This is one of my favorite homeschool science labs, in part because it asks kids to think hard about something they take for granted: sound. Most kids don’t stop to think about sound, but with this lab, the physics of sound are connected with something tangible that they can see and touch. It’s also easy to do this science at home, there’s nothing you need to buy or store.
This lesson plan accompanies a powerpoint presentation that can be run via the laptop and a computer. The instructor can read the passages as the various pictures come up, or find your own images to use with this homeschool science lab.
Metal spoons (1 for demo, and one for each student in your homeschool science lab group)
Smallish plastic wide-opening containers, like the kinds you get from the deli with salads in them, covered with plastic wrap
A pinch of rice per pair of students
Cookie sheet pans (one per pair)
Toilet paper tube (one per student)
Rubber bands (one per student)
Flashlight (one per pair)
Rubber band (one per student)
Powerpoint presentation found here
READ: Sound is at the heart of everything. From your favorite song to the conversations you have with other homeschool science lab friends.
ASK: But how does sound work? What turns the motions of molecules into the symphonic sounds of orchestras, whistling tea kettles, and barking dogs? (let the kids make suggestions)
READ: Let’s explore the phenomenal world of sound and vibration—and how this natural phenomenon is used for communication and even navigation. Sound good?
SLIDE 1: READ – Sound is an invisible form of energy. Lots of animals can even sense it. Ask your homeschool science lab group for the other senses: (sight, smell, touch). Sound can tell us what’s happening far away, further than we can see—and it’s a powerful form of communication. Think about a lion roaring or someone crying for help. Wolves howl when they are separated from other wolves in their pack. Their long howls can be heard for miles, and they help wolves stay in touch with each other.
Slide 2 (rattlesnake): READ – Sounds are made by vibrations. Some vibrations are easy to see. For example, if you stretch out and twang a rubber band, you can see it moving back and forth. Let’s try it (hand out rubber bands). Do you see the vibrations of the elastic band? Other vibrations are less obvious, but you can feel them. Try putting your hand around your throat and humming a tune. Can you feel the vibrations? Those are your vocal cords moving rapidly back and forth. Without vibrations, the world would be silent. A rattlesnake shakes the end of its tail—making a telltale rattling sound—to warn other creatures not to come any closer.
Slide 3 (sound wave): READ – So how do vibrations travel and get to your ears? The vibrations that create sound must travel through something, a medium, like water or air—or anything made of molecules. And, to fully understand how sound works, we need to remember that air isn’t empty space. Air is actually a fluid, made up of molecules, kind of like the water that fish live in. Although you can’t see air, you can feel the wind, and you can use it to blow bubbles or fill up a balloon. Air can move, flow, and fill up spaces because it is made of invisible gas molecules. The molecules in air are loosely packed, floating and bumping around. It is those air molecules that transmit most sounds.
Hold up a glass and a spoon.
SAY: if you hit a spoon against a drinking glass, it will cause the glass to vibrate. As the glass quickly vibrates, it the glass pushes on the molecules in the air around it, forcing them to move. We can’t see this, because the vibrations are tiny and the molecules are even smaller. Remember how the rubber band moved forwards and backward? The glass is doing the same thing, only MUCH smaller. Everytime the glass moves forward, it pushes air molecules outward and crowding them together. When the glass moves backward, the molecules relax and get less crowded. This happens frequently, creating a chain reaction that travels through the air, and that is called a sound wave.
Point to the sound wave on the slide.
SAY: The blue sine curve on top represents the sound wave, with high points being compressions and low points being rarefactions. The distance from one high point, or compression, to another is called the “wavelength.”
Slide 4 (drum): READ – Sound waves can travel through all kinds of substances, or mediums—some better than others—and that is why sound can travel through solid objects (like a wall or closed window). In fact, most solid materials are better at directly transmitting sound than air. For example, if you take an object, such as a spoon, hold it right in front of your nose and tap the far end very lightly with your finger, you probably won’t hear anything. BUT if you put one end of the spoon next to your ear and tap the other end, a sound wave will travel straight through the spoon and you will hear it clearly.
Let’s try that!
Give each homeschool science lab participant a spoon and let them try!
SAY: Work with a partner. One of you holds the spoon out in front of your nose, keeping it horizontal. The partner should tap the spoon gently with their spoon. How loud is the sound?
Now put the spoon next to your ear and the partner can tap the spoon. Is it much louder? Switch partners so they can try it too.
Drum slide: Hitting the skin of the drum causes it to vibrate and create sound waves. When the sound waves reach your eardrums, they vibrate, too.
Slide 6 (funny guy): READ – Sound waves can’t travel forever. After a while, they lose energy and fade away. They can also be weakened and distorted. When a sound wave traveling through the air encounters an obstacle, such as a tree or wall, some of the energy of the sound wave gets absorbed, so the sound comes out fainter and sometimes garbled on the other side.
