25.49 (mean, 15.77).

볼락의 형태학적 특징과 음향반사강도 특성 (Morphological Properties and Target Strength Characteristics for dark banded rockfish (Sebastes inermis))

  • 황보규
    • 수산해양기술연구
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    • 제51권1호
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    • pp.120-127
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    • 2015
  • Morphological properties of dark banded rockfish (Sebastes inermis) were analysed to investigate its acoustic scattering characteristics. Total of 18 live samples was prepared for X-ray photos and collected morphological coordinates of their body and swim bladder shapes. Kirchhoff-ray mode model was used to calculate acoustic scattering pattern for broad-band frequency range. Inclination of swim bladder ranged from 17 to 30 and the averaged value was about $25.2^{\circ}$ (S.D.(standard deviation)=3.15). There were no any tendency of increase or decrease in volume and area ratio of swim bladder to fish body and ranged from 2.2 % to 4.43 % and 14.85 % to 21.31 %, respectively. The averaged value of volume and area ratio was 3.13 % (S.D.=0.52) and 17.6 % (S.D.=1.5). $b_{20}$ values were -69.01 for 38 kHz, -69.83 for 70 kHz, -70.17 for 120 kHz and -70.93 for 200 kHz, recpectively. Broadband acoustic patterns of dark banded rockfish for 20 ~ 200 kHz were similar among samples and they reflected size and morphological properties of fish species.

어군에 의한 광대역 음향산란신호의 시간-주파수 분석을 위한 chirp 데이터 수록 및 처리 시스템의 성능특성 (Performance Characteristics of a Chirp Data Acquisition and Processing System for the Time-frequency Analysis of Broadband Acoustic Scattering Signals from Fish Schools)

  • 이대재
    • 한국수산과학회지
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    • 제51권2호
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    • pp.178-186
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    • 2018
  • A chirp-echo data acquisition and processing system was developed for use as a simplified, PC-based chirp echo-sounder with some data processing software modules. The design of the software and hardware system was implemented via a field-programmable gate array (FPGA). Digital signal processing algorithms for driving a single-channel chirp transmitter and dual-channel receivers with independent TVG (time varied gain) amplifier modules were incorporated into the FPGA for better real-time performance. The chirp-echo data acquisition and processing system consisted of a notebook PC, an FPGA board, and chirp sonar transmitter and receiver modules, which were constructed using three chirp transducers operating over a frequency range of 35-210 kHz. The functionality of this PC-based chirp echo-sounder was tested in various field experiments. The results of these experiments showed that the developed PC-based chirp echo-sounder could be used in the acquisition, processing and analysis of broadband acoustic echoes related to fish species identification.

확률 신경망에 의한 해저 저질의 식별 (Classifying Seafloor Sediments Using a Probabilistic Neural Network)

  • 이대재
    • 한국수산과학회지
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    • 제51권3호
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    • pp.321-327
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    • 2018
  • To classify seafloor sediments using a probabilistic neural network (PNN), the frequency-dependent characteristics of broadband acoustic scattering, which make it possible to qualitatively categorize seabed type, were collected from three different geographical areas in Korea. The echo data samples from three types of seafloor sediment were measured using a chirp sonar system operating over a frequency range of 20-220 kHz. The spectrum amplitudes for frequency responses of 35-75 kHz were fed into the PNN as input feature parameters. The PNN algorithm could successfully identify three seabed types: mud, mud/shell and concrete sediments. The percentage probabilities of the three seabed types being correctly classified were 86% for mud, 66% for mud/shell and 72% for concrete sediment.

부레를 갖는 6개 어종의 광대역 음향산란특성에 대한 부레 가스 제거의 효과 (The Effect of Removing Swimbladder Gas on the Broadband Acoustic Backscattering Characteristics of Six Species of Swimbladdered Fish)

  • 이대재
    • 한국수산과학회지
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    • 제53권2호
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    • pp.218-230
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    • 2020
  • The single anatomical attribute that has the greatest influence on acoustic scattering from fish is the presence or absence of a swimbladder. This study examined the effect of removing the gas from the swimbladder on the broadband backscattering characteristics of six species of swimbladdered fish: striped beakperch Oplegnathus fasciatus, black scraper Thamnaconus modestus, dark-banded rockfish Sebastes inermis, goldeye rockfish Sebastes thompsoni, black rockfish Sebastes schlegeli and panther puffer Takifugu pardalis. Before and after removing the gas from the swimbladder, the species-specific, frequency-dependent backscattered echo signals from anaesthetized individuals of each fish species were measured at approximately 1° intervals spanning a 90° aspect angle range from -45° (head down) to +45° (head up) using a broadband echo sounder operating at 100-200 kHz. The relationship between the wavelength-normalized backscattering cross section (σ/λ2) and fish length (L/λ) was calculated for each species. The average σ/λ2 value for the six fish species at a L/λ range of 19.79-25.85, with a mean of 22.89, was reduced by approximately 52.3% when the gas was removed.