• Title/Summary/Keyword: 음향상

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Performance Comparison of Acoustic Equalizers using Adaptive Algorithms in Shallow Water Condition (천해환경에서 적응 알고리즘을 이용한 음향 등화기의 성능 비교)

  • Chuai, Ming;Park, Kyu-Chil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.22 no.2
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    • pp.253-260
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    • 2018
  • The acoustic communication channel in shallow underwater is typically shown as time-varying multipath fading channel characteristics. The received signal through channel transmission cause inter-symbol interference (ISI) owing to multiple components of different time delay and amplitude. To compensate for this, several techniques have been used, and one of them is acoustic equalizer. In this study, we used four equalizers - feed forward equalizer (FFE), decision directed equalizer (DDE), decision feedback equalizer (DFE) and combination DDE with DFE to compensate ISI. And we applied two adaptive algorithms to adjust coefficient of equalizers - normalized least mean square algorithm and recursive least square algorithm. As result, we found that it has a significant performance improvement over 6 dB on SNR in nonlinear equalizer. By combination of DFE and DDE has almost best performance in any case.

Dead Zone Correction for Abundance Estimation of Demersal Fish by Acoustic Method (저서어자원량의 음향추정에 있어서 해저 데드존의 보정에 관한 연구)

  • 황두진
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.36 no.3
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    • pp.202-209
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    • 2000
  • In order to estimate demersal fishes using acoustic echo sounders and echo integrators, we consider several problems that are accurate bottom detection, optimum bottom offset and dead zone. The dead zone where no fish detection are summed distance resolution by the half pulse length of transmitted pulse and beam angle above the seabed. This paper has considered the dead-zone correction method to be technically correct for survey of demersal fishes. A comparison between near-bottom SV profiles acquired in Funka Bay, Hokkaido, of Japan, the East China Sea and the Yellow Sea, of Korea, with before and after the bottom correction, shows that the SV obtained with after the bottom correction is 2∼3dB higher than before the bottom correction in Funka Bay, and 17dB higher in East China Sea, too.

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The role of Under-balcony Speaker in the Multimedia Environmental (멀티미디어 환경에서 언더발코니 스피커의 역할)

  • Song, Deog-Geun;Park, Eun-Jin;Lee, Seon-Hee
    • Journal of Satellite, Information and Communications
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    • v.10 no.2
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    • pp.86-89
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    • 2015
  • Formula acoustic characteristics of the room with a double layer, are compared through simulation and actual measurement. The rear area of the under- balcony speakers will cause a delay difference between the main speaker. In the mid / bass parts do not generate sufficient pressure is lowered and comb-Filtering phenomenon occurs significantly. The lower right area of the under- balcony speakers and speaker distance is the sound pressure of the under- balcony speakers to around 2 ~ 3m bigger than the main speakers and the sound image matches the pulpit is broken. Also, under area is more than 5 ~ 6m from the balcony outside speakers and causes differ by more than 10dB lower than the under- balcony speakers depending on the local laws of Translator wins Well, the main speaker at mid / high frequency sounds do not enter the sound pressure variations will drop by a significant. Appropriate arrangement and the output of the speaker according to the position under the balcony, and output of the main speakers are requested to minimize this problem sound. The proper sound design direction for the under- balcony speakers must be presented in order to improve the lower balcony area more pleasant acoustic environment.

