## 2aUW8. The accuracy of perturbation theory for acoustic penetration of sediment due to interface roughness.

### Session: Tuesday Morning, May 14

### Time: 10:35

**Author: Eric I. Thorsos**

**Location: Appl. Phys. Lab., College of Ocean and Fishery Sciences, Univ. of Washington, Seattle, WA 98105**

**Abstract:**

Lowest-order perturbation theory (PT) is usually considered valid for
modeling scattering from rough surfaces with a small roughness. In particular,
for PT to be accurate near the specular direction, it is required that kh<<1,
where k is the acoustic wave number and h is the rms surface height. In the case
of an acoustic wave incident on the seafloor, a rough interface will scatter
sound back into the water and also into the sediment; such scattering into the
sediment will occur even when the incident grazing angle is below the critical
angle. Here, the accuracy of PT for acoustic penetration through a rough
water/sediment interface with a power-law roughness spectrum is examined using
exact integral equation results for the 2D problem. It is found that PT remains
accurate for kh up to and well beyond unity, when the incident grazing angle is
either above or below the critical angle. The reason for this surprising result
will be discussed. [Work supported by ONR.]

from ASA 131st Meeting, Indianapolis, May 1996