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A company you have never heard of has been producing the critical element to monitor heart rate through using earbuds. Valencell currently has their code and hardware design licensed to eight different head phone manufacturers so that the users can track their workouts without having to wear a chest strip or rely on the currently not so accurate wrist based activity trackers. This makes a lot of sense when we consider that 58% of the population is already wearing eat buds when exercising and 34% wear them daily for other activities such as working around the home.
How It Works

Ear buds are a great location to track information such as heart rate, temperature and respiratory rate. The tight fit in the ear causes the sensor to have little wiggle room and any excessive motion can be easily tracked with a 3-axis accelerometer. The sensor inside the buds is measuring how light scatters off blood vessels when a small amount of light is applied to the skin. At this point a PPG or photoplethsymogram can be produced and represents the changes in blood volume. This data can be further analyzed through signal processing to show heart rate.

In a 2014 study titled Earbud-Based Sensor for the Assessment of Energy Expenditure, Heart Rate, and VO2max  showed extremely accurate results for ear based heart rate monitoring.  A -0.2% mean difference bias when compared against standard ECG and 4.4% standard deviation were found during testing.
Headphone Models

Several models of headphones are available with ear based HRM systems. They tends to range in price from $50 – $200. Some units such as the Sony B-Trainers are completely waterproof (IPX8) and can be used to monitor heart rate while swimming among other activities.
  • Bose SoundSport Pulse
  • Jabra Elite Sport
  • Jabra Sport Pulse
  • Huawei R1 Pro
  • Sony Smart B-Trainer
  • BioConnected HR+
  • LG HeartRate Earphones
  • Kuaiwear