Audio-tactile displays to improve learnability and perceived urgency of alarming stimuli

Based on cross-modal learning and multiple resources theory, human performance can be improved by receiving and processing additional streams of information from the environment. In alarm situations, alarm meanings need to be distinguishable from each other and learnable for users. In audible alarms, by manipulating the temporal characteristics of sounds different audible signals can be generated. However, in some cases such as in using discrete medical alarms, when there are too many audible signals to manage, changes in temporal characteristics may not generate discriminable signals that would be easy for listeners to learn. Multimodal displays can be developed to generate additional auditory, visual, and tactile stimuli for helping humans benefit from cross-modal learning and multiple attentional resources for a better understanding of the alarm situations. In designing multimodal alarm displays in work domains where the alarms are predominantly auditory-based and where accessing visual displays is not possible at all times, tactile displays can enhance the effectiveness of alarms by providing additional streams of information for understanding the alarms. However, because of low information density of tactile information presentation, the use of tactile alarms has been limited. In this thesis, by using human subjects, the learnability of auditory and tactile alarms, separately and together in an audio-tactile display were studied. The objective of the study was to test cross-modal learning when messages of an alarm (i.e. meaning, urgency level) were conveyed simultaneously in audible, tactile and audio-tactile alarm displays. The alarm signals were designed by using spatial characteristics of tactile, and temporal characteristics of audible signals separately in audible and tactile displays as well as together in an audio-tactile display. This study explored if using multimodal alarms (tactile and audible) would help learning unimodal (audible or tactile) alarm meanings and urgency levels. The findings of this study can help for design of more efficient discrete audio-tactile alarms that promote learnability of alarm meanings and urgency levels.