Unlocking Practical Cardiac Monitoring Capabilities on True Wireless Stereo Earbuds

Abstract

The human ear presents unique physiological and practical advantages for cardiac monitoring. However, existing ear-able systems rely on extra hardware and complex processing, making them unsuitable for resource-constrained True Wireless Stereo (TWS) earbuds. We present EarCardio, a system that repurposes the built-in IMU sensors of commercial TWS earbuds for cardiac monitoring. Our key insight is that the built-in IMUs can capture ballistocardiogram (BCG) signals, which are streamed to a smartphone via Bluetooth for processing. EarCardio enhances the low-rate and unreliable IMU data through multi-axis fusion and signal enhancement, and further reconstructs fine-grained seismocardiogram (SCG) signals using a region-focused translation framework. We implement EarCardio as a real-time system and evaluate it with 110 human subjects. Results show that EarCardio accurately reconstructs cardiac signals and remains robust to motion artifacts, missing data, and low sampling rates, thus enabling a wide range of cardiac monitoring applications.