This is a simple keychain whistle. I really liked the whistle by Tohmis, which was a redesign of https://www.thingiverse.com/thing:3130078, but I find the high pitched whistles hard on my ears. So with that as inspiration, I redesigned it into a single side with a longer resonance tube so that it now sounds more like a train whistle and is easier on my ears. This one is not as loud as the original, but it was a fun little project to try.