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Now showing items 21-30 of 77
Sound absorption by suspended particulate matter
(NATO. SACLANTCEN, 1997)
A series of experiments has been performed to study the viscous absorption of sound by particulate suspensions typical of those found in coastal waters. The effect due to the particles in the frequency range of 50 - 150 ...
Relating in situ shear wave velocity to void ratio and grain size for unconsolidated marine sediments
(NATO. SACLANTCEN, 1997)
Recent advances in field hardware have meant that it has become possible to measurein situ shear wave velocity in the upper few decimetres of sea floor sediment in a routine manner. It is known that shear wave velocity can ...
Physics of bottom scattering and some applications
(NATO. SACLANTCEN, 1997)
The main bottom scattering theories are described in their bistatic formulation: composite-roughness, and volume scattering. Several applications are proposed. One of the main concerns is to check the mono- and bisfafic ...
Acoustic signal dispersion and distortion by shallow undersea transmission channels
(NATO. SACLANTCEN, 1997)
The undersea littoral is an adverse medium for acoustic signal transmission to horizontal ranges of many water depths. Reflections and scattering in the bounded, nonhomogeneous channel disperse the arrivaj of received ...
Advances in cots side scan sonar for MCM applications
(NATO. SACLANTCEN, 1997)
The Persian Gulf War has elevated the awareness to the problems of shallow water mine detection. Today's high technology shallow water anti-invasion mines, such as the Italian made "MANTA" and the Swedish manufactured ...
Bayesian inference and sidescan restoration
(NATO. SACLANTCEN, 1997)
We consider a Bayesian approach to the problem of inferring parameters of the SONAR environment given only the gathered sidescan image. A simplified model of the process is developed along with suitable distributions on ...
Source and receiver responses in boreholes
(NATO. SACLANTCEN, 1997)
This report considers the acoustic interaction between the acoustic freld rn a borehole and the elastic field in the surrounding formation. The problem with acoustic-seismic radration of energy from a source in a fluid ...
Shallow-water coherence of broadband signals
(NATO. SACLANTCEN, 1997)
The frequency-dependent spatial and temporal variabilities of sound propagation in coastal regions is investigated by ezperiment and numerical simulations. Experimental observations show that temporal coherence of the ...
Numerical modelling of acoustic scattering by smooth inclusions in a layered fluid-solid medium
(NATO. SACLANTCEN, 1997)
A boundary integral equation (BIE) method as descnbed for computing the scattering of a monofrequent acoustic field by a smooth, rigid 30 object in a layered range-independent fluid-solid medium. The BIE is discretized ...
Critical angle and seabed scattering issues for active-sonar performance predictions in shallow water
(NATO. SACLANTCEN, 1997)
Active sonar performance predictions (0.75 to 3 kHz) are examined in summer shallow-water environments to quantify the impact of variable seabed and watermass properties on detection. Scattering is computed with an ...