AI Wearables Glossary: 30+ Terms You Need to Know
From HRV to PPG to OTC — every AI wearable term explained in plain English.
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In this article
Sensor Terms
- PPG (Photoplethysmography)
- Optical sensor that measures blood flow changes by shining light into the skin. Used in smart rings and smartwatches for heart rate, HRV, and SpO2 measurement.
- SpO2 (Blood Oxygen Saturation)
- Measure of oxygen in your blood. Normal range is 95–100%. Drops during sleep can indicate sleep apnea.
- Accelerometer
- Sensor that measures motion. Used in smart rings for sleep stage detection and activity tracking.
- Gyroscope
- Sensor that measures rotation. Used in smart glasses for head tracking and gesture detection.
- Infrared Sensor
- Sensor that uses infrared light (invisible to humans). Smart rings use IR PPG sensors which work better in the dark than the green LEDs in smartwatches.
Health Metrics
- HRV (Heart Rate Variability)
- Variation in time between heartbeats. Higher HRV = better recovery. Lower HRV = stress, illness, or overtraining. Single best objective measure of recovery.
- RHR (Resting Heart Rate)
- Your heart rate when fully at rest. Lower RHR generally indicates better cardiovascular fitness. Sudden RHR elevation can indicate illness.
- Sleep Stages
- The four stages of sleep: awake, light sleep, deep sleep (N3), and REM sleep. Each stage has distinct physiological characteristics.
- Deep Sleep (N3)
- The most physically restorative sleep stage. Most adults should get 15–25% of sleep in deep stages. Critical for physical recovery.
- REM Sleep
- Stage associated with dreaming and memory consolidation. Adults should get 20–25% of sleep in REM.
- Readiness Score
- Oura's 0–100 metric combining HRV, sleep, temperature, and RHR. Tells you whether to push hard or recover.
- Resilience
- Oura's long-term stress/recovery tracking metric. Shows how your body responds to stress load over time.
Audio Terms
- Open-Ear Audio
- Speaker design that delivers sound to your ear without blocking outside noise. Used in smart glasses for safety (you can hear traffic).
- Speaker Diarization
- AI feature that distinguishes who said what in a recording. Used by Plaud Note for meeting transcription.
- Tinnitus Masking
- Feature in hearing aids that generates white noise to mask tinnitus (ringing in the ears). Available in Lexie B2 Plus.
Regulatory Terms
- OTC Hearing Aid
- Over-the-counter hearing aid for adults 18+ with mild to moderate hearing loss. FDA-cleared, no prescription required. Available since August 2022.
- FDA-Cleared
- Device that the FDA has reviewed and determined to be "substantially equivalent" to a previously cleared device. Required for OTC hearing aids.
- HIPAA
- Health Insurance Portability and Accountability Act. Regulates how health data is handled. Applies to employer wellness programs using AI wearables.
- GDPR
- General Data Protection Regulation. EU law governing data privacy. Oura is GDPR-compliant (data stored in Finland/EU).
Frequently Asked Questions
HRV (Heart Rate Variability) is the variation in time between heartbeats. Higher HRV indicates better recovery; lower HRV indicates stress, illness, or overtraining. HRV is the single best objective measure of recovery and is tracked by all major smart rings.
OTC (Over-the-Counter) hearing aids are FDA-cleared medical devices for adults 18+ with mild to moderate hearing loss. They don't require a prescription or audiologist visit. The FDA created the OTC hearing aid category in August 2022, making hearing aids significantly more affordable.