Even today's kids, used to smartphones with dozens of advanced features, can enjoy the classic tin-can telephone. This simple do-it-yourself toy uses basic principles of acoustics to connect two users through a length of string. To make this toy, you'll need two clean tin cans without lids, a nail, a hammer and a length of string.
Prepare Your Cans
Place the nail in the center of the bottom of the first can and lightly tap a hole in it using the hammer. If the can has jagged edges where the lid was removed, you don't want little ones putting it to their faces; wrap the edges in duct tape to blunt them. Repeat this process for the second can. Allow kids to personalize the cans by decorating them with stickers, markers or paint.
Add the String
Feed one end of the string through the hole in each can. Tie a knot in the end so that the string won't slip back out through the hole. You should now have one can attached to each end of the string. Any length of string can work, but a length of 10-30 feet is ideal; the string needs to be taut for the phone to work well, making longer lengths a challenge.
Using the Phone
To speak through the tin-can phone, children should move apart until the string is taut. One child speaks into the can at one end, while the other listens. The sound waves created by speech cause the can to vibrate. This in turn causes the string to vibrate. When these vibrations reach the can at the far end, it also vibrates, acting like a speaker to transmit the sound.