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A noise directionality model including variable bathymetry
(NATO. SACLANTCEN, 1997)
In this paper we investigate the noise directionality due to distributed surface sources m several envtronments with a uniformly sloping sea bed. Of particular interest are frequency dependence and the question of the ...
Geoacoustic inversion using multipath pulse shape
(NURC, 2008/09)
Experimental data, measured in a shallow water region of the Mediterranean Sea, are used to show that the variation of received intensity with time is well described by existing expressions [Harrison and Nielsen, J. Acoust. ...
Signal and reverberation formulae including refraction
(NATO. SACLANTCEN, 2003/04)
Because reverberation is an incoherent process it is possible to base realistic solutions on very simple flux theory. This report extends the closed-form signal and reverberation formulae of an earlier report [SACLANTCEN ...
Multipath pulse shape in a refracting environment
(NURC, 2007/11)
Multiple boundary interactions in shallow water propagation introduce a more or less Gaussian angle distribution at a distant receiver. When all paths are added the result is 'mode-stripping', i.e. the steep rays are ...
Ray convergence in a flux-like propagation formulation
(CMRE, 2014/01)
The energy flux formulation of waveguide propagation is closely related to the incoherent mode sum, and its simplicity has led to development of efficient computational algorithms for reverberation and target echo strength, ...
Multipath pulse shapes in shallow water: theory and simulation
(NURC, 2007/04)
In shallow water propagation the steeper ray angles are weakened most by boundary losses. Regarding the sound intensity as a continuous function of angle it can be converted into a function of travel time to reveal the ...
SUPREMO: a multistatic sonar performance model
(NATO. SACLANTCEN, 2002/11)
Multistatic sonars introduce new problems to the modeller such as mutual interference from multiple sources and variable target aspect in a background of range-dependent bistatic reverberation. A multistatic sonar performance ...
The relation between the waveguide invariant, multipath impulse response, and ray cycles
(NURC, 2012/04)
The waveguide invariant, b, that manifests itself as interference fringes or "striations" in a plot of frequency vs source-receiver separation, is usually thought of as a modal phenomenon. This paper shows that striations ...
A relation between multipath group velocity, mode number, and ray cycle distance
(CMRE, 2014/01)
Weston's ray invariant or "characteristic time" in a range-dependent environment is exactly equivalent to the Wentzel-Kramers-Brillouin phase integral for ducted normal modes. By considering a ray element it is shown that ...
Target time smearing with short transmmissions and multipath propagation
(NURC, 2012/04)
In active sonar the target echo level is often estimated with a propagation model that adds all multipath arrivals. If the (post-correlator) transmitted pulse is short compared to the multipath time spread then there is ...