The monograph is devoted to the development of theory, computer modeling and experimental studies of sound fields in open-type layered waveguides in order to explain the characteristic features of the propagation of sound waves that have not been adequately explained in classical acoustics of layered media. As a theoretical basis, a non-self-adjoint model formulation of the key boundary value problem for hydroacoustics, set and solved in a self-adjoint model formulation in the classical works of K. Pekeris, L.M. Brekhovskikh, V.D. Krupin and V.Yu. Zavadsky, T.-F. Gao, E.-Ch. Shang.