This tutorial contains theoretical material (the main ideas of wave processes), as well as an analysis of numerous examples and problems, which show how (in the opinion of the author) it is necessary to approach their solution. Tasks are closely related to the main text and are often its development and addition. The material of the book, as far as possible, is freed from excessive mathematization - the main emphasis is transferred to the physical side of the phenomena under consideration. For students of physical specialties of universities.