I wanted a usable whistle that actually works.
Sadly most emergency whistles need a lot of air and only produce really high pitched sounds.

My design was optimised to provide a low pitched sound even at minimum airflow already.
The second, high pitched sound comes on with a bit harder blow.
Combined they have matching harmonics that create a really annoying mix that is audible at great distances.
This combo works exceptionally well in areas with a lot of vegetation like a forest but also in open areas like on the water.

So, no, you won't get a fancy looking Ible, just a fancy working whistle ;)

Step 1: Design Criteria

As said, I needed something that works with low air already.
If you are in a real emergency you might not have enough strenght to perform a massive blow.
Even with normal breathing you will already get a nice sound!
This meant I had to count for size, printability as well as durability.

The basic design is like any half decent whistle and based on principles our grandfathers used already.
Only majory difference is the way the airflow is diverted to two individual whistles while also limiting the thickness of the airflow to provide a higher flow speed.
The second, high pitched sound was added to allow for much higher decibel output while also creating harmonics that result in an increased overall volume.
But basically it still comes down to: The harder you blow the louder it will be ;)

The low tone has an added resonant chamber that allows for standing wave to form inside the chamber.
With this the increased airflow when you blow hard will interrupt this standing wave.
In return it produces a humming like tone with the high frequency sound.
The sound produced when you blow hard is quite different to what you know from normal emergency whistles and really stands out.

Step 2: How to Print...

You can use any filament that is not soft or flexible.
Both PLA and ABS work fine.
I changed the keyring attachment slightly and this tiny bit is the only that needs support.
A nozzle size of 0.4mm or below is recommended.
Just load into your slicer and print with your standard settings :)

You should keep the orientation unless you want to experiment.
No real afterwork required as the print should come out clean.
Maybe a slight sanding around the mouthpiece if your printer created a slithly rough surfaceon the edges.

Step 3: Sizing...

The original size is good for everyone.
You can reduce the size by about 10% or enlarge i by up to 25% if you want to get different tones.
Smaller means higher, bigger means lower frequencies.