: Place your mouth against the paper and blow firmly. The air rushing through the slit will cause the paper to vibrate rapidly, creating a loud "screaming" sound. Alternative: The Paper Popper
: Use scissors to cut a small half-inch slit along the center of that fold.
: If you have a 3D printer, you can download free "screamer" whistle files from sites like Thingiverse.
: Fold the paper strip in half so the two short ends meet, and crease the fold.
: Fold about half an inch of each end of the strip outward to form a "T" or bridge shape.
: Hold the paper between your first two fingers. The flat "cross" of the T should rest against your fingertips, while the folded section with the slit sticks out between your fingers.
You can create this loud toy in seconds using a small scrap of paper.
