Sediment sound speeds from a monostatic (multibeam) sonar

2020 ◽  
Vol 148 (4) ◽  
pp. 2443-2443
Author(s):  
Charles W. Holland ◽  
Samuel Pinson
Keyword(s):  
Multibeam Sonar ◽  
Sound Speeds

ANALYSIS OF SOUND SPEED IN LONGITUDINAL DIRECTION AT REFERENCE MOISTURE CONTENT (w = 12 %) IN SAWMILL ASSORTMENTS (FAGUS SYLVATICA, L.)

Akustika ◽  
2020 ◽  
pp. 45-50
Author(s):  
Alena Rohanová
Keyword(s):  
Moisture Content ◽  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
Sound Speed ◽  
Longitudinal Direction ◽  
Structural Timber ◽  
Sound Speeds ◽  
Dynamic Modulus Of Elasticity ◽  
Round Timber

This paper explores the analysis of sound speeds in the longitudinal direction and their reduction to the reference moisture content w = 12 %. The sound speed cw was determined with Sylvatest Duo device. Moisture content of beech sawmill assortments (round timber: N = 16, logs: N = 2 × 16, structural boards: N = 54) in the range of 12 – 72 % was measured. For the analysis purposes, the sound speed was converted to reference conditions (c12, uref = 12%). A second-degree polynomial (parabola) with a regression equation of the form: c// = 5649 - 27,371 × w + 0.0735 × w2 was used to convert cw to c12, and correction of measured and calculated values was used as well. The sound speeds c12 in sawmill assortments (c12,round, c12,log, c12,board) were evaluated by linear dependences. Dependence was not confirmed for c12,round and c12,board1 (r = 0.168), in contrast for c12,round and c12,log2 the dependence is statistically very significant (r = 0.634). The results of testing showed that the most suitable procedure for predicting quality of structural timber is the first step round timber – log2, the second step: log2 - board2. More exact results of the construction boards were obtained from log2 than from log1. The sound speed is used in the calculation of dynamic modulus of elasticity (Edyn). EN 408 mentions the possibility of using dynamic modulus of elasticity as an alternative method in predicting the quality of structural timber.

Development of Mid-Frequency Multibeam Sonar for Fisheries Applications

2006 ◽  
Author(s):  
John K. Horne ◽  
Christopher D. Jones ◽  
Mike A. Wolfson
Keyword(s):  
Multibeam Sonar

scholarly journals Smart Ocean: A New Fast Deconvolved Beamforming Algorithm for Multibeam Sonar

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 4013 ◽  
Author(s):  
Jie Huang ◽  
Tian Zhou ◽  
Weidong Du ◽  
Jiajun Shen ◽  
Wanyuan Zhang
Keyword(s):  
High Frequency ◽  
Real Data ◽  
Side Lobe ◽  
Tunnel Effect ◽  
Computation Complexity ◽  
Acoustic Image ◽  
Multibeam Sonar ◽  
Sonar System ◽  
Topographic Survey ◽  
Beamforming Algorithm

A new fast deconvolved beamforming algorithm is proposed in this paper, and it can greatly reduce the computation complexity of the original Richardson–Lucy (R–L algorithm) deconvolution algorithm by utilizing the convolution theorem and the fast Fourier transform technique. This algorithm makes it possible for real-time high-resolution beamforming in a multibeam sonar system. This paper applies the new fast deconvolved beamforming algorithm to a high-frequency multibeam sonar system to obtain a high bearing resolution and low side lobe. In the sounding mode, it restrains the tunnel effect and makes the topographic survey more accurate. In the 2D acoustic image mode, it can obtain clear images, more details, and can better distinguish two close targets. Detailed implementation methods of the fast deconvolved beamforming are given, its computational complexity is analyzed, and its performance is evaluated with simulated and real data.

scholarly journals Observations of Shallow Methane Bubble Emissions From Cascadia Margin

