mHealth Tympanometer

A handheld tympanometer for low-resource settings — the instrument an audiologist uses to test middle-ear function, rebuilt to be affordable for all. Current tympanometers range anywhere from $500 to $5000, and the goal of the project was to make it somewhere around the $50 price range. It is NIH-funded work in the mHealth Lab at Duke, it has been field-tested in South Africa, and it is still under active development. The project is intended to be open source, and when it is, I will update here with the gitlab links.

During my research stint in the mHealth lab, I was the sole developer for the firmware. The device works by playing a probe tone into the ear canal while a linear actuator sweeps the pressure inside it. A microphone listens, the signal is reduced to an envelope point at each pressure step, and the curve those points trace out is a tympanogram — the thing a clinician actually reads. I created this curve by leveraging a state-machine approach to ensure the order of operations: initialize, idle, detect a seal in the ear, acquire, transmit, return to idle, with distinct error paths for a seal that never forms, a seal lost mid-sweep, and a measurement that overruns. It then sends all of the information via bluetooth to an Android application.

My other contribution was a toolchain migration. The board existed as an Altium project and needed to become a KiCad one — one main board, six schematic sheets covering power, the microcontroller, the sensor front end, the motor driver and audio. The repository carries both toolchains for the same design, which is the migration in evidence, with backups dated across autumn 2023. Footprints and 3D models are the usual casualties of a port like this, and there were around twenty-five embedded component models on the Altium side to account for.

The device itself is not mine to show, this was a team effort, with arguably the best team I've worked with to date! You can read this article about me and the team, and our efforts on the project. an article about the project