An audio unit, connected or connectable to a safety-critical apparatus, or integrated or integrable in the apparatus, is proposed. The audio unit may comprise a driver unit, a detection unit, and an alert unit. The driver unit may generate an analog audio signal in response to a request from the apparatus, to drive an acoustic output unit and thereby generate an acoustic signal for a user of the apparatus. The detection unit may detect the audio signal. The alert unit may generate an alert signal in response to the request if the detection unit has not detected the audio signal. It can thus be checked whether the acoustic signal is generated. A method for generating a safety critical acoustic signal is also described.