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Make Sprinkles Vibrate with Sound

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Summary

Active Time
20-30 minutes
Total Project Time
20-30 minutes
Key Concepts
Sound, vibration
Credits
Ben Finio, PhD, Science Buddies
Vibration & Sound: Make Sprinkles Dance

Introduction

You might know that sound is caused by vibrations, but did you know that sound can also make things vibrate? You might have noticed this if you have ever been at a concert or in a car with the stereo booming. Sometimes the sounds are so loud that you can feel the vibrations! However, sounds that loud can damage your hearing, so in this project you will investigate them using something safer.

This activity is not recommended for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Materials

  • Cup or bowl
  • Rubber band that fits around the cup or bowl
  • Plastic wrap
  • Colored sprinkles (you can also use salt, but the sprinkles are easier to see)
  • Large plate or tray

Prep Work

  1. Stretch a piece of plastic wrap across the top of the bowl.
  2. Use a rubber band to hold the plastic wrap in place.
  3. Adjust the plastic wrap so it is tight and as flat as possible with no wrinkles.
  4. Put the bowl onto a plate or tray to catch any sprinkles that fall off.

Instructions

  1. Bring your lips very close to the edge of the bowl without touching it.
  2. Try humming loudly, and watch the plastic wrap closely.
    Think about:
    What happens? Can you see anything?
  3. Add some sprinkles to the top of the plastic wrap.
  4. Try humming again. Watch the sprinkles closely.
  5. If nothing happens, try humming louder
  6. If nothing happens, try varying the pitch of your humming (higher or lower).
  7. If the sprinkles fall off the bowl, add more of them as needed.
    Think about:
    What happens when you stop humming?

What Happened?

Did you make the sprinkles dance? When you hummed loudly enough and at the right pitch, the sound waves generated by your voice should have made the plastic wrap membrane vibrate. The vibrations of the clear plastic wrap are hard to see on their own. When you add sprinkles, the vibrating membrane makes them bounce up and down, so the vibrations are much easier to see. For a more detailed explanation of the physics behind this project, see the Digging Deeper section.

Digging Deeper

Have you ever heard the age-old riddle "if a tree falls in a forest, and there is no one there to hear it, does it make a noise?" If you know how sound waves work, then the answer is pretty simple. Sound waves are created by vibrating objects that bump into adjacent air molecules. These air molecules bump into other nearby air molecules, and so on, transmitting the vibration through the air to our ears. Sometimes these vibrations are easy to see (e.g. when you pluck a rubber band), but most times the vibrations are too small or too fast for us to see (e.g. when you knock on a door, it makes a sound, even though you cannot see the door vibrate). In the case of the falling tree, the tree will still cause vibrations when it hits the ground, even if there is no one there to hear it.

So if vibrations cause sounds, can sounds also cause vibrations? It turns out that it works both ways, and this is what allows us to hear. You have probably heard of your eardrums, tiny membranes inside your ears (maybe an adult told you not to poke anything tiny or sharp into your ears, because you could damage them). When vibrating air molecules hit the membrane, they cause it to vibrate. These vibrations are converted into electrical signals that are sent to your brain.

In this activity, you made a membrane that behaved similarly to your eardrum. Depending on the size, shape, and material of the container you used, you might have had to adjust the pitch of your humming to get the sprinkles to dance. If your pitch was too high or too low, the sprinkles might not have moved at all. If you got the pitch just right, the sprinkles might have bounced around like crazy and even fallen off the bowl. The way an object responds to sounds of different pitch is called its frequency response. Frequency is measured in hertz (Hz), or the number of sound waves per second. Human hearing typically has a range from around 20 Hz to 20,000 Hz, meaning frequencies in that range will cause your ear drum to vibrate. Some animals, like dogs, can hear much higher frequencies, up to around 45,000 Hz. That means that unlike humans, their ear drums are sensitive to vibrations at higher frequencies. That is why dogs can hear "dog whistles" but we cannot!

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For Further Exploration

  • Try the activity with different-sized granular materials. For example, what happens if you use tiny spherical sprinkles vs. bigger oblong sprinkles or "jimmies"? What about salt or grains of rice?
  • Try the activity with containers in different sizes, shapes, and materials.
  • Try putting the bowl in front of a speaker and playing music.
  • Search for a "tone generator" app or website on your phone, and try playing a constant tone near the bowl. Some tones can hurt your ears, so start with the volume very low and increase it gradually.

Lesson Plans

    Lesson Plan Grade: 1st
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    2 reviews
    Young students know that they can hear sounds, but do they know what causes sounds? In this lesson they will learn that sounds are caused by vibrations, and they will build a fun musical instrument of their own. In the Sound and Vibrations 2: Make Sprinkles Dance, students will learn that sounds can also cause vibrations. Read more
    NGSS Performance Expectations:
    • 1-PS4-1. Plan and conduct investigations to provide evidence that vibrating materials can make sound and that sound can make materials vibrate.
    Lesson Plan Grade: 1st
    Can you make something move by using only sound? Your students will find out in this lesson plan as they explore the connection between sound and vibrations. This is the second in a pair of lessons about sound. See Sound and Vibrations 1: Rubber Band Guitar for the first lesson. Read more
    NGSS Performance Expectations:
    • 1-PS4-1. Plan and conduct investigations to provide evidence that vibrating materials can make sound and that sound can make materials vibrate.

Careers

Career Profile
On each side of your head is the auditory system, one of the most beautifully designed organs in the human body. The auditory system not only detects sound, but is closely tied to the vestibular system, which helps a person with balance, and knowing how his or her body is moving through space. Audiologists detect, diagnose, and develop treatment plans for people of all ages who have problems with hearing, balance, or spatial positioning. This important work impacts how well a person is able to… Read more
Career Profile
Physicists have a big goal in mind—to understand the nature of the entire universe and everything in it! To reach that goal, they observe and measure natural events seen on Earth and in the universe, and then develop theories, using mathematics, to explain why those phenomena occur. Physicists take on the challenge of explaining events that happen on the grandest scale imaginable to those that happen at the level of the smallest atomic particles. Their theories are then applied to… Read more

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