Designing Mid-Air Ultrasound Tactons with Spatiotemporal Parameters for Distinguishable Tactile Brushes

Mid-air ultrasound technology offers new possibilities for conveying information using spatiotemporal tactile icons (i.e., Tactons) in contactless applications. Although prior work has explored the design space of spatiotemporal parameters, their distinguishability remains underexplored. In this paper, we investigate the perceptual dissimilarity spaces of mid-air ultrasound Tactons by varying five spatiotemporal parameters to support effective tactile brush designs, which serve as the fundamental units for designing various patterns in mid-air ultrasound haptic systems. We created 36, 42, and 54 Tactons and ran three studies with 36 participants to collect similarity ratings. From the collected data, we derived perceptual spaces and analyzed them to identify the dominant parameters in each set. For instance, brush size transition (open and close) significantly contributed to distinguishability when drawing frequency was fixed but had little impact when drawing frequency was included as a design parameter. Based on the study results, we propose four design guidelines for creating distinguishable spatiotemporal ultrasound Tactons and outline directions for future research.