Design and Evaluation of Auditory Icons as Informative Warning Signals

Auditory icons – caricatures of everyday sounds – have the potential to convey information by non-verbal means quickly and accurately. Two experiments investigated the application of auditory icons as warning signals to the civil aviation cockpit environment. Warning signals that are iconic and that stand in a direct relation to the event being signalled, such as the sound of coughing to signal the presence of carbon monoxide, should convey information about the nature of the critical event as well as alerting the operator that there is a problem. By contrast, signals that are arbitrarily associated with an event, such as a beep to signal the presence of carbon monoxide, provide little information about the nature of the event. Speed and accuracy of recognition in response to these different types of warnings may also be influenced by modality (visual, auditory, auditory + visual) and by task demand (low, high). Experiment 1 investigated effects of signal iconicity (iconic, abstract), modality, and task demand on warning recognition speed and accuracy. One-hundred and seventy-eight participants completed a computer-based training session and test task that involved responding to warnings associated with nine critical events while completing low- and high-demand concurrent tasks. As hypothesized, fewer training trials were required to learn iconic warnings compared with abstract warnings. During the test phase, the effect of iconicity, as hypothesized, was influenced by modality and task demand. Bimodal (auditory + visual) warnings were recognized with the greatest consistency and accuracy. Auditory abstract warnings elicited slow reaction times and poor accuracy. Auditory iconic warnings, under conditions of high demand, evoked levels of accuracy comparable with bimodal warnings. Experiment 2 investigated recognition speed and accuracy in response to four auditory iconic and four abstract warnings in an Advanced Aviation Training Device. As hypothesized, accuracy was greater in response to auditory iconic than abstract warnings and recognition accuracy and reaction time were unaffected by level of flying experience. Reaction times in the Advanced Aviation Training Device were approximately 1 second. These initial experiments suggest that there is potential for the use of auditory iconic warnings and bimodal warnings as the means, not only to alert, but also inform pilots about the nature of a critical incident.