What is it about?
APG (Audioplethysmography) is a novel technology for ANC headphones; APG sends a low intensity ultrasound probing signal using an ANC headphone's speakers and receives the echoes via the on-board feedback microphones. As the volume of ear canals slightly changes with blood vessel deformations, a user's heartbeats will modulate these ultrasound echoes. We built mathematical models to analyze the underlying physics and propose a multi-tone APG signal processing pipeline to derive the heart rate and heart rate variability in both constrained and unconstrained settings. APG enables robust monitoring of cardiac activities using mass-market ANC headphones in the presence of music playback and body motion such as running.
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Why is it important?
Our findings show that APG achieves consistently high HR (3.21% median error across 153 participants in all scenarios) and HRV (2.70% median error in interbeat interval, IBI) measurement accuracy. Our UX study further shows that APG is resilient to variation in: skin tone, sub-optimal seal conditions, and ear canal size. Finally, APG is a software based technology that can be applied to ANC headphones via a software update, thereby creating the possibility for implementation on older and newer devices, turning millions of headphones into health sensing devices.
Perspectives
Where many innovations in health-tech research require new hardware to work, the beauty in APG lies in its "relative simplicity" and implementation as software that can function on millions of pre-existing devices. Working on developing the technology and writing this article allowed a very unique collaboration between experimental science and UXR (User Experience Research) - on one hand we got to develop a ground-breaking technology, and on the other we matched the technology to a growing need (lower cost and more accurate health sensing), all while having a truly career-changing experience of trying a new technology on people for the very first time... and having it work! I hope this paper and the technology inspires new innovation in the mobile health sensing space and serves to enable lower cost sensing of physiological signals for communities around the world (e.g. a phone, watch, and earbuds could now or in the near future, provide health telemetry equivalent to what you might get with other previously inaccessible medical technology).
David Pearl
Tufts University
Read the Original
This page is a summary of: APG: Audioplethysmography for Cardiac Monitoring in Hearables, October 2023, ACM (Association for Computing Machinery),
DOI: 10.1145/3570361.3613281.
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