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.

You get TWO whistles Color of my choice or you let me know

https://www.youtube.com/watch?v=3hDmH_TeVok&t=2s

I did not design this whistle, all attribution goes to jzisa and is licensed under the Creative Commons - Attribution license.