These instruments were used in ancient Mexico and they require a lot of pressure to produce their screaming sounds. You really have to blow as hard as you can. So, designing my own and adapting it to work as a projectile took a ton of research and inevitable failures. After about 10 designs, each with a different intake shape, chamber volume, angle of the resonance chamber, and outlet. None of them were working when fired, and I was about to give up. Then I accidentally broke the tapered intake cone off of one of my failed designs leaving just a small hole at the top. This was what it needed to get sufficient airflow. A small inlet and an exhaust hole large enough to match. One thing that becomes apparent is that when these are traveling around 200 feet per second, the human-like agonizing shriek becomes more like a high pitched howl. likely because the increased pressure as well as vortices created outside of the projectile affecting the turbulence inside the chamber.