Home » How To's » How to Make a Telephone with Paper and Plastic Cups

How to Make a Telephone with Paper and Plastic Cups

paper cups telephone

With iPhones and Snapchat it’s difficult to imagine kids growing up without the excitement of making telephones out of paper cups and string. It seems like every childhood friendship consisted of wishing you lived close enough to each other to communicate through your bedroom windows with the latest and greatest in “cup and string telephone technology.” It made you feel like you were getting one over on your parents, while it gave you and your friend a sense of adventure and autonomy. Secret late-night chats about hypothetical missions or the latest gossip… those were the days!

Just because we have actual technology, like virtual phone numbers, that lets us do this much easier, does not mean it’s not still fun though, and making telephones is a great ways to teach kids about sound waves and how a traditional telephone works. Let’s take a look at how to make an effective cup and string telephone.

Steps to Make a Telephone out of Paper Cups and String

For materials you’ll need to buy two paper (or plastic) cups and a non-stretchable string, and you’ll need a pair of scissors. Here are the steps to make a paper cup telephone:

  1. Poke a hole in the bottom of each cup with the scissors or another small, sharp object.
    (Optional) Decorate your cups with markers to customize your own personal cup telephone.
  2. Cut the string to your desired length – we recommend you start with anywhere from 60 to 100 feet (we’ll talk about the science behind this later in the post).
  3. Thread each end of the string through the holes in the cups and tie knots in each end to prevent the string from pulling back through the cups. You may also use paper clips to keep the strings attached.
  4. Then, both you and your partner begin walking away from each other until the string is tight. Careful not to rip the string out, but you will need some tension in order for the sound waves to carry.
  5. Finally, as you hold your cup to your ear, your partner can begin sending you secret messages through their cup. Play with the length of the string to see how shorter or longer strings make the message more or less clear. Have fun!

Science Behind the Cup and String Telephone

While this activity is certainly fun and harkens childhood treehouse fantasies, it is also an excellent chance to learn about telephone technology and sound waves. We can communicate with each other because the sound waves our voices make are put out into the air around us. These waves do dissipate if directed into the air, which is why it is easier to hear people that are physically closer to us than farther away – this is why we shout from long distances.

Sounds travel between the two cups through the following process: when the first person speaks into their cup, their voice creates sound waves which then vibrate the bottom of the cup, making it move back and forth about 1000 times per second – or faster! This vibration travels down the string so long as there is tension and it is not a stretchable string (kite string or cotton twine are good ones to use). Once the vibrations reach the other cup, the second person should be able to hear what the first said. You can speak at normal volumes because the sound waves aren’t lost in the air. But, if your string becomes too long, this can also cause the sound waves to weaken and your message won’t be delivered to the other person. This is why it would be fun to experiment with string lengths to see when the message is clearest, and when it starts to fade. You can also experiment with different kinds of cups, whether they are small, big, plastic, paper, or styrofoam. All of these adjustments will affect the clarity and volume of your message.

A traditional telephone operates in much the same way as this rudimentary version. With actual telephones, an electric current replaces the string, and an aspect known as the diaphragm converts your sound waves to electrical energy, and it travels to your friend’s phone via the established telephone network. Transferring the waves to electrical energy allows the waves to travel further. This is a very oversimplified explanation, but for the sake of comparison, it accomplishes the task of comparing the transference of sound waves to a second party.

How Telephones Work Today – Softphones / Virtual Numbers

The technology we use today even with our high tech smartphones is very similar to the technology that has always existed. Instead of converting our sound waves into electrical signals, they are converted to radio signals. Then those signals are picked up by radio towers and sent to our friend’s phone, which then translates those radio signals back to sound waves.

Virtual numbers also work in a similar way. When you buy a virtual number, it is simply a number that is not assigned to a specific telephone line. Instead, these numbers are programmed to be forwarded to another established landline, cell number, or softphone. The rationale behind this is that during the week from 9-5 you can forward the number to your office phone, and on the weekends, you can forward the calls to your cell phone. The reason people find these numbers and this flexibility attractive is that you can give out a local phone number to a local business even though you may be operating your company in an entirely different locale or country. You can even use these phone numbers over the internet on your computer, so if there is no cellular service, but you have wifi, you can still dial and receive calls.

Back to the Basics

No matter how technologically advanced we become as a society, it’s fun to get back to the basics and have some good old fashioned fun with crafts and friends. It’s good to remember the basics behind some of the things we take for granted, especially with the many conveniences of modern technology. Whether you’re in a small midwestern United States town or the bustling city of Toronto, you’ll see folks walking around talking on their cell phones. It’s safe to say that a good portion of these individuals couldn’t tell you how their phones really worked. It might be time for them to sit down and make a cup and string telephone to understand the fundamentals of the amazing technology we have available at our fingertips!

Global Call Forwarding logo