[Physics] I made a tin can phone using a plastic slinky and paper cups. Why didn’t it work

Question

After watching some videos on Khan academy in regards to the information theory, I spent a few minutes creating a primitive "tin can phone." The materials of my phone are a plastic slinky and two paper cups.

I pierced the bottom of both cups with the edges of the slinky and tried communicating with my partner a few metres away. It was a total failure.
Also, I tried strumming the string, but, again, the sound didn't reach the other side.

An explanation of the how and why this happened and maybe some tips for next time would be great.

Answer 1

I am basing this almost completely on the comments above and my own experience of making a "tin can phone" as a kid.

The string was pulled as tight as we could get it, on the basis that a loose string, i.e. no tension, would not carry the sound waves very far.

But the tension in the string also makes the base of the cup vibrate, increasing your chances of getting your shouting into your "phone" being carried down the wire and setting up matching vibrations on the base at the far end.

So, in theory at least, you shout into the phone, the base of the cup vibrates in a certain pattern, the tense string carries that pattern down to the base of the other cup, and it vibrates in the same pattern.

In reality, as far as I remember, I had to shout soooo loud that the other guy could hear me anyway, phone or no phone.

Tin Can Phone: Wikipedia

Sound waves are created as the air vibrates in response to a person's speech or other sounds. A second person's ear collects these sound waves and converts them into nerve impulses which their brain interprets as sound. In normal speech these waves travel through the air, but with a tin can telephone the waves are transmitted through an additional medium of cups and string.

When the string is pulled taut and someone speaks into one of the cans, its bottom acts as a diaphragm, converting the sound waves into longitudinal mechanical vibrations which vary the tension of the string. These variations in tension set up longitudinal waves in the string which travel to the second can, causing its bottom to vibrate in a similar manner as the first can, thus recreating the sound heard by the second person.

The signal can be directed around corners with the aid of a third can positioned on the apex of the corner. The string is threaded through the base of the third can so as to avoid coming into contact with the object around which the signal is to be directed.

The 600 feet Tin Can Phone A video that could really use some editing, far too long, just skip to the last minute.