ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

1pAO12. Investigation of the layered bottom structure influence on propagation of high-frequency acoustic signals.

Margarita S. Fokina

Boris V. Kerzhakov

Inst. of Appl. Phys., Russian Acad. of Sci., 46, Ulyanov St., 603600 Nizhny Novgorod, Russia

Peculiarities of frequency-angle dependences of Frenel's reflection coefficients V(fd,(theta)) (f=frequency, d=layer thickness, (theta)=grazing angle) from a system of elastic layers on the elastic substrate is investigated. The method of calculating the phase and the module of the reflection coefficient from the layered elastic absorbing substrate is numerically realized. The resonant behavior of the reflection coefficient at different grazing angles for a given bottom model is investigated. The influence of the set of parameters of bottom layers and the substrate on the frequency-angle dependence of the reflection coefficient and the behavior resonance of the reflection coefficient is considered. The effects of the layer structure of the elastic absorbing bottom on the space-frequency dependences of acoustic fields in oceanic waveguides in the frequency range 20--1000 Hz is studied. The relationship between the type of sediments that forms bottom layers and frequency ranges, where the least losses due to propagation are observed, i.e., optimum propagation frequencies, is ascertained. [Work supported by RFFI project N 94-05-1725-a.]