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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of the Acoustical Society of Korea
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Journal DOI :
The Acoustical Society of Korea
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Volume & Issues
Volume 34, Issue 6 - Nov 2015
Volume 34, Issue 5 - Sep 2015
Volume 34, Issue 4 - Jul 2015
Volume 34, Issue 3 - May 2015
Volume 34, Issue 2 - Mar 2015
Volume 34, Issue 1 - Jan 2015
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Overview of the KIOST-HYU Joint Experiment for Acoustic Propagation in Shallow Water Geological Environment
Cho, Sungho ; Kang, Donhyug ; Lee, Cheol-Ku ; Jung, Seom-Kyu ; Choi, Jee Woong ; Oh, Suntaek ;
The Journal of the Acoustical Society of Korea, volume 34, issue 6, 2015, Pages 411~422
DOI : 10.7776/ASK.2015.34.6.411
This paper presents an overview of the geological environment investigation and underwater acoustic measurements for the purpose of "Study on the Relationship between the Geological Environment and Acoustic Propagation in Shallow Water", which are jointly carried out by KIOST (Korea Institute of Ocean Science & Technology) and Hanyang University in the western shallow water off the Taean peninsula in the Yellow Sea in April-May 2013. The experimental site was made up of various sediment types and bedforms due to the strong tidal currents and coastal geomorphological characteristics. The geological characteristics of the study area were intensively investigated using multi-beam echo sounder, sub-bottom profiler, sparker system and grab sampler. Acoustic measurements with a wide range of research topics in a frequency range of 20~16,000 Hz: 1) low frequency sound propagation, 2) mid-frequency bottom loss, 3) spatial coherence analysis of ambient noise, and 4) mid- frequency bottom backscattering were performed using low- and mid-frequency sound sources and vertical line array. This paper summarizes the topics that motivated the experiment, methodologies of the acoustic measurements, and acoustic data analysis based on the measured geological characteristics, and describes summary results of the geological, meteorological, and oceanographic conditions found during the experiments.
Measurements of Mid-frequency Bottom Loss in Shallow Water of the Yellow Sea
Yoon, Young Geul ; Lee, Changil ; Choi, Jee Woong ; Cho, Sungho ; Oh, Suntaek ; Jung, Seom-Kyu ;
The Journal of the Acoustical Society of Korea, volume 34, issue 6, 2015, Pages 423~431
DOI : 10.7776/ASK.2015.34.6.423
KIOST-HYU joint acoustics experiment was performed on the western shallow water off the Taean peninsula in the Yellow Sea in May 2013. In this paper, mid-frequency (6~16 kHz) bottom loss data measured in a grazing angle range of
are presented and compared to the predictions obtained using a Rayleigh reflection model. The sediment structure of the experimental site was characterized by multi-layered sediment and the components of the surficial sediment consisted of various types of particles with a mean grain size of
. The model predictions obtained using the mean grain size were not in agreement with the measured bottom loss, and those obtained using the grain size of
, which was estimated by an inversion process, showed a best fit to the measurements. It would be because the standard deviation of the gain-size distribution of surficial sediment is
, which is much larger than those of other areas around the experimental site. Finally, the model predictions obtained using the geoacoustic parameters estimated from the inversion process for the surficial sediment layer and those corresponding to the mean grain size of
for lower layer are reasonably agreement with the measured bottom loss data.
Spatial Coherence Analysis of Underwater Ambient Noise Measured at the Yellow Sea
Kwon, Hyuckjong ; Kim, Junghun ; Choi, Jee Woong ; Kang, Donhyug ; Cho, Sungho ; Jung, Seom-Kyu ; Park, Kyeongju ;
The Journal of the Acoustical Society of Korea, volume 34, issue 6, 2015, Pages 432~443
DOI : 10.7776/ASK.2015.34.6.432
Coherence describing the similarity between physical quantities of two signals is a very useful tool to investigate the temporal and spatial characteristics of signals propagating in underwater acoustic waveguide. Ambient noise measurements were made by the vertical received array consisting of three hydrophones as part of the KIOST-HYU joint acoustics experiment, and the coherence for the underwater ambient noise was analyzed. In this paper, the coherence results in cases that the generator in the research vessel was off and turned on are presented. The coherence estimated in the case of the generator operation mode are compared to the predictions obtained using the theoretical model with the directional density function dominated by vertical components propagating downward from the ship. In the case of the generator switch-off, the results are compared to the model predictions with directional density function including the effects of sea surface noise and long-distance shipping noise.
Measurements of Monostatic Bottom Backscattering Strengths in Shallow Water of the Yellow Sea
Son, Wuju ; Son, Su-Uk ; Choi, Jee Woong ; Cho, Sungho ; Jung, Seom-Kyu ;
The Journal of the Acoustical Society of Korea, volume 34, issue 6, 2015, Pages 444~454
DOI : 10.7776/ASK.2015.34.6.444
Measurements of bottom backscattering strengths in a frequency range of 6-14 kHz were made on the shallow water off the southern Gyeonggi Bay in Yellow Sea in May 2013, as part of the KIOST-HYU joint acoustics experiment. Geological surveys for the experimental area were performed using multi-beam echo sounder, sparker system, and grab sampling to investigate the bottom topography, sub-bottom profile and composition of surficial sediment, respectively. In this paper, the backscattering strengths as a function of grazing angle (in range of
) were estimated and compared to the predictions obtained by Lambert`s law and APL-UW scattering model. Finally, the effects of geoacoustic parameters corresponding to the experimental area on the backscattering strengths are discussed.
