## 5pPA9. The inherent background in acoustic wave scattering by a submerged target.

### Session: Friday Afternoon, May 17

### Time: 4:15

**Author: Myoung Seon Choi**

**Author: Young Sang Joo**

**Author: Jong Po Lee**

**Location: Nondestruct. Eval. Team, Korea Atomic Energy Res. Inst., P.O. Box 105, Yusong, Taejon 305-600, Korea**

**Abstract:**

A new concept for the background in resonance scattering of acoustic waves
by a submerged target is proposed. The idea is that the remainder after removing
only the resonances from the target response must be used as the background. The
complex wave numbers whose imaginary parts are the attenuation coefficients of
elastic bulk waves in target are introduced to damp out the resonances. From the
assumption that the structural damping coefficient, the product of the
attenuation coefficients of elastic bulk waves, and the outer radius of target,
is a large constant compared with the radiation damping coefficients of
resonances, a simple mathematical expression is derived for elastic cylindrical
shells and named the inherent background. It is shown that the inherent
background leads to the impenetrable (i.e., rigid or soft) background in some
limiting cases and also describes exactly the background of elastic shell over
entire frequencies regardless of shell thickness.

from ASA 131st Meeting, Indianapolis, May 1996