Abstract
A series of three studies examined the acoustic characteristics that contribute to a sound being unambiguously perceived as an urgent alarm within a vehicle context. In experiment 1, participants sorted a variety of sounds modeled after sounds currently in use in driver-vehicle interfaces (DVIs) into categories indicating highly critical warnings and alerts (or “alarms”), vehicle status sounds, or in vehicle social notifications. Results indicated that four criteria (peak-to-total time ratio, interburst interval, number of harmonics, and base frequency) explained 61% of the variance in categorization. From these criteria, cutoffs were determined and manipulated to create stimuli for an initial validation study. Experiment 2 results indicated that these criteria remained robust even when examined in a larger stimulus set and with different participants. Finally, Experiment 3 investigated rapid categorization under divided attention. Participants categorized alerts while driving in a desktop driving simulator and completing a secondary distracting task. Results indicate that previously defined parameter criteria and cutoffs are applicable in higher context and under load. Furthermore, sounds that met all criteria were responded to more quickly than those which met only some or no criteria, indicating that these criteria can be used to create sounds which are unambiguous and intuitive in an in-vehicle driving context.