## 5aUW7. Computations of rough surface reflection coefficients in a waveguide.

### Session: Friday Morning, December 6

### Time: 9:16

**Author: David H. Berman**

**Location: Dept. of Phys. and Astron., Univ. of Iowa, Iowa City, IA 52242**

**Abstract:**

The effect of rough interface scattering in a waveguide is complicated by
the possibility of scattered sound returning to the rough interface and then
rescattering. A formalism for determining the effect of such rescattering on the
mean field was developed in a previous paper [D. H. Berman, J. Acoust. Soc. Am.
96, 417--426 (1994)], and similar formalisms are described in A. G. Voronovich
[Wave Scattering from Rough Surfaces (Springer-Verlag, Berlin, 1994)]. It has
been argued that the effect of re-scattering will be small if the skip distance
of rays associated with normal modes is larger than the correlation length of
surface roughness. Using numerical evaluations of the Bourret approximation for
the mean field, it is shown here that for correlation lengths comparable to the
skip distance, rescattering can contribute significantly to the effective
reflection coefficient for the mean field. However, it will also be shown that a
good approximation to the effective reflection coefficient can be obtained by
replacing the true surface roughness by a multiple of the surface roughness. The
multiple is determined by the ratio of skip distance to correlation length.
[Work supported by ONR.]

ASA 132nd meeting - Hawaii, December 1996