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Doppler passive fathometry
(CMRE, 2019/05)
Passive fathometry is a technique whereby broadband ambient ocean noise received on an array of hydrophones is averaged and cross-correlated to produce a sub-bottom profile [Siderius, Harrison, and Porter (2006). J. Acoust. ...
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 ...
Separation of measured noise coherence matrix into Toeplitz and Hankel parts
(CMRE, 2017/08)
The cross-spectral density of ocean ambient noise is usually estimated from the product of the complex hydrophone signals, each of which already corresponds to the summed responses of sources from all angles. The true ...
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. ...
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 ...
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 ...
An approximate form of the Rayleigh reflection loss and its phase: application to reverberation calculation
(NURC, 2012/04)
A useful approximation to the Rayleigh reflection coefficient for two half-spaces composed of water over sediment is derived. This exhibits dependence on angle that may deviate considerably from linear in the interval ...