reflect_loss_eckart Class Reference
[Ocean Boundaries]

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Detailed Description

Models ocean surface reflection loss using Eckart's model.

\[ RL = -20 \: log_{10} \left( exp[ - 0.5 \Gamma^2 ] \right) \]

\[ \Gamma = 2 k h sin(\theta) \]

where $ k = \frac{2 \pi f}{c} $ = wave number (1/m), $ f $ = signal frequency (Hz), $ c $ = speed of sound (m/sec), $ h $ = RMS height of wave spectrum (m), $ \theta $ = grazing angle (rad), $ \Gamma $ = Rayleigh roughness parameter, and $ RL $ = reflection loss (dB). Eckart's model arises from a Kirchhoff approximation to scattering and the assumption of a Gaussian probability of surface elevations of standard deviation h.

Jones et. al. has shown that many of the terms in this expression can be simplified if we assume that the speed of sound is 1500 m/s and that the wave height is related to wind speed by a Pierson-Moskowitz spectrum for fully developed, wind driven seas.

\[ RL = 8.6x10^{-9} f^2 w^4 sin^2(\theta) \]

where $ w $ = wind speed (m/sec).

References:
Adrian D. Jones, Janice Sendt, Alec J. Duncan, Paul A. Clarke and Amos Maggi, "Modelling the acoustic reflection loss at the rough ocean surface," Proceedings of ACOUSTICS 2009, Australian Acoustical Society, 23-25 November 2009, Adelaide, Australia.
References:
C. Eckart, “The scattering of sound from the sea surface,” J. Acoust. Soc. Am. 25, 560–570 (1953).

Constructor & Destructor Documentation

reflect_loss_eckart ( double  wind_speed  )  [inline]

Initializes ocean surface reflection loss using Eckart's model.

Parameters:
wind_speed Wind_speed used to develop rough seas (m/s)

Member Function Documentation

virtual void reflect_loss ( const wposition1 location,
const seq_vector frequencies,
double  angle,
vector< double > *  amplitude,
vector< double > *  phase = NULL 
) [inline, virtual]

Computes the broadband reflection loss and phase change.

Parameters:
location Location at which to compute reflection loss.
frequencies Frequencies over which to compute loss. (Hz)
angle Grazing angle relative to the interface (radians).
amplitude Change in ray intensity in dB (output).
phase Change in ray phase in radians (output). Hard-coded to a value of PI for this model. Phase change not computed if this is NULL.

Implements reflect_loss_model.


Member Data Documentation

const double _wind_speed2 [private]

Wind speed squared (m/sec)^2.


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