This is an extremely loud airhorn that's easy to print. I have found it very useful for waking up friends, and for pretending to be a bus on the street. This is based on the design of an airhorn I saw being sold on the street near Fisherman's Wharf in San Francisco. The geometry is simple and clever. After your print it, just add a balloon and a rubber band, and you're good to go! https://youtu.be/XzplgTAGIUg Made in OnShape: https://cad.onshape.com/documents/fc84b201b8f848d88d5030201) Print using 100% infill, no supports. 2) Stretch a piece of rubber over the top part and secure with a rubber band. A balloon or a condom both work well. Trim the excess. 3) Blow through the triangle hole! You may want earplugs.