Clicks are in the Air: How to Support the Interaction with Floating Objects through Ultrasonic Feedback

Gestural interfaces are increasingly integrated in human-machine interfaces, but they often rely on visual and auditory feedback and neglect the haptic channel. With technologies providing tactile feedback in midair becoming more mature, it is important to investigate their specific properties. In this paper, we focus on pointing gestures and the combination with floating displays, more precisely tapping buttons. We report the results of a user study investigating in detail different parameters of feedback created through ultrasonic transducers. The results show that the feedback is perceived as most suitable when a modulation frequency of about 150--200Hz is used, which confirms the findings on sensitivity for vibro-tactile stimuli on surfaces. The duration of the signal of either 50 or 130ms did not have a significant effect. Moreover, we present a questionnaire consisting of word pairs to rate the subjective perception of haptic characteristics, to provide a basis for future research.