Google’s ANC Earbuds: More Than Just Noise Cancellation
Google has recently unveiled its groundbreaking research into audio plethysmograph (APG), a technology that can transform active noise canceling (ANC) headphones and earbuds into heart rate monitors without the need for additional hardware. This is achieved through a simple software upgrade.
The Science Behind It
The ear canal, according to Google, is an optimal location for health sensing. This is because the deep ear artery forms a complex network of smaller vessels that extensively permeate the auditory canal. The APG method involves sending a low-intensity ultrasound probing signal through the speakers of an ANC headphone. This signal produces echoes, which are then picked up by on-board feedback microphones. These echoes are modulated by the tiny displacements of the ear canal skin and heartbeat vibrations.
Google has developed a model that processes this feedback to provide a heart rate reading. It can also measure heart rate variability (HRV). Impressively, this technique remains effective even when music is playing or if the earbuds don’t have a perfect seal. However, body motion can affect the readings. To counteract this, Google introduced a multi-tone approach that acts as a calibration tool. This tool identifies the best frequency for measuring heart rate and uses it to obtain a high-quality pulse waveform.
Research Findings
Google conducted two studies involving 153 participants. The results showed that APG consistently provides accurate heart rate readings with a median error of 3.21% across various activity scenarios. The median error for HRV measurements was 2.70%. One of the standout features of this technology is that it’s not affected by skin tones, ear canal size, or imperfect earbud seals. Google asserts that this method is superior to traditional photoplethysmograms (PPG) and electrocardiograms (ECG) sensors, which are typically integrated into headphones or earbuds. The traditional approach adds to the cost, weight, power consumption, and design complexity of the devices.
The Future of APG
APG has the potential to revolutionize the way we view ANC headphones. With just a software upgrade, these headphones can be transformed into smart sensing devices. The sensing carrier signal is inaudible and remains unaffected by music. Google believes that APG opens up new avenues in biomedical and mobile research, offering a cost-effective solution for health sensing.
It’s worth noting that APG is a collaborative effort involving Google Health, product, UX, and legal teams. However, its integration into Pixel Buds is still uncertain.
Related: Google researchers transform ordinary ANC earbuds into heart rate monitoring device
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