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The Sound of One Hand: A Wrist-mounted Bio-acoustic Fingertip Gesture Interface. Brian Amento, Will Hill AT&T Labs – Research Loren Terveen University of Minnesota. Outline. Motivation Gesture Interfaces Signal Classifiers Prototype Applications Future Work. Motivation.
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The Sound of One Hand:A Wrist-mounted Bio-acoustic Fingertip Gesture Interface Brian Amento, Will Hill AT&T Labs – Research Loren Terveen University of Minnesota
Outline • Motivation • Gesture Interfaces • Signal Classifiers • Prototype Applications • Future Work
Motivation • Small wearable digital devices increasingly popular (Cellphones, PDAs, Rios, etc..) • Nonlinear access to linear media will increase • Voicemail, Music, Video, Radio, Text • Controls: Device Select, Play, Stop, Scan forward, Scan backward, Faster, Slower, Item Select, Exit
Current Interfaces to Mobile Devices • Two-handed control mechanisms • Pressing device buttons • Writing/selecting with stylus • Un-holstering a wearable is a pain (i.e., wristwatches beat pocket watches) • Speech recognition • Noise or social setting may rule out voice control • Our Goal: Invisible, weightless, un-tethered and cost-free
Body tracking Polhemus 2000 Teresa Martin 1997
Image hand tracking Cullen Jennings, 1999
Our Approach “Natural” fingertip gestures
What’s “natural” • Small - max displacement of 5 cm • Gentle, < 10% of pressing strength (e.g. no finger snap) • Few gestures, little memory work • Avoid ring and pinky finger • Examples: • Thumb as anvil - index, middle as hammer • Thumbpad to fingerpad • Thumbpad to fingernail edge
Fingertip Gestures • Tap, double tap • Finger and thumb pads rub • Money gesture and reverse • Finger and thumb pads press • Soft Flick
Fingertip Gesture Interface • Wristband-mounted piezo-electric contact microphones positioned on the styloid bones • Sense bone conducted sounds produced by gentle fingertip gestures
Simple Classifier • Allows real-time analysis and control • 800 samples every 10th of a second • Take max absolute, quantize to 10 levels • Finite state machine outputs Taps and Rubs • Intermediate states filter background noise • Buffer states allow continuous gestures • Surprisingly accurate: ~90%
More Sophisticated Classifier • Noticeable differences in audio signals • Hidden Markov Models • Gesture and noise models trained with sampled data • Confidence levels for each trained gesture
HMM Classifier Accuracy • Using 3 subjects, collected 100 instances of gestures rub, tap and flick • 80 used for training, 20 for testing
Wrist Display Prototype • Timex Internet Messenger watch • Tap to cycle through messages • Double-tap to rewind
Other Prototypes • Cellphone dialing application • Rub scrolls list in one direction • Tap dials phone number • Powerpoint slide control • Tap moves forward one slide • Double tap moves back
Future Work • Miniaturization of device • Hitachi SH5 controller • Improved gesture classifiers • Finger Identification • Analyze signals from multiple microphone locations • User Studies • Usefulness: Compare performance to current cellphone, PDA and desktop control interfaces. • Social impact: Study how users exploit private control techniques to mobile devices
Conclusion • Fingertip gestures • sensed acoustically at the wrist • can be communicated wirelessly to nearby devices • show promise as a control method.