I can whistle 3 ways: the typical pucker you lips whistle, use your fingers whistle, and a third that I’ve only seen my brother and I do. For the third curl your upper lip towards your nose, bring the bottom lip up flat, move your tongue all the back and down, and try and direct the air into the split part of your inner upper lip. It’s a very loud piercing whistle that can be heard much farther than the typical finger whistle.