A device for controlling a passenger protection system of a motor vehicle includes at least one structure-borne noise sensor, used to receive body vibrations, and an evaluation device, used to evaluate the structure-borne noise signal. The evaluation provides information about an impact object and/or the characteristics of the impact. The evaluation device is configured to analyze the structure-borne noise signal in relation to the frequencies contained therein, wherein the frequency spectrum contained in a signal section is distributed into a plurality of frequency ranges. The current signal energy is determined for each frequency range, and the signal energy of the frequency range is a standardized. The device also comprises a passenger protection system, which can be actuated according to the information relating to the impact object and/or the characteristics of the impact. Further, the evaluation device is embodied such that during standardization, the signal energy of each frequency range is established in relation to the signal energy of a specific reference frequency range, and the resulting ratio course is compared to predetermined threshold values.