Perceptive aspects of emergency signals

In Germany, reference time signals from an atomic clock are distributed via a long-wave radio station called DCF77. As a rule, both radio clocks and wrist watches set their actual time as well as the switching between summer and winter time using the DCF77. Apart from this service which started in the 1970ties, more recently studies are underway how to use the spare bits of the time code for civil protection emergency signals. A possible realization could be that emergency signals are radiated from smoke detectors. In the framework of such a scenario, the suitability of different pure tone signals as emergency signals was studied in psychoacoustic experiments. The effects of different durations and repetition rates were assessed using the methods of random access as well as semantic differential. For the selection of the signals, the hearing ability in an ageing population was also taken into consideration. Moreover, signals were tailored in such a way to minimize possible confusions with other signals from alarm clocks, smoke detectors etc. In the lecture, signals will be presented acoustically: on the one hand, signals which are most suitable for the intended purpose, and on the other hand signals which are less appropriate.