The analysis of a spherically converging sound beam is made. As the parameter reflecting evolution of a wave, the front surface curvature is used. The expressions are received, allowing determining value of a phase front curvature of sound beams with various amplitude distributions. Axial and cross distributions of front curvature of focused beam with gauss and uniform amplitude distributions are resulted. Different influence of radiator surface curvature on wave front dynamics in cases ,  and  is marked. Similar characteristics for a flat radiator are presented. 

Keywords: Focusing radiator; diffraction; phase front curvature