Can you hear what’s going on in the next room by putting a glass to the wall and pressing your ear against it? Yes, this trick really does work. The sounds in the next room are transmitted through sound waves into the wall, which absorbs most of the vibrations. The glass can help you pick up the vibrations directly from the wall and amplify them straight into your ear. You can’t hear perfectly, but you hear more. Give your homeschool science lab group a chance to explore this phenomenon.
Slide 7 (space): ASK – where can’t you hear sounds? That’s right, in outer space! Does anyone know why? In outer space. Sound waves require a medium to travel through. Outer space is a vacuum, and therefore it is silent. However, you can hear inside spacecraft if air is pumped in.
Slide 8 (lightning): READ – Sound waves travel through different mediums at different speeds. At sea level, sound waves travel through the air at about 760 mph—about five miles a second—which means you can hear nearby sounds almost instantaneously. But they move through water 4 times that fast and through steel more than 17 times as fast.
ASK: Why do you see lightning before you hear its thunder?
Light travels much faster than sound. The sound of a thunderclap is caused by the lightning heating air molecules and pushing them outward, setting up an enormous sound wave.
Slide 9 (plane): READ: When an object moves at the speed of sound, it is said to be traveling at Mach 1. When a jet surpasses the speed of sound, it “breaks the sound barrier” and causes a sonic boom—which sounds like a clap of thunder. When it’s humid, jets form a vapor cone as they break the sound barrier.
Slide 10 (ear): READ: Sound waves move through the air with astonishing speed. But what happens when they reach your ears? In fact, your ears are so fine-tuned they can process information 1,000 times faster than your eyes.
Sound waves are captured by the outer ear and cause the eardrum (tympanic membrane) to vibrate.
Ears are amazing at catching sound waves. Their curvy shape funnels sound waves into the ear canal (feel free to look up a picture of the ear to show your homeschool science lab group). The sound waves roll into your eardrum—which really is a bit like the skin of a drum. Your eardrum vibrates—and this vibration is sent along a series of connected bones (the hammer, anvil, and stirrup), which are the smallest bones in the human body. The last tiny bone (the stirrup) passes the vibration on to a membrane called the oval window. And here’s where things get really interesting. The oval window is the window to the inner ear. When the oval window vibrates, it causes fluid inside the spiral-shaped inner ear (cochlea) to vibrate, too.
Slide 11 (animals) READ: Many animals—horses, rabbits, kangaroos—have muscles that allow them to swivel their ears toward a sound without turning their heads. This is handy when they want to listen for danger. Here’s an interesting fact: Human ears aren’t really built for swiveling, but the muscles are there and some people can wiggle their ears just a little. Can you wiggle your ears?
Slide 12 (microscope) READ: Inside the inner ear, the microscopic tips of hair cells look (kind of) like bunches of hair. Over time, hair cells can get damaged or destroyed by loud noises and other traumas and they won’t grow back. That means permanently losing some—or even all—hearing. But scientists have discovered certain animals (such as chickens) CAN regrow hair cells. This view through a scanning electron microscope shows the hair cells of a chicken blown up thousands of times. Scientists are studying these animals’ ears to see if there is a way to help people re-grow hair cells too.
SAY: So now that we’ve learned all about sound, does anybody want to see what sound looks like?
Hand out the plastic covered containers and foil pan (one per team of two kids) and one spoon. Have parents put a pinch of rice on the plastic.
ASK the homeschool science lab kids to figure out how they can make the rice move on the plastic without touching it with the spoon, foil pan, or hands. (the idea is for the kids to bang the pan right next to the plastic, sending sound waves to make the rice jump).
The rice moves and jumps around because of the sound waves that are caused when the spoon hits the pan. These sound waves travel through the air and when they reach the plastic wrap it vibrates causing the rice to move. The sound waves are also what allow us to hear the noise of the spoon hitting the pan.
Set up for the final lab (this concept is the same but there’s more wow factor – this is perfect for homeschool science days!)
Hand out the toilet paper rolls covered with plastic.
Tell the kids what to do when the lights go out: In a darkened room, hold the open end of the tube in front of your mouth, with the covered end pointing at a wall, or smooth surface.
Shine the flashlight on the plastic wrap, so it reflects back to the wall.
Then, talk into tube, and watch as the light reflection on the wall vibrates.
Experiment with your voice. Talk high pitch, talk low, mumble, shriek. You can also clap in front of the tube, ring a bell, or clank spoons together. The kids should be able to see the vibrations reflected on the wall. There’s lots of WOW factor here!
This lab was inspired in part from a lab by Kids Discover.