The Refined Design Model. Low Frequency and Combined Resonances

stable component, under certain circumstances, can be formed disturbance zonez, which are referred to as caustic zones. Caustic surfaces are confocal to the inner cylindrical surface of the shell. They are formed as a by-pass of acoustic rays that are transmitted from the same point of the inner cavity of the device as a result of its circular (along the formers) and transversal (bending) oscillations. As a result it occurs a great concentration of sound waves energy in a liquid-and-stable component (Kuzmychev and Makarov, 1958; Makarov and Fadeev, 1960). The comparative analysis has revealed peculiarities of the resonant type for two design models the approximate (in the form of the elementary plate) and the refined (in the form of a shell of a considerable length) allows revealing some sufficient differences in the results (Vavylov, Peretts and Baraev, 1968; Cremer, 1955; Heckl, 1958). They were confirmed experimentally. For the refined design model we will choose a circular cylindrical shell of an unlimited length (Fig. 1). Short shells have been studied, for example, in the work (White, 1966).