From the time I was a kid, I envied people who could stick a thumb and finger in their mouth and generate an attention-getting whistle. Despite patient people trying to show me how to do it and assuring me it was "easy" -- the kiss of death -- I still don't get it. I just get hyperventilated.
I take some consolation from a bit of wood lore I learned in high school: whistling on an acorn cap. Let me warn you from the start that acorn whistles are ear-splitters. I never show people how to do it indoors. Once they get it, I shoo them far away.