ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06
4pUW10. The influence of sediment scattering and variability on acoustic
intensity including data comparisons.
Keith J. Howell
Melvin J. Jacobson
William L. Siegmann
Rensselaer Polytech. Inst., Troy, NY 12180-3590
William M. Carey
Adv. Res. Projects Agency, Arlington, VA 22203-1714
Previous work [Howell et al., 2928 (1994)] has shown that
statistics of multimodal intensity could be matched using a three-layer
isospeed model that included effects of scattering. To more accurately estimate
scattering effects on intensity over a broad frequency range, additional bottom
information must be included. In this paper, an analytic treatment of a shallow
channel consisting of n isospeed layers is developed for a wide-angle PE
propagation model. A scattering layer is introduced at a horizontal
water-bottom interface to model effects of attenuation due to interface and
sediment scattering. The local mean of intensity is determined and its
sensitivity to parameters such as the number of layers, frequency, scattering
layer thickness, and correlation length of inhomogeneities is investigated. The
standard deviation of intensity is also examined. Comparisons are made between
intensity statistics for the multilayer models and depth-dependent profile
models consistent with data from a New Jersey Shelf experiment. Additional
emphasis is directed toward the number of isospeed layers needed to match
experimental intensity over a range of frequencies. [Work supported by ONR.]