FIELD: physics, measurement.
SUBSTANCE: invention concerns testing physical properties of materials and is intended for determination of sound wave speed in mono and polycrystals. Substance of invention involves preliminary determination of crystal lattice period for mono and polycrystal by x-ray method, and further sound wave speed is defined by the formula: 
where Vsw is sound wave speed in mono and polycrystal; m is atomic mass of chemical elements; e is electron charge; r is distance between closest adjoining atoms depending on type and period of crystal lattice a0; π=3.14; ε0 is electric constant.
EFFECT: expanded functional capacities, reduced labour cost.
