The monograph is devoted to physical and electrodynamic methods of studying multilayer structures. In the fourth part of the monograph, specific methods have solved the problems of propagation of one-dimensional waves during a normal fall on a structure consisting of a different number of media. The paper presents the methods of averaging, exclusion and rearrangement. The averaging method obtained averaged boundary conditions, found amplitudes of reflected and passing waves for three and four media with arbitrary parameters. Exclusion method found amplitudes of incoming and outgoing waves. The complete procedure of consecutive substitutions and the scheme of numerical implementation of the exclusion method. are given. Considered cases of two to five, as well as an arbitrary number of media. By the method of reflections, the fall of directly and backward directed waves to a structure consisting of three media is considered. The amplitudes of external and internal waves, reflection and passage coefficients. are determined. Comparison of results with direct method. The monograph will be useful for students and graduate students of physical specialties of universities and institutes, as well as teachers, engineers and researchers in the field of technical sciences .