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A theoretical model for the backscattering strength of a composite roughness sea-surface
(NATO. SACLANTCEN, 1974/02)
The surface-backscattering strength is calculated according to Rayleigh theory for surface excursions much smaller than the sound wavelength. By taking into account of self-shadowing and modulation of grazing angles, the ...
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 ...
Model for the frequency spread of backscattered underwater sound based on the facet model of the rough sea surface
(NATO. SACLANTCEN, 1978/11)
A theoretical model for the doppler spread of backscattered acoustic waves from the rough sea surface is described on the basis of the decomposition of the continuous sea-surface spectrum that leads to the concept of facets. ...
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 ...
Vertical porosity and velocity fluctuations in shallow-water surficial sediments and their use in modeling volume scattering
(NATO. SACLANTCEN, 1997)
Variability in sediment porosity and velocity creates volume scattering which is a parameter used in high-frequency scattering models. High-resolution vertical profiles of sediment porosity and compresstonal wave velocity ...
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 ...
A unified model for seabed volume and roughness scattering
(NATO. SACLANTCEN, 1997)
Seabed scattering is considered taking into account perturbations of different type: volume inhomogeneities and roughness of the interfaces. A description is given in terms of plane waves. The first-order perturbation ...
A theoretical model for doppler spread of backscattered sound from a composite roughness sea surface
(NATO. SACLANTCEN, 1975/10)
For calculating the Doppler spread of acoustical reverberation from the sea surface, good results are achieved by applying a composite-roughness model. The small wavelets primarily responsible for the backscattering are ...