2021 ◽  
Vol 9 ◽  
Author(s):  
Anna P. M. Michel ◽  
Victoria L. Preston ◽  
Kristen E. Fauria ◽  
David P. Nicholson
Keyword(s):  
Water Column ◽  
Water Depth ◽  
Dissolved Methane ◽  
Multibeam Sonar ◽  
Surface Ocean ◽  
Transient Nature ◽  
Technological Approach ◽  
Open Questions ◽  
Cascadia Margin ◽  
Methane Bubble

Open questions exist about whether methane emitted from active seafloor seeps reaches the surface ocean to be subsequently ventilated to the atmosphere. Water depth variability, coupled with the transient nature of methane bubble plumes, adds complexity to examining these questions. Little data exist which trace methane transport from release at a seep into the water column. Here, we demonstrate a coupled technological approach for examining methane transport, combining multibeam sonar, a field-portable laser-based spectrometer, and the ChemYak, a robotic surface kayak, at two shallow (<75 m depth) seep sites on the Cascadia Margin. We demonstrate the presence of elevated methane (above the methane equilibration concentration with the atmosphere) throughout the water column. We observe areas of elevated dissolved methane at the surface, suggesting that at these shallow seep sites, methane is reaching the air-sea interface and is being emitted to the atmosphere.

scholarly journals Estimating the frequency dependent behavior of marine sediment sound speeds using low frequency aircraft sound

2008 ◽  
Vol 123 (5) ◽  
pp. 3349-3349
Author(s):  
Alireza Amiri‐Simkooei ◽  
Mirjam Snellen ◽  
Dick G. Simons ◽  
Michael Buckingham
Keyword(s):  
Marine Sediment ◽  
Low Frequency ◽  
Frequency Dependent ◽  
Sound Speeds ◽  
Dependent Behavior

scholarly journals Comparison of model types for prediction of seafloor trawlability in the Gulf of Alaska by using multibeam sonar data

2021 ◽  
Vol 119 (2-3) ◽  
pp. 184-196
Author(s):  
Sarah C. Stienessen ◽  
Christopher N. Rooper ◽  
Thomas C. Webe ◽  
Darin T. Jones ◽  
Jodi L. Pirtle ◽  
...  
Keyword(s):  
Gulf Of Alaska ◽  
Multibeam Sonar

THEORY OF THIRD SOUND AND STABILITY OF THIN 3He–4He SUPERFLUID FILMS

2007 ◽  
Vol 21 (13n14) ◽  
pp. 2091-2102
Author(s):  
M. D. MILLER ◽  
E. KROTSCHECK
Keyword(s):  
Numerical Density ◽  
Boson Systems ◽  
Hydrodynamic Description ◽  
Third Sound ◽  
Sound Speeds ◽  
The Third ◽  
Chemical Potentials ◽  
Hypernetted Chain ◽  
Superfluid Films ◽  
Sound Spectrum

In this paper, we summarize the results of recent studies of third sound in thin, superfluid 3 He -4 He mixture films and the relation of the third sound spectrum to the question of the films' thermodynamic stability. We have considered films on several representative substrates: Nuclepore, glass, Li and Na . Our approach utilizes the variational, hypernetted chain/Euler-Lagrange (HNC–EL) theory as applied to inhomogeneous boson systems to calculate chemical potentials for both the 4 He superfluid film and the physisorbed 3 He . Numerical density derivatives of the chemical potentials lead to the sought-after third sound speeds. On all substrates, the third sound speeds show a series of oscillations as a function of film coverage that is driven by the layered structure of the 4 He film. We find that the effect on the third sound response of adding a small amount of 3 He to the 4 He film can depend sensitively on the particular 4 He film coverage. The third sound speed can either increase or decrease. In fact, in some regimes, the added 3 He destabilizes the film and can drive "layering transitions" leading to quite complicated geometric structures of the film in which the outermost layer consists of phase–separated regimes of 3 He and 4 He . Finally, we examine the range of applicability of the usual film–averaged hydrodynamic description. We find that at least up to film thicknesses of six liquid layers, there is no regime in which this hydrodynamic description is applicable.

General relationships among sound speeds

1974 ◽  
Vol 8 (2) ◽  
pp. 121-129 ◽  
Author(s):  
T.J. Shankland ◽  
D.H. Chung
Keyword(s):  
Sound Speeds
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