: 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.

Making a paper "screamer" is a simple DIY project that uses air vibration to create a loud, high-pitched noise. No software download is required, as it only uses basic physical materials. How to Make a Paper Screamer

: You can find " The Simple Screamer ," a classic guide to papier-mâché, for free streaming on Internet Archive . If you'd like to try a specific style: 15 Second Paper Screamer : 4 Steps - Instructables