Extra tiny whistle, easily printable (ideally at a layer height of 0.2 mm) with a loop for hanging.

If the whistle does not work for you, try rotating it so that the bridges inside the whistle look like this:

See also:

Membrane Whistle

https://www.printables.com/cs/model/952885-membrane-whistle

Finger Wind Surf

https://www.printables.com/cs/model/945450-finger-wind-surf