I've tested this print myself and it is very loud, vey fun design.
"The design is meant to look as clean and simple as possible while still looking like a whistle. It was also designed to be easily gripped with thick gloves or cold hands. It has a raised lip on the bottom and grips on the top to allow you to hold it securely in your mouth even if you are blowing as hard as you can. There is a hole in the back for a key ring or lanyard so you can wear it around your neck or attach it to your zipper or keychain.
Another huge focus in designing this was to make it printable in one piece with no supports or rafting. I wanted someone to be able to print this before going for a hike or something with no assembly, cleanup, or fuss of any kind to get it ready. Just print and go!
The whistle actually has two slightly different tones produced at the same time by separate chambers on either side. The two different tones alternate between amplifying and canceling each other out. This variation creates the shrill sound much like a pea whistle that is more attention grabbing and does not get lost as easily over background noise like a single tone whistle could. Unlike a pea whistle however it does not jam if blown too hard and will not freeze up in cold weather. I tested the volume with my decibel meter and it reached 118.7db. The harder you blow into it the louder it is so someone with a stronger lung capacity may reach louder levels. Be careful it can hurt your ears a little bit at that level."
V29 (jzisa) / CC BY 3.0