Google Research

Soli-enabled Non-Contact Heart Rate Detection for Sleep and Meditation Tracking

  • Adam Bernstein
  • Alex Lee
  • Anupam Pathak
  • D Shin
  • David Jorgensen
  • Eiji Hayashi
  • Haiguang Li
  • Ivan Poupyrev
  • Jaime Lien
  • Jian Cui
  • Jian Wang
  • Jihan Li
  • Jin Yamanaka
  • Lauren Bedal
  • Luzhou Xu
  • Nicholas Gillian
  • Qian Zhang
  • Rajeev Nongpiur
  • Shwetak Patel
  • Trausti Thormundsson
Nature Scientific Reports (2023)


Heart rate (HR) is a crucial physiological signal that can be used to monitor health and fitness. Traditional methods for measuring HR require wearable devices, which can be inconvenient or uncomfortable, especially during sleep and meditation. Noncontact HR detection methods employing microwave radar can be a promising alternative. However, they usually use high-gain antennas and require the sensor to face the user’s chest or back, making them difficult to integrate into a portable device and unsuitable for sleep and meditation tracking applications. This study presents a novel approach for noncontact HR detection using a miniaturized Soli radar chip embedded in a Google Nest Hub. The chip has a 6.5 mm × 5 mm × 0.9 mm dimension and can be easily integrated into various devices. Our approach utilizes advanced signal processing and machine learning techniques to extract HRs from radar signals. The approach is validated on a sleep dataset (62 users, 498 hours) and a meditation dataset (114 users, 1131 minutes). The approach achieves a mean absolute error (MAE) of 1.69 bpm and a mean absolute percentage error (MAPE) of 2.67% on the sleep dataset. On the meditation dataset, the approach achieves an MAE of 1.05 bpm and a MAPE of 1.56%. The recall rates for the two datasets are 88.53% and 98.16%, respectively. This study represents the first application of the noncontact HR detection technology to sleep and meditation tracking, offering a promising alternative to wearable devices for HR monitoring during sleep and meditation.

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