Sound scattering by rough elongated elastic objects. II: Fluctuations of scattered field

Sonar echoes from unresolved features of rough objects tend to interfere with each other. Because of these interferences, properties of the echoes, such as its envelope level, will vary from realization to realization of stochastically rough objects. In this article, the nature of the fluctuations of the backscattered echo envelope of rough solid elastic elongated objects is investigated. A general formulation is initially presented after which specific formulas are derived and numerically evaluated for straight finite‐length cylinders. The study uses both the approximate modal‐series‐ and Sommerfeld–Watson‐transformation‐based deformed cylinder solutions presented in the first part of this series [T. K. Stanton, J. Acoust. Soc. Am. 92, XXX (1992)]. The fluctuations of the backscattered echo envelope are related to the Rice probability density function (PDF) and shown to depend upon σ/a and L/L in the Rayleigh scattering region (ka≪1) and kσ and L/L in the geometric region (ka≫1), where σ is the rms rough...