You can 3D print your own train whistle now. Your neighbors will love it.

Maker AeroKoi has designed a modular, 3D printable train whistle, complete with adjustable bell caps that let you tune the notes it plays. The design is an evolution from earlier, larger-diameter whistles, requiring less air and allowing you to replicate specific chime patterns from classic steam-era trains, like the Santa Fe 5 chime, using a provided spreadsheet of measurements. It's a clever bit of hobbyist engineering that dives into the physics of sound waves, explaining the differences between resonant-chamber whistles and diaphragm-based horns.

The project is a delight for railfans and makers who want a loud, customizable noisemaker, but it comes with a catch: you'll need a serious air compressor with a large tank to get more than one short toot. For everyone else, it's a perfect recipe for turning your workshop into a minor public nuisance. The takeaway? Sometimes the coolest projects are the ones that let you annoy people with historically accurate sound effects.