Aeronautics Research Mission Directorate 

Screaming String

Suggested Grades: 3-8

Activity Overview

In this activity, you will see how sound waves can be 

focused to increase the volume of a noise. 

Note: For this activity you will be inserting a pin 

through the straws and into an eraser, as well as making 

a hole in the bottom of a cup. You may need to ask an 

adult to help you with this.

Steps

1. Begin by making a small hole in the bottom of the plastic cup as shown in figure 1. If 

needed, ask an adult to help you make the hole.

Figure 1. Make a small hole in the bottom of the cup

2. Feed one end of the piece of string or yarn through the hole in the 

cup as shown in figure 2.

Time: 30 minutes

Materials

• Plastic cup

• 2’-3’ long piece of string or yarn

• Paper clip

• 6”x6” piece of paper towel

• Water

Figure 2. Put the string through the hole in the cup.
3. Tie the end of the string that is outside the cup to the paper clip (see figure 3).

Figure 3. Tie the string to the paper clip.

4. Pull the string the rest of the way through the hole until the paper clip is resting on the 

bottom of the cup as shown in figure 4.

Figure 4. The paper clip should sit on the outside of the bottom of the cup.

5. Fold the paper towel in half twice as shown in figure 5 so it makes a square 

approximately 3”x3”.

Figure 5. Fold the paper towel in half twice.
6. Use water to make the paper towel wet. It should be moist, but not wet enough to drip water.

7. Hold the cup upside down with one hand. With the other hand, wrap the wet paper towel 

around the string as shown in figure 6. Pull down on the string and paper towel while squeezing 

the towel against the string.

Figure 6. Pull the paper towel down while squeezing it.

As you pull the paper towel down, the friction of the paper towel rubbing against the string 

causes the string to vibrate. These vibrations are transferred to the cup. The shape of the cup 

focuses more sound waves in a small area, which increases the loudness.

8. Now, experiment with your screaming string machine. Try applying more or less force while 

pulling the paper towel down. You can also try pulling down at different speeds or pulling 

down a little bit at a time. 
Background Information

What is sound? All sounds are produced by vibrating objects. One of the reasons there are so 

many different sounds is that there is an endless variety of materials that can vibrate and produce 

them. If these vibrations are combined together, it can increase the loudness of the noise being 

created.

X-59 (QueSST) One of NASA’s newest 

experimental aircraft, the X-59 (QueSST) is 

designed to lower the noise created by planes 

flying faster than the speed of sound. When 

planes fly supersonic (faster than the speed of 

sound), the pressure waves they create combine 

together and produce a very loud noise called a 

sonic boom. This noise is so loud that it can 

damage property and disturb animals. 

The unique design of the X-59 is engineered to 

change the movement of the pressure waves so 

they don’t combine and form the loud sonic 

boom. Instead, the plane creates a series of sonic 

thumps which are much quieter than the boom. 

Figure 7. The X-59 (QueSST) is designed to fly supersonic 

without creating a sonic boom.