How Sounds Travels Through a String Telephone
two 5-ounce (150-mL) paper cups
20 feet (6m) of #10 crochet string
2 small metal paper clips
1. Use the pencil to make a small hole in the bottom of one of the cups.
2. Thread the end of the string through the hole and into the cup. Tie this end of the string to one of the paper clips.
3. Repeat steps 1 and 2, using the free end of the string and the remaining cup and paper clip.
4. With you holding one cup and your helper holding the other, walk away from each other so that the string attached to the cups is tight.
5. Ask your helper to hold the cup over his or her ear as you speak into your cup. Repeat this step by holding the cup over your ear and asking your helper to speak into his or her cup.
The person with the cup over his or her ear hears what is being said into the other cup.
Sound is produced when things, such as the string and the cup in this experiment, vibrate (to move back and forth or up and down). In this experiment, the speaker’s voice make the cup being spoken into vibrate. These vibrations travel along the string to the other cup, causing the second cup and the air inside the cup to vibrate. The vibrating air enters the ear causing the person’s eardrum to vibrate. The vibrations continue to be passed along. Nerves inside the ear send a message to the brain about the vibrations. The brain interprets the message as certain sounds. Thus the speaker’s voice is heard.
When you speak into a landline telephone, you are not causing telephone wires on the poles outside to vibrate. Instead, the vibrations caused by your voice are changed into electrical signals. The signals travel along wires from the mouthpiece of one telephone to the earpiece of another telephone, where the signals are changed back to sound.
Cell phones are not connected to wires. Instead, cell phones change the vibrations of your voice into radio waves. These waves do not material to move from one place to another. They can and do travel through space. Radio waves are a type of radiation that comes from the Sun. To help direct the signals, special towers with receiving and sending devices are positioned at various distances from each other. This is how your voice can be transferred long distances.
For more information about the making of a string telephone as well as more information about sound, see: