An electromagnetic sound generator has a vibrating plate mounted in a case. A plurality of operating cylinders have pressure spaces which are flow-connected to the channels for moving the pressure rollers inward and outward in order to press coverings onto a printing unit cylinder. The external coating of the foot is constituted by a single piece that completely covers the internal cylinder. The simulation model may be stochastic, may be updated from monitoring the external system or the simulations, or may contain a Bayesian network .