Perception of ultrasonic haptic feedback on the hand

Ultrasonic haptic feedback is a promising means of providing tactile sensations in mid-air without encumbering the user with an actuator. However, controlled and rigorous HCI research is needed to understand the basic characteristics of perception of this new feedback medium, and so how best to utilise ultrasonic haptics in an interface. This paper describes two experiments conducted into two fundamental aspects of ultrasonic haptic perception: 1) localisation of a static point and 2) the perception of motion. Understanding these would provide insight into 1) the spatial resolution of an ultrasonic interface and 2) what forms of feedback give the most convincing illusion of movement. Results show an average localisation error of 8.5mm, with higher error along the longitudinal axis. Convincing sensations of motion were produced when travelling longer distances, using longer stimulus durations and stimulating multiple points along the trajectory. Guidelines for feedback design are given.