A rigid moveable sphere which is part of a mass‐spring‐dashpot system is constrained to move with one degree of freedom in an acoustical medium. The motion which ensues when the sphere is struck by a transient incident plane wave and, second, by a transient incident spherical wave, is studied. The motion of the sphere is computed and analysis is given for the inverse problem which seeks to determine the properties of the incident wave from the known motion of the sphere.