Mapping candidate within-vehicle auditory displays to their referents

OBJECTIVE: This study investigated speech, environmental sounds (naturally occurring sounds with arbitrary meanings), auditory icons (natural or synthetic sounds with specific meanings), and abstract synthetic warnings as candidates for within-vehicle interfaces. BACKGROUND: Auditory displays and warnings must satisfy certain criteria, such as being appropriately urgent and commanding appropriately fast response times. However, a semiotic analysis suggests that displays, as signals interpreted by users, should also be mapped successfully onto their referents. METHOD: Response times and accuracy were recorded in a computer task of identifying learned mappings of candidate displays to a range of referent driving events (such as "headway closing"); perceived urgency and pleasantness were assessed separately. RESULTS: Speech and auditory icons produced near-ceiling performance in response times and identification accuracy. Abstract sounds produced notably slower response times and less accuracy. Environmental sounds showed an intermediate pattern of performance for accuracy, but the response times were similar to those of the abstract sounds. Speech utterances were similarly and consistently rated as pleasant but also of intermediate perceived urgency. The three other sound types showed a consistent mapping of their perceived urgency to the situational urgency of their referents; for these sounds, perceived urgency and pleasantness were negatively correlated. CONCLUSION: The results point to the importance of considering the role of signal-referent relationships in designing auditory displays. APPLICATION: The results have applicability for auditory displays in the vehicle interface, whereas the theoretical framework is of value in auditory display design in a broader context.