Google has shared a post revealing a new process using ultrasound to measure heart rate with audioplethysmography (APG) that works by bouncing low-intensity ultrasound inside the ear canal.
Scientists employed the ANC microphones to identify changes on the skin’s surface as blood flows through it.
Currently, tracking heart rate via photoplethysmography (PPG) is the most prevalent, which uses sensors on smartwatches, where light is refracted through flowing blood.
The new finding by Google could theoretically be added to any noise-cancelling earbuds via a simple software update.
“APG transforms any TWS ANC headphones into smart sensing headphones with a simple software upgrade, and works robustly across various user activities,” the Google blog post said.
“The sensing carrier signal is completely inaudible and not impacted by music playing.”
ANC tech is traditionally used for other reasons. However, the results look promising. With around 153 participants, Google shared a median error of only 3.21% for calculating heart rate, and 2.7% for heart-rate variability.
Courtesy of Google
Even with a poor ear seal, the findings were still pretty good. Differing ear canal proportions and different skin tones also did not make a difference. This was a surprising find because light-based sensors have generally been less strong on darker skin or tattooed skin.
Loud surroundings can affect this, and the APG signal can also be “heavily disturbed by body motion,” which is not ideal for runners who could gain the most from the technology.
With multiple frequencies, researchers say this problem could be rectified.
“We can use the multi-tone APG as a calibration signal to find the best frequency that measures heart rate, and use only the best frequency to get high-quality pulse waveform,” the blog said.
Despite the technological breakthrough, this type of measuring can not happen 24 hours a day, so wrist-based wearables are still preferred because of how comfort factors into the equation.
Perhaps, Google will release a new blog post soon describing how to utilise APG technology best, but as for now, news on this has yet to surface.