수질모의에 필요한 수체자료의 취득방안

  • Lee, Yo-Sang;Kang, Sung Dai
    • Proceedings of the Korea Water Resources Association Conference
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    • 2004.05b
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    • pp.1434-1438
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    • 2004
  • 저수지 수질모형의 기초자료로서의 수체의 수리학적 인자는 물리적인 자료이므로 많은 실측 자료를 필요로 한다. 이러한 자료의 취득을 위하여 수체의 수심을 측정하고, 대상구역의 수계특성을 잘 반영할 수 있도록 수체를 분할하여 각 구간별 수체 중심, 특성길이, 연직 및 수평 단면적, 수표면적, 수체적, 수로경사 등을 구하여 사용한다. 이러한 자료의 취득은 여러 가지 어려움으로 인하여 조사지점이 조밀하지 못하거나 계간방법이 개발되지 못하는 등의 이유로 인하여 실제값과 상당한 차이를 나타내기도 하므로 이를 개선할 수 있는 방법을 제시하고자 한다. 최근에 개발된 다중 음향탐사기 (MBES)는 초음파를 발사하여 하상에서 반사한 파의 시간을 측정하고 거리로 환산하여 수심을 측정하는 것으로 여러 지점의 수심을 동시에 스캔할 수 있다는 장점이 있다. 또한 MBES는 수신기의 지향각이 존재하므로 파의 반사지점을 정확하게 파악할 수 있다. 단일 음향측심기는 측선을 따라 수심을 측정하므로 조사간격이 넓어 정확한 수로정보를 얻기에는 미흡한 점이 있으나 MBES는 수체 전체를 $1\times1m$$4\~5$ 번의 측정하고, 변화가 심한 호저면에서도 수심오차 $5\~8 cm$의 고분해능을 갖는다. 이를 이용하면 하상의 수심에 내한 3차원의 연속분포를 생성하고, 하상의 지형적인 특징을 조사${\cdot}$ 분석할 수 있으며 하상의 성상과정에 관한 기초자료로도 활용한 수 있다. 수체정보를 산정할 때 단일 음향측심법은 간접적으로 자료를 취득하므로 주관적인 견해 및 큰 오차를 내포하고 있으나, MBES는 Hypack Max를 이용하여 구획한 구간에 따른 수표면적과 연직단면적 및 수체적을 자동으로 계산한다. 그리고 측정한 자료의 raw data를 이용하면 각 구간에 대한 무게중심을 구하여 중점으로 사용 가능하고, 종방향의 구축을 산정하여 수로의 깊이 및 중심간 길이를 정확하게 계산할 수 있다.

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Geophysical investigation of methane seeps on the NE Sakhalin continental slope, Sea of Okhotsk (오호츠크해 북동사할린 대륙사면에 나타나는 메탄분출구에 대한 지구물리탐사)

  • Jin, Young-Keun;SSGH-Scientific-Party, SSGH-Scientific-Party
    • 한국지구물리탐사학회:학술대회논문집
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    • 2008.10a
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    • pp.137-140
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    • 2008
  • During CHAOS (2003, 2006) and SSGH projects (2007), acoustic investigation including hydroacoustic (HA), side-scan sonar (SSS) and highresolution sparker seismic (HSS) surveys was carried out on the northeastern Sakhalin slope ($53^{\circ}56'\;N$, $143^{\circ}52'\;E$ to $54^{\circ}40'\;N$, $144^{\circ}32'\;E$). More than 130 methane seeps with high backscatter intensity are identified on SSS mosaic, which are well accompanied with gas flares in the water column on HA profiles and subbottom gas chimneys on HSS profiles. It is likely that that some seeps align along a NW strike parallel to the Lavrentiev Fault.

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Case Study of Ultra High Resolution Shallow Acoustic Profiling - Discrimination of the Marine Contaminated Sediment and Burial Depth Inspection of Submarine Cable (초고해상 천부음향탐사 사례 - 오염퇴적층 구분과 해저케이블 매설 검측)

  • Jung, Baek-Hoon;Lee, Yong-Kuk;Kim, Seong-Ryul;Shin, Dong-Hyeok;Jou, Hyeong-Tae
    • 한국지구물리탐사학회:학술대회논문집
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    • 2008.10a
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    • pp.79-84
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    • 2008
  • Compared to conventional high resolution acoustic profiling, ultra high resolution shallow acoustic profiling is limited in penetration, yet it provides resolution suitable for detailed seabed investigation in the shallow waters. Possible applications include search of buried pipeline, ship wrecks, and other artificial objects through the detailed mapping of thickness and structure of the upper sedimentary layers. In this study, contaminated sediments were discriminated by the correlation of ultra high resolution profiles with geologic data. In addition, the burial depth of submarine cable was measured by the interpretation of acoustic anomalies in the profiles.

