UFace: Your Smartphone Can "Hear" Your Facial Expression!

Facial expression recognition (FER) is a crucial task for human-computer interaction and a multitude of multimedia applications that typically call for friendly, unobtrusive, ubiquitous, and even long-term monitoring. Achieving such a FER system meeting these multi-requirements faces critical challenges, mainly including the tiny irregular non-periodic deformation of emotion movements, high variability in facial positions and severe self-interference caused by users' own other behavior. In this work, we present UFace, a long-term, unobtrusive and reliable FER system for daily life using acoustic signals generated by a portable smartphone. We design an innovative network model with dual-stream input based on the attention mechanism, which can leverage distance-time profile features from various viewpoints to extract fine-grained emotion-related signal changes, thus enabling accurate identification of many kinds of expressions. Meanwhile, we propose effective mechanisms to deal with a series of interference issues during actual use. We implement UFace prototype with a daily-used smartphone and conduct extensive experiments in various real-world environments. The results demonstrate that UFace can successfully recognize 7 typical facial expressions with an average accuracy of 87.8% across 20 participants. Besides, the evaluation of different distances, angles, and interferences proves the great potential of the proposed system to be employed in practical scenarios.