My freshman fall, I was enrolled in ENGR100 project. I was put into a sustainable medical technology subsection. My team built a low-cost acoustic spirometer to diagnose chronic respiratory disease. I led early prototyping, researching microphones that could capture high-frequency tones from airflow through a vortex whistle. Most options wouldn't arrive in time or meet our 20 kHz requirement, so we selected the Adafruit MAX4466 for its sensitivity and Arduino compatibility. Research confirmed that a vortex whistle converts airflow directly into measurable frequency, allowing us to translate a user's breath into data.
The first 3D-printed whistle had critical flaws: internal supports blocked the air path and low infill caused leakage. Initially, I tried using epoxy to seal the gap, and even though it worked, I realized that doing that every time isn't viable. I reprinted with no supports and higher infill, and simultaneously designed my own whistle based on the research article's exact geometry. After several iterations, I produced a functioning whistle generating frequencies above 9 kHz with only minor leakage that could be sealed.
I prepared the breadboard layout and Arduino code framework, designed LED and housing components, and soldered the MAX4466 microphone after proper training. The first image shows the rough setup of the breadboard pre-solder. The second is the onshape CAD file of the housing unit, and the third image is a snippet of the basic code.
Over 20 hours of prototyping through multiple design cycles, we built a working device with a reliable whistle, functional LED mounting plate, and complete housing. This video shows users blowing into the whistle and receiving instant visual feedback—green, yellow, or red lights indicating respiratory function.