Ear We Go Again

Earbuds do a lot more than just play music these days. They have picked up so many new capabilities that an entirely new category of electronic devices known as earables has been created to describe them. Due to their close proximity to the body, they are especially promising for applications in health monitoring. And since so many people now wear earbuds much of the day, this monitoring is both continuous and transparent.

There is a downside to using this platform, however. To be acceptable to users, earables need to be very, very small. That means, of course, that all of the hardware supporting the device’s many capabilities must also be packed into an extremely tiny space. Many engineering challenges arise when designing and producing devices of this sort. The expertise and costs required to solve these problems greatly limits who can get in on the game. As such, there are only a small number of capable earables on the market today.

A group led by researchers at the Karlsruhe Institute of Technology in Germany is working to make the barriers to entry lower in this area. We previously reported on their efforts to develop an open source earphone platform called OpenEarable that simplifies developing hardware capable of physiological ear sensing. Now they have extended that platform with OpenEarable 2.0, which packs in even more hardware. This updated version of the system can be used to track more than 30 metrics that are valuable in health monitoring.

OpenEarable 2.0 is designed to look and feel like a standard pair of Bluetooth earbuds, but under the hood it is packed with sensors. The device integrates two ultrasound-capable microphones (one facing inward toward the ear canal and one facing outward), a 3-axis accelerometer that doubles as a bone-conduction microphone, a 9-axis inertial measurement unit for detecting head movements, a pulse oximeter, optical temperature sensor, and an ear canal pressure sensor. All of this is managed by an onboard microcontroller and supported by a rechargeable battery that can run for up to five hours with all sensors active.

Despite this complexity, the platform was designed from the ground up to be open, extensible, and affordable. The entire hardware design — down to the printed circuit boards and 3D-printable case — is open source and built using freely available design tools. Off-the-shelf components are used wherever possible, and no specialized manufacturing equipment is required.

The wide range of sensing options enables many applications. In the area of health monitoring, the device can track heart rate, blood oxygen levels, body temperature, and even subtle movements of the ear canal that may correspond to chewing, talking, or facial expressions. For activity tracking, it can record head movements and overall body motion. Beyond health and fitness, the combination of sensors could enable novel forms of human-computer interaction, biometric authentication, and even cognitive or emotional state monitoring.

By combining high-end sensing capabilities with open source accessibility, OpenEarable 2.0 offers a flexible foundation for researchers and developers exploring the future of wearable computing. It makes it possible for anyone with curiosity and a bit of experience with electronics to join in shaping what earables can do next.