  We present ActSonic, an intelligent, low-power active acoustic sensing system
integrated into eyeglasses that can recognize 27 different everyday activities
(e.g., eating, drinking, toothbrushing) from inaudible acoustic waves around
the body with a time resolution of one second. It only needs a pair of
miniature speakers and microphones mounted on each hinge of eyeglasses to emit
ultrasonic waves to create an acoustic aura around the body. Based on the
position and motion of various body parts, the acoustic signals are reflected
with unique patterns captured by the microphone and analyzed by a customized
self-supervised deep learning framework to infer the performed activities.
ActSonic was deployed in a user study with 19 participants across 19 households
to evaluate its efficacy. Without requiring any training data from a new user
(leave-one-participant-out evaluation), ActSonic was able to detect 27
activities, achieving an average F1-score of 86.6% in fully unconstrained
scenarios and 93.4% in prompted settings at participants' homes.
