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Seabed geoacoustic characterization with a vector sensor arraya)
a)Part of this work was presented at the Third International Conference on Underwater Acoustic Measurements: Technologies and Results, Nafplion, Greece, June 2009.
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Image of FIG. 1.
FIG. 1.

Diagram of the ray trajectory (dashdot line) with ray unitary vectors and projections onto the horizontal and vertical axes.

Image of FIG. 2.
FIG. 2.

Array coordinates and geometry of acoustic plane wave propagation, with azimuth and elevation angles. The vector sensor elements are located in the -axis with the first element at the origin of the cartesian coordinate system.

Image of FIG. 3.
FIG. 3.

DOA estimation simulation results at frequency 7500 Hz with azimuth and elevation angles using the normalized Bartlett beamformer considering: (a) -only response, (b) the of Eq. (26) , (c) the of Eq. (27) , (d) -only (26), and (e) all sensors VSA (27) .

Image of FIG. 4.
FIG. 4.

Simulation scenario based on the typical setup encountered during the Makai experiment with a very large mixed layer, characteristic of Hawaii. The source is bottom moored at 98 m depth and 1830 m range. The VSA is deployed with the deepest element at 79.9 m.

Image of FIG. 5.
FIG. 5.

Seabed parameters estimation simulation results obtained with the normalized Bartlett estimator at frequency 13078 Hz and for for [(a) and (c)] sediment compressional speed where and [(b) and (d)] density where . The simulation results were obtained comparing: the -only Bartlett estimator response (24) for 4 and 16 pressure sensors with VSA Bartlett estimator response (27) (a) and (b) and the Bartlett estimator response considering: individual data components ( , and ), -only Bartlett estimator (VSA ) and all sensors (VSA ) (c) and (d).

Image of FIG. 6.
FIG. 6.

Bathymetry map of the Makai Experiment area with the location of the VSA for the two deployments (September 20th and 25th) as well as the location of the acoustic sources TB2 (fixed) and Lubell916C (track).

Image of FIG. 7.
FIG. 7.

Baseline environment on September 25th 2005 with mean sound speed profile. The VSA was deployed with the deepest element at 40 m and the Lubell916C source was towed from a boat at 10 m depth.

Image of FIG. 8.
FIG. 8.

Sketch of the ray approached geometry of a plane wave emitted by source (S) and received by the receiver (R) at the elevation angle .

Image of FIG. 9.
FIG. 9.

Beam response at source azimuthal direction obtained using (a) the 4 -only sensors of the VSA and (b) all sensors VSA .

Image of FIG. 10.
FIG. 10.

Bottom reflection loss: deduced from the down-up ratio of the experimental data (a) and modeled by the SAFARI model (b).

Image of FIG. 11.
FIG. 11.

Measured data normalized ambiguity surfaces for sediment compressional speed during data acquisition period, for: (a) Bartlett vertical component, (b) Bartlett VSA and (c) Bartlett VSA .

Image of FIG. 12.
FIG. 12.

Measured data normalized ambiguity surfaces for sediment compressional speed and density, using the geometric mean of estimates along the acquisition period, for: (a) Bartlett vertical component only, (b) Bartlett VSA and (c) Bartlett VSA .


Generic image for table

Estimatted bottom parameters taking into account the measured VSA data on September 25th and manual adjustments on SAFARI model, considering four layer structure.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Seabed geoacoustic characterization with a vector sensor arraya)