### 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
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Boris V. Kerzhakov
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*Inst. of Appl. Phys., Russian Acad. of Sci., 46, Ulyanov St., 603600
Nizhny Novgorod, Russia
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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.]