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Shallow water tomography with a sparse array during the INTIMATE'98 sea trial
Felisberto, P.; Jesus, S. M.; Stephan, Y.; Demoulin, X.Invert acoustic data using sparse arrays - at the limit with a single hydrophone - is a challenging task. The final goal is to obtain a rapid environmental assessment with systems both easier to deploy and less expensive than full vertical arrays. In this paper, it is shown that using a known broadband source signal and an array with few hydrophones, ocean acoustic tomography can be performed, even in a complex...
Single sensor source localization in a range dependent environment
Jesus, S. M.; Porter, M. B.; Stephan, Y.; Coelho, E.; Rodríguez, O. C.; Demoulin, X.Source localization with a single sensor explores the time spread of the received signal as it travels from the emitter to the receiver. In shallow water, and for ranges larger than a few times the water depth, the received signal typically exhibits a large number of closely spaced arrivals. However, not all the arrivals are equally important for estimating the source position since a number of them convey redu...
Estimating equivalent bottom geoacoustial parameters from broadband inversion
Demoulin, X.; Pelissero, L.; Stéphan, Y.; Jesus, S. M.; Porter, M.; Coelho, E.A simple and fast approach to retrieve equivalent geoacoustic parameters is presented in this paper. The method is based upon the processing of 300-800 Hz broadband signals on a single hydrophone.Two stable characteristics of the impulse response of the shallow water waveguide are estimated: the time dispersion and the bottom reflection amplitudes. This two features are analytically linked to the compressional ...
Nonlinear soliton interaction with acoustic signals. Focusing effects
Rodriguez, O. C.; Jesus, S. M.; Stephan, Y.; Demoulin, X.; Porter, M.; Coelho, E.The problem of nonlinear interaction of solitary wave packets with acoustical signals has been intensively studied in recente years. A key goal is to explain the observed transmission loss of shallow-water propagating signals, which has been found to be strongly time-dependent, anisotropic, and sometimes exhibited unexpected attenuation vs. frequency.
Using the echo pattern to range a sound source
Porter, M. B.; Stéphan, Y.; Démoulin, X.; Jesus, S. M.; Coelho, E.One of the currently exciting areas in SONAR research is in the use of acoustic channel models to improve SONAR systems. In this paper, we use the echo pattern at a single phone to localise a sound source in both range and depth in the ocean. To make the localisation robust, the signal processing is set-up with particular regard to which acoustic features are reliable and clear encoders of the source position. ...
Internal tide acoustic tomography: reliability of the normal modes expansion as...
Rodríguez, O. C.; Jesus, S. M.; Stephan, Y.; Démoulin, X.; Porter, M.; Coelho, E.Using hydrodynamic and thermodynamic equations appropriate for modelling internal tides, one can predict the current and temperature distributions associated with the ocean's dynamic modes. Comparing such predictions with observations from the INTIMATE'96 experiment, we nd a high degree of correlation between the rst 3 theoretically calculated dynamic modes and corresponding empirical orthogonal functions (EO...
Single-hydrophone source tracking in a variable environment
Porter, M. B.; Jesus, S. M.; Stephan, Y.; Coelho, E.; Démoulin, X.Internal tides commonly occur along ocean coasts. They are internal waves driven by the usual tidal force and generated by scattering at a sharp bottom feature such as the shelf break. The internal tides are dramatic features with crests typically 10-30 km apart and wave heights of 20 m. On the ocean surface they cause only a gentle ripple about 10 cm high but they affect the shine of the surface. As a result, ...
INTIMATE'96. A shallow water tomography experiment devoted to the study of inte...
Demoulin, X.; Stephan, Y.; Jesus, S. M.; Coelho, E.; Porter, Michael B.The INTIMATE (INternal Tide Investigation by Means of Acoustic Tomography Experiment) project is devoted to the study of internal tides by use of acoustic tomography. The first exploratory experiment was carried out in June 1996 on the continental shelf off the west coast of Portugal. A towed broadband acoustic source and a 4-hydrophone vertical array were used. Acoustic data were collected for 5 days, includin...
One-way active tracking in the INTIMATE 96 Experiment
Coelho, E.; Jesus, S. M.; Porter, M.; Stephan, Y.The acoustic data shows a clean multipath structure warped in time by the tides. Ray, mode, FFP models all provide a precise prediction of the arrival structure. The source is tracked continuously over several days as it moves to and from the array both cross−slope and down− slope. Tides cause a small wobble in apparent target range. Flat−bottom model leads to a small range error when the source moves down−slope.
Internal tide impact measured by an acoustic tomography experiment
Stephan, Y.; Demoulin, X.; Jesus, S. M.; Coelho, E.; Porter, Michael B.The INTIMATE project is devoted to the internal study of tides by the use of acoustic tomography schemes. The first exploratory experiment was carried out in June 1996 on the continental shelf off the coast of Portugal using a towed broadband acoustic source a four-hydrophone vertical array.
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