Abstract: Spherical bodies, such as bearing balls, are tested for machining irregularities or structural defects by subjecting them to supersonic vibrations from two or more ultrasound generators through the intermediary of a coupling liquid in which these bodies are immersed. One ultrasound generator has an axis in line with the body being tested while the other generator or generators have axes including acute angles with the radial directions of that body. The body is subjected to rotation in different planes by injecting the coupling liquid, alternately or simultaneously but at varying relative rates, through two different nozzles into an interspace separating the body from a spherically concave supporting surface.