This can be done visually or sonically, and a whistle is a great way to inform others of an emergency without losing your voice. Even better: make your whistle out of a spend shell casing.

Learn how to create amazing bird whistle sounds using just a PVC pipe in this easy-to-follow DIY guide! With simple materials and a little creativity, you'll be able to make your own bird call ...

The telltale squashy removable pith, which makes it such an ideal whistle making material, runs through its core. Use a straight branch a bit thicker than your index finger and around ten ...