Effects of Warm Eddy on Long-range Sound Propagation in the East Sea
Kim, Won-Ki ; Cho, Chang-bong ; Park, Joung-Soo ; Hahan, Jooyoung ; Na, Youngnam ;
The Journal of the Acoustical Society of Korea, volume 34, issue 6, 2015, Pages 455~462
DOI : 10.7776/ASK.2015.34.6.455
It is well known that warm eddy is frequently developed through the year in the East Sea. The warm eddy may affect sound propagation due to changes of sound velocity structures in the sea water. To verify the effects of the warm eddy for long-range sound propagation, transmission loss and performance surface, which were used mean direct signal excess range generated by sound propagation modeling using re-analyzed climatology data on March 23th in 2007 were analysed. From these analyses, we found that characteristics of sound propagation in the sea water are changed by the warm eddy, and boundaries of the warm eddy act as a barrier for long-range sound propagation. Furthermore, these disadvantages of the eddy related to sound propagation were increased when the sea bottom depth is shallow.
Performance Evaluation of an Underwater Propagation Delay-Aware Medium Access Control Protocol
Hwang, Ho Young ; Kim, Woo-Sik ; Lee, Sang-Kug ; Cho, Ho-Shin ;
The Journal of the Acoustical Society of Korea, volume 34, issue 6, 2015, Pages 463~469
DOI : 10.7776/ASK.2015.34.6.463
In this paper, we propose an underwater propagation delay-aware medium access control protocol and evaluate the performance of the proposed protocol. In the proposed propagation delay-aware medium access control protocol, a sink node can restore the received RTS frames that are not piled up in a slot time. We analyze and compare the performance of the proposed underwater propagation delay-aware medium access control protocol with that of the conventional medium access control protocol in various environments.
Validity of Two-layered Ocean Bottom Model for Ray Model
Lee, Keunhwa ; Seong, Woojae ;
The Journal of the Acoustical Society of Korea, volume 34, issue 6, 2015, Pages 470~478
DOI : 10.7776/ASK.2015.34.6.470
A heuristic method treating a layered ocean bottom in a ray modeling is to use the plane wave reflection coefficient for multiple-layered structure, named an one-layer assumption in this paper. We examine the validity of one-layer assumption in the case of two-layered ocean bottom, and obtain a simple inequality condition depending on the sound speed ratio, the ratio of layer thickness to source-receiver range, and the grazing angle of first reflected ray. From this inequality condition, it is shown that an one-layer assumption can be applicable to ray propagation problems at mid frequencies. Finally, numerical experiments are performed in the ocean environment similar to the East Sea in Korea. Incoherent transmission loss is calculated by the geometrical beam model with the plane wave reflection coefficient for multiple-layered ocean bottom and compared with the result of SNUPE 2.0, which is a parabolic equation package developed in Seoul National University.
Analysis on Noise Correlation of Triplet Line Array Sensors in the East Sea
Ryu, Youngwoo ; Jeong, Euicheol ; Chun, Seung-yong ;
The Journal of the Acoustical Society of Korea, volume 34, issue 6, 2015, Pages 479~486
DOI : 10.7776/ASK.2015.34.6.479
A triplet line array has a capability for solving left/right ambiguity problem and high directivity of line array. For this, high computational powers and correlation between nearby sensors must be considered. Hardware powers are dramatically increased, so various adaptive beamforming techniques and signal processing techniques can be adopted for large triplet line array. To investigate the optimum signal processing method and improve the target detection capability, we need to analyze the noise correlation among the triplet line array sensors in real environment. In this paper we analyze the experimental data in the East Sea, investigate noise correlation between three hydrophones in triplet sensors, among the triplet sensors and time varying properties. Based on the acquired results, it is possible to verify some information for beamforming and signal processing methods with considering the properties of the triplet line array.
A Study on the Underwater Target Detection Using the Waveform Inversion Technique
Bae, Ho Seuk ; Kim, Won-Ki ; Kim, Woo Shik ; Choi, Sang Moon ;
The Journal of the Acoustical Society of Korea, volume 34, issue 6, 2015, Pages 487~492
DOI : 10.7776/ASK.2015.34.6.487
A short-range underwater target detection and identification techniques using mid- and high-frequency bands have been highly developed. However, nowadays the long-range detection using the low-frequency band is requested and one of the most challengeable issues. The waveform inversion technique is widely used and the hottest technology in both academia and industry of the seismic exploration. It is based on the numerical analysis tool, and could construct more than a few kilometers of the subsurface structures and model-parameters such as P-wave velocity using a low-frequency band. By applying this technique to the underwater acoustic circumstance, firstly application of underwater target detection is verified. Furthermore, subsurface structures and it`s parameters of the war-field are well reconstructed. We can confirm that this technique greatly reduces the false-alarm rate for the underwater targets because it could accurately reproduce both the shape and the model-parameters at the same time.
Determination of Plane-wave Reflection Coefficient in Underwater Acoustic Pulse Tube Using Two-dimensional Fourier Filtering
Kim, Wan-Gu ; Kang, Hwi Suk ; Yoon, Suk Wang ;
The Journal of the Acoustical Society of Korea, volume 34, issue 6, 2015, Pages 493~498
DOI : 10.7776/ASK.2015.34.6.493
Complex acoustic signals can be formed in a water-filled acoustic pulse tube under some exciting conditions. It makes difficult to measure plane-wave reflection coefficient with the pulse tube for low frequency bands. In this study, using COMSOL Multiphysics we show that the tube wall excitation generates complex acoustic field of nonplanar mode as well as planar one. From such field incident or reflected planar mode can be decomposed respectively with a modal decomposition method, two-dimensional Fourier filtering. It makes possible to more accurately determine the plane-wave reflection coefficient of acoustic specimen with time gating.