Smart backup alarms react to the environment. Via a built-in microphone, these warning sounders permanently measure the volume of the ambient noise. A built-in microprocessor then automatically adjusts the volume of the warning tone so that it is only about 5 dB above the measured level. This ensures that the warning tone is always loud enough to be heard by everyone in the danger zone. At the same time, however, it prevents the warning tone from being perceived as too disturbing, especially in quiet surroundings.