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Xiaoran "Van" Fan

Xiaoran "Van" Fan

Van is an Experimental Scientist at Google, Technology Directions Office, Sensor Intelligence Team. He is interested in hearables, including audio architectures, signal processing algorithms, and software-hardware co-design for novel applications. Van is an experimentalist and system builder. He is enthusiastic about real-world-experiment-driven research.
Authored Publications
Google Publications
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    Exploring the Feasibility of Remote Cardiac Auscultation Using Earphones
    Tao Chen
    Yongjie Yang
    Xiuzhen Guo
    Jie Xiong
    Shangguan Longfei
    MobiCom 2024: The 30th Annual International Conference On Mobile Computing And Networking
    Preview abstract The elderly over 65 accounts for 80% of COVID deaths in the United States. In response to the pandemic, the federal, state governments, and commercial insurers are promoting video visits, through which the elderly can access specialists at home over the Internet, without the risk of COVID exposure. However, the current video visit practice barely relies on video observation and talking. The specialist could not assess the patient's health conditions by performing auscultations. This paper tries to address this key missing component in video visits by proposing Asclepius, a hardware-software solution that turns the patient's earphones into a stethoscope, allowing the specialist to hear the patient's fine-grained heart sound (i.e., PCG signals) in video visits. To achieve this goal, we contribute a low-cost plug-in peripheral that repurposes the earphone's speaker into a microphone and uses it to capture the patient's minute PCG signals from her ear canal. As the PCG signals suffer from strong attenuation and multi-path effects when propagating from the heart to ear canals, we then propose efficient signal processing algorithms coupled with a data-driven approach to de-reverberate and further correct the amplitude and frequency distortion in raw PCG receptions. We implement Asclepius on a 2-layer PCB board and follow the IRB protocol to evaluate its performance with 30 volunteers. Our extensive experiments show that Asclepius can effectively recover Phonocardiogram (PCG) signals with different types of earphones. The feedback from cardiologists also confirms the efficacy and efficiency of our system. PCG signal samples and benchmark results can be found at an anonymous link https://asclepius-system.github.io/ View details
    APG: Audioplethysmography for Cardiac Monitoring in Hearables
    David Pearl
    Rich Howard
    Longfei Shangguan
    Trausti Thormundsson
    MobiCom 2023: The 29th Annual International Conference On Mobile Computing And Networking (MobiCom), Association for Computing Machinery (ACM) (to appear)
    Preview abstract This paper presents Audioplethysmography (APG), a novel cardiac monitoring modality for active noise cancellation (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. We observed that, as the volume of ear canals slightly changes with blood vessel deformations, the 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. We conducted an eight-month field study with 153 participants to evaluate APG in various conditions. Our studies conform to the (Institutional Review Board) IRB policies from our company. The presented technology, experimental design, and results have been reviewed and further improved by feedback garnered from our internal Health Team, Product Team, User Experience (UX) Team and Legal team. Our results demonstrate 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. View details
    Design Earable Sensing Systems: Perspectives and Lessons Learned from Industry
    Trausti Thormundsson
    Adjunct Proceedings of the 2023 ACM International Joint Conference on Pervasive and Ubiquitous Computing and the 2023 ACM International Symposium on Wearable Computers, ACM (to appear)
    Preview abstract Earables computing is an emerging research community as the industry witnesses the soaring of True Wireless Stereo (TWS) Active Noise Canceling (ANC) earbuds in the past ten years. There is an increasing trend of newly initiated earable research spanning across mobile health, user-interfaces, speech processing, and context-awareness. Head-worn devices are anticipated to be the next generation Mobile Computing and Human-Computer Interaction (HCI) platform. In this paper, we share our design experiences and lessons learned in building hearable sensing systems from the industry perspective. We also give our takes on future directions of the earable research. View details
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