An active oscillation damper has a balancing mass which is movable relative to an oscillating mechanical structure. The control device then determines a compensation movement for the balancing mass based on a determined three-dimensional absolute motion of the mechanical structure. A balancing drive, arranged on the mechanical structure and acting on the balancing mass, is activated by the control device. The balancing mass is displaced by the balancing drive relative to the mechanical structure commensurate with the determined compensation movement. The measured values supplied to the control device include actual values of the balancing drive and/or a position of the balancing mass relative to the mechanical structure and/or at least one derivative with respect to time of the position of the balancing mass relative to the mechanical structure. The three-dimensional absolute motion of the mechanical structure is determined by the control device from the aforementioned values.