Find an empty plastic bottle. You can use a film container, a small hotel shampoo bottle or a small plastic pop bottle. The smaller the bottle the higher the pitch of the chirping sound. Get someone to help you cut a slot into the side of the bottle. If it is a film container make the slot 3 cm X 1/2 cm (1" X 3/16"). If you are using a 500 ml (12 oz) bottle of pop make the slot approximately 10cm X 1cm (4" X 3/8"). Make a hole in the lid big enough to stick a piece of string through. Tie the string with the knot on the inside of the container. When you twirl the container around the air rushes into the slot and makes a whistling sound. A small container sounds like a little bird chirping. A large family size pop bottle sounds like a big bullfrog.