Seabed Volume Scattering

The use of OASSP for computing realizations of scattering and reverberation produced by random distributions of volume inhomogeneities in the seabed is illustrated by the following example. The environment is similar to the above, but the seasurface is eliminated. The data file vol-rhs.dat for the OASP mean field is

Halfsp. Line source. Mean field. Goff. auto.
P B N s g O 
500 0
3
128.    1500      0     0     0     1      0       0
128.    1470  -2270.10  0.01  0.00  1.650  1.0000  0
228.00  2300   0000.00  0.50  0.00  2.650  0.0000  0	

100.
77. 127. 51

1200 -1200
-1 1 1 0
2048 400 600 0.0004 0 .5 2

  

Figure 7: Monostatic mean field envelope in shallow water environment with sediment layer having a strong sound speed gradient and volume inhomogeneities

The resulting depth-stacked envelope plot is shown in Fig.7.

The associated OASSP data file vol-scat.dat for calculating the field scattered is

Volume scat. Line source. . Goff-J. auto.
P N s O g  
500 0
3
128.    1500      0     0     0     1       0    0.0
128.    1470  -2270.10  0.01  0.00  1.650  -2.0 -5.0 0 2.5 1.0 0.0
228.00  2300   0000.00  0.50  0.00  2.650  0.0000 0.0 	

128.
77. 127. 51

1200 -1200
2048 1 2048 0
2048 400 600 0.0004 0 0.5 2

With the skewness set to 0 deg the main axes of the correlation function are alligned with the stratification, and the horizontal correlation length is specified to 5 m, with the vertical correlation length being 2 m. The fractal dimension of the power law spectrum (option 'g') is 2.5. The RMS relative sound speed perturbation is set to unity, while the relative density is set to 0.

  

Figure 8: Monostatic backscattering envelope in shallow water environment with sediment layer having a strong sound speed gradient and volume inhomogeneities

The resulting depth-stacked scattered field envelopes are shown in Fig.8. The fundamental differences between the scattering from seabed roughness and volume inhomogeneities is didcussed in Ref. [24].