Naoki Kimura (The University of Tokyo, Bunkyo, Tokyo, Japan)Tan Gemicioglu (Georgia Institute of Technology, Atlanta, Georgia, United States)Jonathan Womack (Georgia Institute of Technology, Atlanta, Georgia, United States)Yuhui Zhao (Georgia Institute of Technology, Atlanta, Georgia, United States)Richard Li (University of Washington, Seattle, Washington, United States)Abdelkareem Bedri (Carnegie Mellon University, Pittsburgh, Pennsylvania, United States)Zixiong Su (The University of Tokyo, Tokyo, Japan)Alex Olwal (Google Inc., Mountain View, California, United States)Jun Rekimoto (The University of Tokyo, Tokyo, Japan)Thad Starner (Georgia Institute of Technology, Atlanta, Georgia, United States)
Speech is inappropriate in many situations, limiting when voice control can be used. Most unvoiced speech text entry systems can not be used while on-the-go due to movement artifacts. Using a dental retainer with capacitive touch sensors, SilentSpeller tracks tongue movement, enabling users to type by spelling words without voicing. SilentSpeller achieves an average 97% character accuracy in offline isolated word testing on a 1164-word dictionary. Walking has little effect on accuracy; average offline character accuracy was roughly equivalent on 107 phrases entered while walking (97.5%) or seated (96.5%). To demonstrate extensibility, the system was tested on 100 unseen words, leading to an average 94% accuracy. Live text entry speeds for seven participants averaged 37 words per minute at 87% accuracy. Comparing silent spelling to current practice suggests that SilentSpeller may be a viable alternative for silent mobile text entry.