A four tone whistle.
A whistle with a loop.
A decently loud whistle.
Be aware of that last point before you give one to your kids.
This model is printable without any support material.
The printing orientation is optimized for air-tightness.
Thus potentially porous sound damping bridging of ceiling planes is fully avoided.
The print-layers are parallel to the air channel
The inner barrel surface is shaped such
that sharp kinks are minimized.
In the current design
the lower bottom of the air channel lines up with
the center of the air splitting blade.