FOCUS: Sound is what we hear when something is vibrating. The vibrating object – whether a violin string, a singing bird, or a gurgling brook – creates a sound wave that travels to our ears, where we interpret its meaning. Sound waves need a medium like air, water, or a solid through which to move; they cannot pass through a vacuum. The Earth’s atmosphere, hydrosphere, and geosphere provide a way for sounds to travel. Many animals depend on sound to learn about their surroundings and to communicate with others of their kind.
Objective: To begin to explore and ask questions about sound.
Ask children to put their hands on their own throats as they make a noise like a frog and sing like a bird. What do they notice? Next, ask all children to make a “shush” sound. Do they notice a difference?
PUPPET SHOW “Calls of the Wild”
Objective: To learn how different animals hear and make sounds, and how sounds are important in their lives.
Perform the puppet show, or have a group of children perform it for the class. Afterward, ask questions to review the key details and vocabulary in the story. How was sound important to the different animals in the puppet show? (Chickadee – contact calls, listening for danger; woodpecker – finding food, advertising territory; jay – alarm, warning others; hare – knowing the weather, knowing where he is, listening for predators.) What are some other ways that sound is important in our lives or those of animals? (Calling for help, young begging for food, crossing roads, enjoying music, speaking, etc.)
Materials: puppets, script, stage, three signs for audience participation.
PAINT STICK ORCHESTRA
Objective: To investigate what is happening when something makes a sound.
Give each child or pair of children a paint stick. Have one child place the stick flat on a table or bench, so that about two thirds of it extends out beyond the edge. Have the child hold the stick firmly, pressing down on it with the heel of one or both hands. Have the other child pluck the free end of the stick so that it vibrates up and down. Does it make a sound? What about when it stops moving? (The sound stops.) Have everyone sing a note and feel their throats to feel the vibrating vocal chords. If available, play a guitar string, drum or cymbal to show how it vibrates when making a sound. What is happening when something makes a sound? (It is vibrating.) Have them experiment with making the stick shorter (less of it extending beyond the table edge) and longer (more of the stick extending beyond the table edge). How does the sound change? (Longer is slower and sounds lower.)
Optional: Have the children “play” paint sticks as you conduct them. Conduct them to play faster and slower, louder and softer, as you wave your arms, and then to stop when you stop.
Materials: wooden paint sticks, one for each child or pair of children; optional: guitar, drum, cymbal or other instruments.
PLAYING WITH PITCH
Objective: To investigate the connection between length of a vibrating object and its pitch.
Provide a set of three or four tuning forks in different lengths. Instruct the children on the correct way of using the striker, and how to amplify the sound by holding the stem of the tuning fork upright on a wooden box or wooden table. Have them look closely at the tuning fork to see if any vibration is apparent. They may want to touch the tines to feel the vibrations. Place a dish of water on the table. Have the children try striking the tuning fork and then touching the water. What happens and why? (The vibrations make the water move.)
Now give each child a different length of tuning fork to play. Ask children if they remember whether the sound got lower or higher when they made the paint sticks longer. What is their prediction about the pitches of the different sizes? Have them try a couple of different lengths to test their ideas. Then have them line up in order of size and strike their tuning forks one by one. How is length related to pitch? (Longer is lower, shorter is higher.) What are some low sounds in nature? (Mooing, growls, lion’s roar, bullfrog, rock slides.) High sounds? (Birdsong, spring peepers.)
Materials: set of three or four tuning forks in different lengths, rubber striker, wooden box or wooden table, dish of water.
Objective: To investigate the connection between length or mass of a vibrating object and its pitch.
Use three or four similar-sized bottles filled with different amounts of water. Tap each bottle to compare the sound. Line them up from lowest to highest. Which has the lowest pitch? (The one with the most water.) Which has the highest pitch? (The one with the least water.) Why the difference? When you tap the bottles, it is the bottle that is vibrating. The heavier, fuller bottle makes the lower, slower vibration.
Materials: three to four similar-sized, narrow-necked glass bottles, water, spoon to tap bottles.
COAT HANGER CHIMES
Objective: To use a model to compare how well sound travels through a solid or a gas.
Ahead of time, tie two two-foot long pieces of string to each coat hanger. Hold up a coat hanger by the strings and tap it with a metal spoon. Ask the children to describe the sound they hear. Remind them that the sound wave is traveling through the air to their ears. Now have children take turns wrapping the string around their fingers and then putting their fingers to their ears. Have the child lean forward so the hanger is not touching any clothing. Now tap the hanger with the spoon again. Ask the child with the hanger to describe the sound now. (Loud, bell-like.) Why is it louder? Point out that the sound wave is traveling through the hanger and the string to the bones of their face and then to their ear – so it is moving through a solid instead of through air. Try again using a cookie rack. Do sounds travel better in solids than in air? (Yes) Why? (The particles – molecules – of a solid are closer together.)
Materials: for each small group: metal coat hanger, string, metal spoon, cookie rack.
Objective: To model and compare how fast sound travels through a solid and a gas.
How fast do sound waves travel in different kinds of materials, such as a gas like air or a solid like metal? In a gas the molecules are far apart and in a solid they are tightly bonded together. Have children form two parallel lines. The children will pass a sound along by tapping hands or (gently) tapping the shoulder of the next child in line. The child at the far end of the line should say “here” when the “sound wave” arrives. Have the children in the Air line spread out so they are about 6 feet apart. Have the children in the Metal line stand shoulder to shoulder. Have a leader say “go” to start the sound wave. Which wave arrives first? Does a sound wave travel faster through a gas or a solid? (Solid.) Why? (The molecules are closer together.)
EARDRUMS IN ACTION
Objective: To use a model to investigate how sound waves make our eardrums vibrate.
