1. Method of quality control in ultrasound welding, in which a measured value tolerance range is determined from measured values from executed welding processes, said measured values being associated with at least one parameter that influences the welding process and/or represents the quality of the welding process, wherein measured values that are assigned to the same parameter in subsequent welding processes are taken into consideration in quality control, characterized in that, based upon deviations of the subsequent measured values from the tolerance range established using the previous measured values, the measured value tolerance range for subsequent welds is adjusted in terms of its configuration or in terms of its position in relation to a mean value.