scholarly journals High‐frequency acoustic penetration into seafloor sediments at subcritical grazing angles due to roughness at the water–sediment interface

1995 ◽  
Vol 97 (5) ◽  
pp. 3387-3387
Author(s):  
Eric I. Thorsos
Keyword(s):  
High Frequency ◽  
Acoustic Penetration ◽  
Grazing Angles ◽  
Seafloor Sediments ◽  
Sediment Interface

TWO MODELING APPROACHES FOR REVERBERATION IN A SHALLOW WATER WAVEGUIDE WHERE THE SCATTERING ARISES FROM A SUB-BOTTOM INTERFACE

2009 ◽  
Vol 17 (01) ◽  
pp. 29-43 ◽  
Author(s):  
CHARLES W. HOLLAND ◽  
DALE D. ELLIS
Keyword(s):  
Shallow Water ◽  
Silty Clay ◽  
Sediment Layer ◽  
Angle Distribution ◽  
Vertical Angle ◽  
Fine Grained ◽  
Bottom Interface ◽  
Grazing Angles ◽  
Scattering Kernel ◽  
Sediment Interface

In shallow water environments where the uppermost sediment layer is a fine-grained fabric (e.g. clay or silty-clay), the observed reverberation may be dominated by scattering from the sub-bottom. Here, reverberation predictions from normal mode and energy flux models are compared for the case where the scattering arises from a sub-bottom half-space under a fine-grained sediment layer. It is shown that in such an environment, the position of the angle of intromission, in addition to the angular dependence of the scattering kernel, is a factor controlling the reverberation and its vertical angle distribution. It is also shown that the reverberation from a sub-bottom horizon is typically governed by higher grazing angles than the case where the scattering occurs at the water–sediment interface. There was generally very close agreement between the models as a function of frequency (200–1600 Hz), layer thickness (0–8 m), and range (1–15 km). The model comparisons, showing some differences, illuminate the result of different approximations in the two approaches.

High-frequency subcritical acoustic penetration into a sandy sediment

2002 ◽  
Vol 27 (3) ◽  
pp. 346-361 ◽  
Author(s):  
D.R. Jackson ◽  
K.L. Williams ◽  
E.I. Thorsos ◽  
S.G. Kargl
Keyword(s):  
High Frequency ◽  
Sandy Sediment ◽  
Acoustic Penetration

High‐frequency acoustic penetration of sandy ocean sediments

1991 ◽  
Vol 89 (4B) ◽  
pp. 1908-1908 ◽  
Author(s):  
Nicholas P. Chotiros ◽  
Michael L. Ramaker
Keyword(s):  
High Frequency ◽  
Acoustic Penetration

High‐frequency acoustic penetration of ocean sediments

1994 ◽  
Vol 96 (5) ◽  
pp. 3265-3265
Author(s):  
Nicholas P. Chotiros ◽  
Robert A. Altenburg ◽  
Stephen J. Stanic
Keyword(s):  
High Frequency ◽  
Acoustic Penetration

scholarly journals The second Born approximation and high‐frequency scattering at low grazing angles

1986 ◽  
Vol 79 (S1) ◽  
pp. S68-S68 ◽  
Author(s):  
Stanley A. Chin‐Bing ◽  
Michael F. Werby ◽  
Steve Stanic
Keyword(s):  
Born Approximation ◽  
High Frequency ◽  
Grazing Angles

scholarly journals Insights into the Short-Term Tidal Variability of Multibeam Backscatter from Field Experiments on Different Seafloor Types

Geosciences ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 34 ◽  
Author(s):  
Giacomo Montereale-Gavazzi ◽  
Marc Roche ◽  
Koen Degrendele ◽  
Xavier Lurton ◽  
Nathan Terseleer ◽  
...  
Keyword(s):  
High Frequency ◽  
Field Experiments ◽  
Ground Truth ◽  
Environmental Data ◽  
Absolute Calibration ◽  
Short Term ◽  
Ground Truth Data ◽  
Nearshore Area ◽  
The North ◽  
Sediment Interface

Three experiments were conducted in the Belgian part of the North Sea to investigate short-term variation in seafloor backscatter strength (BS) obtained with multibeam echosounders (MBES). Measurements were acquired on predominantly gravelly (offshore) and sandy and muddy (nearshore) areas. Kongsberg EM3002 and EM2040 dual MBES were used to carry out repeated 300-kHz backscatter measurements over tidal cycles (~13 h). Measurements were analysed in complement to an array of ground-truth variables on sediment and current nature and dynamics. Seafloor and water-column sampling was used, as well as benthic landers equipped with different oceanographic sensors. Both angular response (AR) and mosaicked BS were derived. Results point at the high stability of the seafloor BS in the gravelly area (<0.5 dB variability at 45° incidence) and significant variability in the sandy and muddy areas with envelopes of variability >2 dB and 4 dB at 45° respectively. The high-frequency backscatter sensitivity and short-term variability are interpreted and discussed in the light of the available ground-truth data for the three experiments. The envelopes of variability differed considerably between areas and were driven either by external sources (not related to the seafloor sediment), or by intrinsic seafloor properties (typically for dynamic nearshore areas) or by a combination of both. More specifically, within the gravelly areas with a clear water mass, seafloor BS measurements where unambiguous and related directly to the water-sediment interface. Within the sandy nearshore area, the BS was shown to be strongly affected by roughness polarization processes, particularly due to along- and cross-shore current dynamics, which were responsible for the geometric reorganization of the morpho-sedimentary features. In the muddy nearshore area, the BS fluctuation was jointly driven by high-concentrated mud suspension dynamics, together with surficial substrate changes, as well as by water turbidity, increasing the transmission losses. Altogether, this shows that end-users and surveyors need to consider the complexity of the environment since its dynamics may have severe repercussions on the interpretation of BS maps and change-detection applications. Furthermore, the experimental observations revealed the sensitivity of high-frequency BS values to an array of specific configurations of the natural water-sediment interface which are of interest for monitoring applications elsewhere. This encourages the routine acquisition of different and concurrent environmental data together with MBES survey data. In view of promising advances in MBES absolute calibration allowing more straightforward data comparison, further investigations of the drivers of BS variability and sensitivity are required.

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