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Improved CycleGAN for underwater ship engine audio translation (수중 선박엔진 음향 변환을 위한 향상된 CycleGAN 알고리즘)

  • Ashraf, Hina;Jeong, Yoon-Sang;Lee, Chong Hyun
    • The Journal of the Acoustical Society of Korea
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    • v.39 no.4
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    • pp.292-302
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    • 2020
  • Machine learning algorithms have made immense contributions in various fields including sonar and radar applications. Recently developed Cycle-Consistency Generative Adversarial Network (CycleGAN), a variant of GAN has been successfully used for unpaired image-to-image translation. We present a modified CycleGAN for translation of underwater ship engine sounds with high perceptual quality. The proposed network is composed of an improved generator model trained to translate underwater audio from one vessel type to other, an improved discriminator to identify the data as real or fake and a modified cycle-consistency loss function. The quantitative and qualitative analysis of the proposed CycleGAN are performed on publicly available underwater dataset ShipsEar by evaluating and comparing Mel-cepstral distortion, pitch contour matching, nearest neighbor comparison and mean opinion score with existing algorithms. The analysis results of the proposed network demonstrate the effectiveness of the proposed network.

Transducer Combination for High-Quality Ultrasound Tomography Based on Speed of Sound Imaging (속도 분포 기반 단층촬영을 위한 최적의 트랜스듀서의 조합)

  • Kim, Young Hun;Park, Kwan Kyu
    • Journal of the Korean Society for Nondestructive Testing
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    • v.36 no.1
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    • pp.27-34
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    • 2016
  • The type of ultrasound transducer used influences the quality of a reconstructed ultrasound image. This study analyzed the effect of transducer type on ultrasound computed tomography (UCT) image quality. The UCT was modeled in an ultrasound simulator by using a 5 cm anatomy model and a ring-shape 5 MHz 128 transducer array, which considered attenuation, refraction, and reflection. Speed-of-sound images were reconstructed by the Radon transform as the UCT image modality. Acoustic impedance images were also reconstructed by the delay-and-sum (DAS) method, which considered the speed of sound information. To determine the optimal combination of transducers in observation, point-source, flat, and focused transducers were tested in combination as trasmitters and receivers; UCT images were constructed from each combination. The combination of point-source/flat transducer as transmitting and receiving devices presented the best reconstructed image quality. In UCT implementation, the combination of a flat transducer for transmitting and a point transducer for receiving permitted acceptable image quality.

A Comparison of Bioacoustic Recording and Field Survey as Bird Survey Methods - In Dongbaek-dongsan and 1100-altitude Wetland of Jeju Island - (조류 조사 방법으로써 생물음향 녹음과 현장 조사의 비교 - 제주 동백동산과 1100고지 습지를 대상으로 -)

