### ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

## 5aUW8. Effect of surface height distributions on underwater acoustic
backscattering statistics.

**Kyle M. Becker
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*Graduate Program in Acoust., Penn State Univ., Appl. Res. Lab., Student
Area, P.O. Box 30, State College, PA 16804
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A problem of interest to ocean environmental acousticians is understanding
the relationship between ocean surface characteristics and acoustic
backscattering statistics. Recent experimental work has focused on determining
surface properties which cause backscattering strength statistics to deviate
from exponential. Using the nomenclature of Ogilvy (Theory of Wave Scattering
from Random Rough Surfaces, 1991) several scattering surfaces have been
fabricated. Surfaces were modeled using a moving average technique with
prescribed distribution functions and correlation functions C(R). Representing
surface elevation, h, as a continuous random process, the moving average
process of order N is given as h[sub n]=(summation)[sub l=0][sup N]w[sub
l]u[sub n-1]. Statistical properties of h are determined by the random
uncorrelated variables, u[sub n], and the choice of weights, w[sub l]. Weights
are determined by the choice of C(R) and corresponding correlation length,
(lambda)[sub 0], or distance over which C(R) decays by 1/e. Isotropic and
anisotropic surfaces have been constructed for both Gaussian and non-Gaussian
surface height distributions. Acoustic backscattering results are presented for
three cases: case I---log-normal height distribution in x and y, equal
correlation lengths; case II---Gaussian height distribution, correlation length
in y equal to ten times that of x; case III---Gaussian height distribution in
x, log-normal distribution in y, equal correlation lengths.