Browsing CMRE Publications by Subject "Acoustic scattering - Seafloor and sea surface"
Now showing items 41-60 of 62
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Scattering from a rough sedimental seafloor containing shear and layering, as determined by perturbation theory
(NATO. SACLANTCEN, 1993/07)First-order perturbation theory is applied to reverberation from a rough sedimental seafloor. In addition to existing approaches, the seafloor is allowed to be shear-supporting or to be layered. Scattering strengths are ... -
Seabed characterization by inversion of parametric sonar data: selection of the cost function
(NATO. SACLANTCEN, 1997)A class of possible cost functions to be used in model-based estimation of bottom parameters from highfrequency backscatter signals is introduced. The cost is based on the properttes of the signal in the wavelettransformed ... -
Shallow-water seafloor characterization for high-frequency multibeam echosounder: image segmentation using angular backscatter
(NATO. SACLANTCEN, 1997)Sonar images from multibeam echosounders are submitted to various degradations, partly due to the sensor itself: Signal artefacts and corresponding corrections are presented, both for signal processing and for array ... -
Shallow-water sound transmission measurements taken on the New Jersey continental shelf
(NATO. SACLANTCEN, 1993/08)Calibrated acoustic measurements were made under calm sea state conditions on the New Jersey shelf near the AMCOR 6010 borehole, a surveyed area with known geophysical properties. The experiment was conducted in 73 m water ... -
Small scale volumetric inhomogeneities of shallow water sediments: measurements and discussion
(NATO. SACLANTCEN, 1997)There is a consensus that high-frequency acoustic scattering by the ocean bottom is partly due to sediment volumetric inhomogeneities, r e., random fluctuations in sediment sound speed and density. Understanding the spatial ... -
Spectral integral representations of monostatic backscattering from three dimensional distributions of sediment volume inhomogeneities
(NATO. SACLANTCEN, 2001/03)A theory is developed for generating short time, monostatic reverberation realizations caused by three dimensionally distributed volume inhomogeneities in stratified media. A spectral integral approach to treating the ... -
Spectral integral representations of scattering from volume inhomogeneities
(NATO. SACLANTCEN, 1999/07)In-situ measurements of scattering strength can be obtained by analyzing the early-time, high angle reverberation from bottom and sub-bottom features. In order to provide insight into the mechanisms which cause bottom ... -
Statistical characteristics of large-scale bottom reverberation
(NATO. SACLANTCEN, 1995/07)Simulation results from a statistical characterization of large-scale bottom reverberation from broadband signals are presented. The seafloor profile is parametrized via the surface root-mean-square height and correlation ... -
Swath bathymetry and SAS autofocus using a Chirp source
(NATO. SACLANTCEN, 1997)Swath bathymetry and SAS autofocus can both be treated as problems in correlating echoes from a scatterer distribution on the seabed. Using a chirp source, the phase derived from quadrature match-filtering can replace the ... -
Temporal fluctuation of backscattered field due to bioturbatioon in marine sediments
(NATO. SACLANTCEN, 1997)Biological activity in marine sediments creates a time-varying, randomly fluctuating medium. A bio-diffusive model is proposed for predicting the temporal and spatial spectrum of sediment density fluctuations. Perturbation ... -
Temporal modeling of high frequency (30-100 kHz) acoustic seafloor backscatter: shallow water results
(NATO. SACLANTCEN, 1997)A temporal model of high frequency seafloor acoustic backscatter is presented and compared to recorded echoes from terrigenous sediments. Using acoustic properties correlated with mean grain size, the echo shapes and ... -
Texture analysis of sidescan sonar imagery using statistical scattering models
(NATO. SACLANTCEN, 1997)It is shown that the generalised K-distribution provides a good fir to the amplrtude statisttcs of sonar imagery from several different types of seabed sediment. A number of possible explanations for the Ricean nature of ... -
The effect of water column stability on acoustic backscatter from the ocean bubble layer
(NATO. SACLANTCEN, 1997) -
The effect source movements on shallow water bottom backscatter
(NATO. SACLANTCEN, 1997)The time-evolution model BORIS is used to study the effects of source movements on bottom backscatter. Changes in the backscattend time domain signals as functions of source depth, position and incident angles are simulated ... -
The reverberation of sound from smooth ocean floors
(NATO. SACLANTCEN, 1963/02)The reverberations produced by a completely flat surface separating two homogeneous isotropic fluids is investigated. There is no effort to include the effect of rough surfaces which would be a logical extension of the ... -
The sea surface as a random filter for underwater sound waves
(NATO. SACLANTCEN, 1974/06)In this dissertation the phenomenon of scattering and reflection of underwater sound waves from the sea surface is studied by considering the surface sound channel as a random, time-dependent filter. This filter can be ... -
Theory of scattering and reflection of sound from the sea surface
(NATO. SACLANTCEN, 1975/10)Theoretical work on scattering and reflection of sound from the random timevarying rough sea surface is critically reviewed. It is shown that sound scattering from the sea surface may be treated as a purely acoustic boundary ... -
Time domain finite difference methods for range dependent Biot media
(NATO. SACLANTCEN, 1997)The physics of sound propagation in saturated, porous (Biot) media differs from propagation in fluids and elastic/anelastic solids because of the existence of a second compressional wave, the "slow" wave. Many environments ... -
Time-evolution modelling of seafloor scatter: Part 1: Theory
(NATO. SACLANTCEN, 1997/04)A time-series model for acoustic seafloor backscattering is described. -
Time-evolution modelling of seafloor scatter: Part 2: experimental verification
(NATO. SACLANTCEN, 1997/04)A time-evolution model of seafloor scatter is numerically implemented and experimentally verified. The model is based on expressing analytically the elementary time-backscattered response of every seafloor surface and every ...