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Now showing items 51-59 of 59
AUV active perception: exploiting the water column
(CMRE, 2019/06)
Autonomous Underwater Vehicles (AUVs) present a low-cost alternative or supplement to existing underwater surveillance networks. The NATO STO Centre for Maritime Research and Experimentation is developing collaborative ...
High-speed simulation of an underwater acoustic field using an array processor
(NATO. SACLANTCEN, 1979/12)
A computer model PAREQ for simulating the acoustic field of sound propagating in a complicated ocean environment has been installed on a realtime computer system (HP MX21) which includes an array processor (MAP 300). The ...
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 ...
Comparison of CONGRATS ray tracing predictions with MEDUSA measurements of reverberation
(NATO. SACLANTCEN, 1971/12)
From the user's point of view, ray tracing is just a computer procedure which is inserted into larger programs of different degrees of complexity . The following table indicates in which kind of programs this procedure is ...
Multipath field representation for seabed parameter extraction using backscatter data from shadow zones
(NATO. SACLANTCEN, 1997)
Inversion strategies for bottom parameter estimation in shallow water impose stringent requirements on accuracy and speed of acoustic models. We highlight the importance of second order effects as first order determinants ...
A solution of of the wave sound equation in shallow water for real speed profiles and solid bottom under sediment
(NATO. SACLANTCEN, 1975/10)
The wave equation has been solved by using normal mode theory. The medium is assumed to be horizontally stratified. A closed form solution has been found in the case of GANS - PEDERSEN types of density and sound-speed ...
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 ...
Ocean-bottom reflectivity (a point of view)
(NATO. SACLANTCEN, 1975/10)
The analysis procedures for extracting bottom loss values from pulsed acoustic signals that have interacted with the ocean bottom do not inherently consider sub-bottom refraction and reflection of sound, which are important ...
Influence of background-noise spatial coherence on high-resolution passive method
(NATO. SACLANTCEN, 1982/06)
New signal processing methods for passive listening have appeared recently : they are called "high resolution" methods because they have theoretically a better resolving power than conventional or adaptive beamforming . ...