Have children work in small groups with an adult. Place an empty coffee can on a table with a piece of plastic wrap stretched taut over the open end, held in place by a rubber band. Sprinkle some colored sugar crystals on the plastic. Explain that our eardrums are like the plastic, a thin membrane stretched across our ear canal. Now make a short loud sound above the plastic by hitting the small soup can with a metal spoon. Watch the sugar crystals jump when you hit the small soup can. What makes them jump? (Sound waves from the soup can hit the plastic and make it vibrate.) Repeat using a tuning fork to make sound waves. Try holding the tuning fork in different positions to see which works best.
Materials: for each group: a coffee can or other large can, one end removed; plastic wrap, rubber band, colored sugar crystals, metal spoon, small soup can; optional: tuning fork.
DOING THE SOUND WAVE
Objective: To model how sound travels through our ears and is interpreted by our brains.
Have the children line up in a row. Show them the Human Ear diagram and describe each of the parts and what it does. Then give each child a Build an Ear card that lists one of the parts of the ear, or tell them which part of the ear they are representing. Keep these in order from the pinna (outer ear) to the cochlea (inner ear) and finally the auditory nerve and brain. Explain that when a sound is made by the leader, the pinna will start a wave (raising and lowering hands), and the other ear parts will continue in turn so that the wave travels from the pinna through all the parts of the ear to the brain. Ahead of time, whisper instructions to the “brain” to interpret the sound that is made when the wave arrives (e.g., if the sound made is “quack,” the brain should say “duck.”) To begin, the leader might say, “woof,” the pinna would start the wave and when it gets to the brain, that child would say “dog barking”. Try (or have a few children try) different sounds (quack, moo, meow, etc.).
Materials: Human Ear diagram; optional: Build an Ear cards.
Objective: to notice and represent on a map the different sounds heard.
Have children work in small groups with an adult. Give each group a map of the school and grounds. Note the time of day and the weather on the map. Tell children they are sound detectives and will be gathering sound evidence, and to do so they’ll need to walk silently and listen carefully. Stop and record sounds in four or five places around the school grounds. You may also do this in four or five places inside the school, such as the principal’s office, the music room, the cafeteria, etc. Keep track of both manmade and natural sounds. Afterward, compare notes with other groups. How many different sounds were identified by the whole class together? What other sounds might you hear at a different time of day, in different weather, or in different seasons?
Optional: Take children to different places around the school and make recordings with a cell phone. Then play these for the other children and have them guess where the recordings were made.
Materials: for each group: clipboard, paper, pencil, map of school and grounds;
optional: cell phones for making recordings.
Objective: To investigate the way sound bounces off large surfaces, comparing different kinds of sounds and distances.
How far and how fast can a sound travel? How could we test this? Bring children to a place where there is a large, flat wall (e.g. side of a building). Explain that they’ll be listening for echoes. Have them stand in a line about thirty feet away from the wall. On the count of three, clap two wooden blocks together to make a loud, sharp sound. Have the children raise their hands if they could hear both the clap sound and an echo. Now move back another thirty feet so that the line is sixty feet away from the wall. Again, have the children listen for the clap and an echo. Is the time between clap and echo greater or less? (Greater.) Why might this be? (The clap produces a sound that travels only the short distance from the blocks to our ears and so it arrives first. The sound wave also travels the distance to the wall and back, so we hear that sound second. The farther we are from the wall, the greater is the space we hear between clap and echo.) Are there returning echoes from other sources? Look around and consider what other features of the landscape might be producing an echo as well. Try long and short, high and low sounds and compare. What kinds of sounds work best?
Materials: two small wooden blocks.
SLINKY WAVES (Grades 3-6)
Objective: To model how a sound wave travels from particle to particle in any medium.
Have two people hold the two ends of a Slinky toy, stretched (slightly) lengthwise on top of a table or bench. Explain that the rings of the slinky are like the particles (molecules) in the air. At one end, have a child squeeze and then release a few of the rings. Watch the wave travel along the slinky, each ring pushing the ring next to it along the slinky. If there is enough force, the wave will reach the end and even return. How is this similar to the way sound moves through the air? (A waving object like the paint stick squeezes the air molecules near it, creating a wave that travels through the air.) How is it different from a sound wave? (In the air, sound waves move outwards in all directions.)
Materials: metal or plastic Slinky™ toy.
UPPER GRADES CHALLENGE: Reading Oscillograms (Grades 5-6)
Objective: To learn how to read oscillograms and use them to distinguish the calls of different owl species.
One way scientists represent sounds visually is to look at the way the amplitude of sound (loudness) changes with time. This kind of graph is called an oscillogram. Begin by showing the students the oscillogram below while they listen to the recording of the spring peeper calling. The call is a series of short peeps, with periods of quiet in between. The oscillogram for this call looks like this:
Each peep looks like a burst of sound signal (loudness) separated by spaces of very low signal (quiet). Now have students listen to the first owl call and look at the four oscillograms on the Reading Oscillograms page. Have students try to match the call to one of the oscillograms. Repeat with the other three owl calls. The adult leader may consult the Reading Oscillograms Answer Key for the correct responses. How might this kind of graph be useful for scientists? (This information, particularly when combined with the frequency (pitch) of the sound, can help distinguish different bird calls, or even individual birds.)
Materials: recording of spring peeper calling, barred owl, great-horned owl, saw-whet owl and eastern screech owl; Reading Oscillograms Sound Files, Reading Oscillograms Answer Key.
JOURNAL ACTIVITY and CLOSING THOUGHTS
Objective: To reflect on sounds that make us happy.
Ask children to write about or draw a picture of a favorite sound. Afterwards, have children share their favorite sounds in small groups or list everyone’s favorite sounds in a large sharing circle.
Materials: science journals or paper and clipboards; pencils, optional: colored pencils.