On the theory of self-action of ultrasonic and hypersonic waves

The self‐action of ultrasonic and hypersonic waves in a homogeneous medium is investigated. It is proved, that the mathematical technique used for the description of the self‐focusing of laser beams is applicable to the treatment of thermal self‐focusing (self‐defocusing) of sound waves including the wave propagation in a solid medium and taking account of diffraction effects. The values of critical powers are estimated. The equation for dimensionless width of the beam is derived with regard for the elastic nonlinearity of a medium and its solution is obtained by a Taylor series expansion. The conditions of self‐focusing of ultra‐ and hypersonic wave beams are given. [Russian Text Ignored].