Establishing Vibration-Based Tactile Line Profiles for Use in Multimodal Graphics

<jats:p>Vibration plays a significant role in the way users interact with touchscreens. For many users, vibration affords tactile alerts and other enhancements. For eyes-free users and users with visual impairments, vibration can also serve a more primary role in the user interface, such as indicating streets on maps, conveying information about graphs, or even specifying basic graphics. However, vibration is rarely used in current user interfaces beyond basic cuing. Furthermore, designers and developers who do actually use vibration more extensively are often unable to determine the exact properties of the vibration signals they are implementing, due to out-of-the-box software and hardware limitations. We make two contributions in this work. First, we investigate the contextual properties of touchscreen vibrations and how vibrations can be used to effectively convey traditional, embossed elements, such as dashes and dots. To do so, we developed an open source, Android-based library to generate vibrations that are perceptually salient and intuitive, improving upon existing vibration libraries. Second, we conducted a user study with 26 blind or visually impaired users to evaluate and categorize the effects with respect to traditional tactile line profiles. We have established a range of vibration effects that can be reliably generated by our haptic library and are perceptible and distinguishable by users.</jats:p>