Q&A for How to Make a Play Telephone

Pull the string tighter. Often, we can't hear the sound because the string is too loose.

Yarn has a lot of loose threads that works as a vibration dampener. A taut string will carry the vibration much more cleanly.

Nope, cups of any size should work equally well.

Because the noise is from the string vibrating and when it is tight allows it to travel through better.

A foam cup or paper cup will work well. Tin cans have been used to make this for decades, so it works well too.

Have each listener pull on an end, so that it doesn't sag in the middle between the two cups/cans. They must be the right distance between each other.

No, wire is too thick. If you wanted to use wire, you would have to split it in two.

Yes, a piece of thread should work just as well.

The primary reason is that the foam works as a megaphone for your ears - the sound has increasingly more space to move around before it reaches your ears.

Take a screwdriver or tack and poke a hole into a tin can.

The length is decided by the type and quality of your string. You can make it as long as the string allows, by testing it. Hold the string tight from two sides -- get someone to help you. If you see that from a certain point it loosens up too much and you can't tighten it as much as you try, then that's where to stop.

The purpose depends on who is using it. It can be educational, or a way to have fun. It could be both: a fun way to learn how sound travels.

Of course, as long as the other house is close to yours. If you get too far away, it will be much harder to tighten the string, so it will loosen up and lose most or all of the sound.

Yes you can, since it's a type of string. If you're positive that it won't break, it's fine. There shouldn't be any problem in using dental floss instead of string.

Anything that vibrates easily and is long can be used, but it won't be flexible and can't be stored easily.

You could try it! From my personal experience, tin cans work best to make a play telephone.

It is possible to tie another cup to the main string. Just remember to make the knot small, or it may interrupt the entire line.

You need about 2 feet of string, two cups and a push pin.

Any length should work, as long as the string is tight and nothing else is touching the string.

No. If you are far away, the string should be tight, though.

Then you and the person on the other end will be very close to each other.

Yes, but you'll need to be very careful since the edges might be sharp.

When you talk into the cup or can, vibrations go through the air. These are known as sound waves. The vibrations travel through the string and then go out the other cup. The ear interprets these vibrations as sound.

Tin cans, as the metal will conduct and amplify the sound better than plastic.

Both are fine, depending on the distance. Think about which one is thicker and heavier. You don't want a thin piece of thread that will break easily or get blown away by the wind. If you plan to use thread within the house, it should be fine.

Absolutely nothing will happen, as long as the knot is tight. If the knot is loose, it probably means your string is loose and that's going to interfere with the sound transmission.

Yes. Any type of bowl-shaped cup will work. However, metal will work better than non-metal.

It doesn't matter, but sound will travel better over shorter distances.

Yes, you can make whatever type of play phone you would like.

The world record is 300 meters; however, the sound was very poor. People say that the highest you can use for clear sound is 30 meters. You can go well above this limit, but beware that the sound will be very poor.