Whistling Nose Cone for Compressed Air Rocket

This is an updated version of this compressed air rocket nose cone : http://www.thingiverse.com/thing:120753. As the name suggests, this one whistles. It has a good pitch, especially accelerating down from the apex. I will continue to work on this to make it louder. I have included a cross-section. Maybe someone knows more about whistles than me?

The last picture is the the rocket after 3 launches. The last impact was straight down from ~3-400 feet up. The plastic is intact; ready to have a n