Pumps and turbines experience damage by cavitation resulting in a decrease in efficiency and lifespan. Existing methods of cavitation monitoring have difficulties in distinguishing between non damaging and damaging cavitation. The newly proposed method by means of ultrasonic signals has in contrast to the existing methods the advantage that the effect of damaging cavitation can be measured close to the potentially exposed locations and is therefore not disturbed by other effects or filtered by long signal propagation paths. The feasibility of the use of ultrasound for monitoring (and possibly influencing) purpose is therefore examined and tested at suitable test objects. If the results with the test objects at the cavitation test rig at the EPFL and at the hydraulic laboratory at the HSLU are successful, the method will be applied to model test turbines and pumps.