The monograph contains an exposition of the basic laws of propagation of flat elastic waves in crystals of different symmetry. Unlike conventional methods of presentation, direct (uncoordinated) methods of vector and tensor calculus are used here. The main attention is paid to the consideration of general methods of solving relevant problems, but the methodology of specific calculations is also described in detail .. The book can be useful for scientific and engineering workers specializing in the practical use of elastic waves in crystals, as well as a manual for undergraduate and graduate students of the crystal physics specialty.