  • Se-Jun Choi;Kyong-Seok Ki
    • Korean Journal of Environment and Ecology
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    • v.37 no.5
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    • pp.327-336
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    • 2023
  • This study aimed to propose an effective method for surveying wild birds by comparing the results of bioacoustic detection with those obtained through a field survey. The study sites were located at Dongbaek-dongsan and a 1100-altitude wetland in Jeju-do, South Korea. The bioacoustic detection was conducted over the course of 12 months in 2020. For the bioacoustic detection, a Song-meter SM4 device was installed at each study site, recording bird songs in 1-min per hour, .wav, and 44,100 Hz format. The findings of the field survey were taken from the 「Long-term trends of Bird Community at Dongbaekdongsan and 1100-Highland Wetland of Jeju Island, South Korea.」 by Banjade et al. (2019). The results of this study are as follows. First, the avifauna identified using bioacoustic detection comprised 29 families and 46 species in Dongbaek-dongsan, and 16 families and 25 species in the 1100-altitude wetland. Second, based on the song frequency, the dominant species in Dongbaek-dongsan were Hypsipetes amaurotis (Brown-eared Bulbul, 33.62%), Horornis diphone (Japanese Bush Warbler, 12.13%), and Zosterops japonicus (Warbling White-eye, 9.77%). In the 1100-altitude wetland the dominant species were Corvus macrorhynchos (Large-billed Crow, 27.34%), H. diphone (19.43%), and H. amaurotis (16.56%). Third, in the field survey conducted at Dongbaek-dongsan, the number of detected bird species was 39 in 2009, 51 in 2012, 35 in 2015, and 45 in 2018, while the bioacoustic detection identified 46 species. In the field survey conducted in the 1100-altitude wetland, the number of detected bird species was 37 in 2009, 42 in 2012, 34 in 2015, and 38 in 2018, while the bioacoustics detection identified 25 species. Overall, 43.6% of the 78 species detected in the field survey in Dongbaek-dongsan (34 species) were identified using bioacoustic detection, and 38.3% of the 47 species detected in the field survey in the 1100-altitude wetland (18 species) were identified using bioacoustic detection. Fourth, the bioacoustic detection identified 9 families and 12 species of birds in Dongbaek-dongsan, and 3 families and 7 species of birds in the 1100-altitude wetland. No results from field survey were available for these species. The identified birds were predominantly nocturnal, including Otus sunia (Oriental Scops Owl) and Ninox japonica (Northern Boobook), passage migrants, including Larvivora cyane (Siberian Blue Robin), L. sibilans (Rufous-tailed Robin), and winter visitors with a relatively small number of visiting individuals, such as Bombycilla garrulus (Bohemian Waxwing) and Loxia curvirostra (Red Crossbill). Fifth, the birds detected in the field survey but not through bioacoustic detection included 18 families and 48 species in Dongbaek-dongsan and 14 families and 27 species in the 1100-altitude wetland; the most representative families were Ardeidae, Accipitridae, and Muscicapidae. This study is significant as it provides essential data supporting the possibility of an effective survey combining bioacoustic detection with field studies, given the increasing use of bioacoustic devices in ornithological studies in South Korea.

The Design of Broadband Ultrasonic Transducers for Fish Species Identification - Bandwidth Enhancement of a Ultrasonic Transducer Using Double Acoustic Matching Layers- (어종식별을 위한 광대역 초음파 변환기의 설계 ( III ) - 이중음향정합층을 이용한 초음파 변환기의 대역폭 확장 -)

  • 이대재
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.34 no.1
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    • pp.85-95
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    • 1998
  • The broadband ultrasonic transducers have been designed to use in obtaining the broadband echo signals from fish schools in relation to the identification of fish species. The broadening of bandwidth was achieved by attaching double acoustic matching layers on the front face of a Tonpilz transducer consisted of an aluminum head, a piezoelectric ring, a brass tail and to evaluate the performance characteristics, such as the transmitting voltage response(TVR) of transducers. The constructed transducers were tested experimentally and numerically by changing the parameters such as impedances and thicknesses of the head, tail and matching layers, in the water tank. Also, the developed transducer was excited by a chirp signal and the received chirp waveforms were analyzed. According to the measured TVR results, the available 3 dB bandwidth of the transducer with double matching layers of an $Al_O_3/epoxy$ composite of 7 mm thick and a polyurethane window of 18 mm thick was 7.3 kHz with a center frequency of 38.8 kHz, and the maximum and the minimum values of the TVR in this frequency region were 135.7 dB and 132.7 dB re $1\;{\mu}Pa/V$ at 1 m, respectively. Also, the available 3 dB bandwidth of the transducer with double matching layers of an $Al_O_3/epoxy$ composite of 11 mm thick and a polyurethane window of 15 mm thick was 6.2 kHz with a center frequency of 38.6 kHz, and the maximum TVR value in the frequency region was 136.3 dB re $1\;{\mu}Pa/V$ at 1 m. Reasonable agreement between the experimental results and the numerical results for the TVR of the developed transducers was achieved. The frequency dependant characteristics of experimentally observed chirp signals closely matched to the measured TVR results. These results suggest that there is potential for increasing the bandwidth by varying other parameters in the transducer design and the material of the acoustic matching layers.

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