In ultrasonics, spherical waves are often encountered in addition to plane waves. We have already encountered such waves in our analysis of the scattering of ultrasound by spherical particles, cavitation processes, and radiation pressure. Spherical waves are formed in the far zone of real plane ultrasonic radiators, as well as in the near zone of spherical radiators. For this reason, in this chapter we shall study separately the characteristics and singularities of the propagation of spherically symmetric waves, i.e., waves whose acoustic parameters depend on the distance from a center.