Adjustable Frequency PVC Horn

thingiverse

This is a basic foghorn that uses a balloon and a segment of 1/2" schedule 40 PVC. The noise is pretty loud, comparable to an automobile horn, and the frequency can be adjusted by using different lengths of PVC or by utilizing PVC with holes in it like a flute. The sound is created by blowing into the tube through the smallest hole. After printing, place a section of balloon over the largest hole and hold it in place with a rubber band. Next, insert a segment of 1/2" PVC through the middle so that it presses lightly against the balloon. I find that a 16-inch segment of PVC produces a nice foghorn-type sound. Blowing into the small hole should create noise. Troubleshooting: I had to sand the inside hole slightly to get the PVC to fit perfectly. Adjusting the tightness of the balloon and the PVC's pressure against the balloon will adjust both the volume and quality of your sound. Experiment! Teachers: I print a bunch of these for my students, then I have many pre-cut sections of PVC in the classroom. Students can experiment with different lengths and document the frequencies created. This makes for a very noisy and fun way to study sound waves! Soaking the printed plastic in disinfectant between classes eliminates any germ sharing.