This is a remix of the Flat Pocket Whistle by Jonas Daehnert.

His whistle was already only 3mm thick but I have slit it in half to be even thinner and given it a frame the size of a credit card so that you can keep it in your wallet or purse.

Still Printing mine but I am reasonably sure it will work as long as you pinch the two halves tightly together.

Will make changed based on user input and my own experience.

UPDATE 070723: So I have been playing with this and it sort of works. Let me first state the the concept itself works flawlessly. A whistle split in half and held together works correctly with almost no noticeable difference from the whole whistle. The problem is that when you print the two halves separately the printed surface is not smooth enough to seal correctly. So what can we do?

As far as the original model goes, you can sand it a little with a nail file. It doesn't take much and then it works.

That being said, I am not ready to give up on print in place. I think if you printed it upside down on a smooth or glass bed then it would work correctly. I am also playing around with the current orientation trying to make it work on textured beds.

UPDATE2 070723: After printing about a dozen of these, I have added an improved model. Still working on print in place but this model reduces sanding significantly…Just 3 passes with a nail file was enough to make it work. It would also probably work if resin printed or if you had an extremely well calibrated FDM machine.