This takes practice, but it’s worth it!
Make an “OK” sign with your thumb and index finger. Place your fingertips together under your tongue, about half an inch in.
Curl your tongue back over your fingers. Close your lips over your fingers, leaving just a small gap. Blow hard—not out, but DOWN over your tongue.
Adjust your fingers and tongue position until you hit that sweet spot.
When you get it, you’ll produce an ear-piercing whistle that can be heard from blocks away!