Listen Up: Your paper towel roll has musical talents!

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Showing sound amplification to kids is as easy as saving a used paper towel tube and a couple of plastic cups.

This experiment shows kids all about sound amplification by focusing sound waves and resonating. There is also a hidden lesson on sound vibrations, by feeling the cardboard tube as the sound projects. It’s a simple experiment on sound science!

Let’s rock and roll!

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How to make the Listen Up tube speaker experiment

Supplies you will need

For this experiment, you’ll need:

• Paper towel cardboard tube
• Plastic cups (2)
• Scissors or craft knife
• Play-Doh or modeling clay
• Smartphone
• Optional: markers and stickers

Before you start

The plastic cups will cut very easily and could rip the cup, so go slowly when making your circles in them!

Instructions

Here is how to do this experiment with your child:

Step 1 (optional): Decorate your paper towel tube

If you want to decorate your speakers, now is the time to do it! You can use markers, stickers, or anything really to make your speakers as festive as possible.

Step 2: Cut a hole the size of the paper towel tube in each cup

Hold your paper towel tube against the side of one of the plastic cups and draw a circle on the cup. Repeat for the second cup.

Make sure that the circle is in the same area on both cups so they will sit evenly when you put the speaker together.

Using a pair of scissors or a craft knife, carefully cut out the circles on each cup.

Step 3: Carefully place tube into cups

Be careful when placing the tube inside of the holes you created in the cups, since the cups can easily rip.

If you’re struggling to fit the tube in, make minor adjustments in the circles you cut out until it fits comfortably.

Step 4: Use Play-Doh or modeling clay to create an air-tight seal on cups

Place the cardboard tube into each of the holes you cut out in the cups and secure it in place with Play-Doh or modeling clay. Be sure that the cups are facing the same direction as one another.

The Play-Doh or modeling clay seal should be as airtight as possible.

Step 5: Cut small slit in cardboard tube for smartphone

Place your speaker down so the cups are resting on their sides. Use your craft knife or scissors to cut a small slit in the cardboard tube at the top.

The slit should be about the size of your smartphone so it can fit inside of the tube, but not much bigger than that.

Step 6: Turn on the music!

Place your smartphone inside of the slit in the cardboard tube, turn on some music, and jam out!

The STEM behind the Listen Up tube speaker experiment

This experiment teaches:

• Sound amplification
• Vibration = sound
• Repurposing things

How it works

Transforming a paper towel roll into a speaker is all about sound amplification through resonance.

The roll acts as an enclosure, channeling sound waves from your phone outward. The cups act as a resonator, amplifying specific frequencies.

While not high-fidelity, it’s a neat way to experience how basic materials can influence sound!

Sound amplification

In our experiment, the paper towel roll can amplify sound in two main ways: focusing the sound waves and resonating.

Imagine sound waves like ripples in a pond. Normally, they spread out in all directions, losing energy as they travel.

The paper towel roll acts like a funnel, channeling the sound waves in a narrower direction. This concentration of sound energy makes it appear louder to the listener in front of the “speaker.” Think of cupping your hands around your mouth to speak – it works on the same principle.

The sound can also be amplified by something called resonance, where the vibrations reinforce each other, making the sound louder. The air inside the paper towel roll vibrates along with the sound waves entering it. 

The size and shape of the paper towel roll affect the resonant frequency, meaning specific sound frequencies get amplified more than others. This can sometimes change the sound quality slightly.

Vibration = sound

Sound originates at a point from a strum, tap, or disturbance, which causes a vibration to travel through the air. Our ears detect that vibration through changes in pressure, whether it’s more pressure or less pressure in the air.

Those fluctuations in pressure make up a vibration, and our ears interpret that vibration as sound.

As we get farther and farther from the source of the vibration, the intensity of the sound drops rapidly.

Repurposing things

This experiment allows you to talk to your child about using everyday items for different things. It’s recycling at its best!

Repurposing old items or even something you might ordinarily throw away shows kids that the life of an item doesn’t stop once we’re done using it. It can be used for lots of things! In our experiment, we are taking what most people throw in the trash or recycling (a paper towel roll) and using it to amplify the speakers in our smartphones.

What else can you repurpose?

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More experiments about sound to try out with your child

• Ringing Spoons: Changing the frequency of sound vibrations using just yarn and spoons
• Dancing Rice: See sound vibrations in action!