Uni-, bi- and tri-modal warning signals: Effects of temporal parameters and sensory modality on perceived urgency

• Higher signal rates result in higher (but not monotone increasing) perceived urgency.
• Inter pulse interval affects perceived urgency stronger than pulse duration.
• The effects of pulse duration and inter pulse interval are universal across modalities.
• Multi-modal signals are perceived as more urgent than their constituents.

Multi-sensory warnings can potentially enhance risk communication. Hereto we investigated how temporal signal parameters affect perceived urgency within and across modalities. In an experiment, 78 observers rated the perceived urgency of uni-, bi-, and/or tri-modal stimuli as function of 25 combinations of pulse duration (range 100–1600 ms) and inter pulse interval length (100–1600 ms). The results showed that perceived urgency increases with signal rate. Inter pulse interval showed a larger effect than pulse duration and the largest differences in perceived urgency as function of inter pulse interval occurred at the smallest pulse duration (100 ms). The effects of pulse duration and inter pulse interval were universal across modalities. Bi- and tri-modal signals were perceived as more urgent than each of their uni-modal constituents. We conclude that temporal parameters can be deployed to construct integrated, multi-sensory warning signals with a pre-specified degree of perceived urgency.