Beyond Funneling: Subjective Experiences of Spatial Vibrotactile Feedback on the Back

Vibrotactile feedback is a common target for wearables, often making use of illusions like funneling, which produces a phantom sensation in-between actuators. However, prior work has assumed funneling produces a point sensation rather than a region across the body. To better understand how people experience spatial vibrotactile feedback, we approach this question with a qualitative study. We placed vibrotactile actuators at different locations on the back, asking participants to draw what they experienced on a map of an individual's back, and conducted open- and closed-coding analysis. Results show a range of experiences more diverse than previously described. For example, sometimes a phantom sensation was perceived in-between the actuators ("funneling"), while other times participants also indicated a region including one or both actuators (we call this "fusing"). We also document masking effects and conduction across bone and soft tissue. These findings can serve as a taxonomy guiding new research for understanding vibrotactile perception as a total experience, and provide a visual vocabulary documenting felt vibrations on the skin.