Could whistle normally as long as I can remember. Tried forever to learn the two finger loud whistles as a kid and never could make a sound but still tried. I still recall when I was around 13 yo reading Goosebumps and randomly did the gesture when suddenly I made the first successfull attempt. I literally turned to the mirror on the side becuase of the surprise and had that Shaq face on Hot Ones. After practicing for a while I discovered that, while you can whistle EXTREMELY loudly this way, you legit hurt your own eardrums the most. Basically kamikaze whistling. I don’t use it that often because of it.
The third way of whsitling is by blowing through your palms which makes that owl-like howl. You can basically do the first part of the song in Once Upon a Time in the West this way.
Also, snapping your fingers in a very “snappy” loud and deep kinda way.
Atlantis