Beat Whistle

I am interested in creating small functional things, particularly when I can demonstrate some interesting quirk of maths or physics. This whistle produces two tones in close proximity, with the resultant noise having a pulsing buzz, similar to that of a pea whistle (but without the pea).

Model files and OpenSCAD source for this design can be found here:

https://www.printables.com/prints/79399-beat-whistle