Google researchers have developed a new technology called APG (Audioplethysmography) that can turn existing ANC headphones into heart monitors with a software update. The tech giant published a research paper titled “APG: Audioplethysmography for cardiac monitoring in hearable devices” detailing this new technology.

Google says APG is an acoustic sensor system that sends a low-intensity ultrasonic sound signal through the speakers of ANC headphones and headphones and picks up echoes through the built-in microphones. The company then uses a mathematical model to analyze the ultrasound echoes and convert them into heart rate readings.

Google conducted an eight-month field study with 153 participants to evaluate FPG and found it to be highly accurate in reporting heart rate readings (average error 3.21%) and heart rate variability (average error 2.70%).

The technology works to monitor heart activity even when music is played through headphones and the body moves during activities such as running.

Google is currently focusing on testing APG with more intense physical activities like walking, weightlifting, boxing, and HIIT (high-intensity interval training) to improve the technique’s performance. The company believes APG has the potential for many other exciting health research opportunities.