SOUND
INVESTIGATION # 2
Literature Resources:
SOUND INTRO...
This module provides experiences that help students develop an understanding of how to observe and manipulate sound. They explore these dimensions of the natural world using simple tools and musical instruments.
Students learn that sound comes from vibrating objects. They explore how to change sound volume and pitch, and develop simple models for how sound travels from a source to a receiver.
Throughout the Sound and Light Module, students engage in science and engineering practices by collecting data and designing and using tools to solve problems and answer questions. Students gain experiences that contribute to their understanding of the crosscutting concepts: patterns; cause and effect; and systems and system models.
INVESTIGATION 2 — Changing Sound
Investigation 2: Changing Sound:
Students investigate two systems: the one-string guitar and the xylophone. They confirm that sounds come from objects that are vibrating, and that vibrating objects always make sound. Sound can be stopped by stopping the object’s vibration. The added concept is that sounds can differ in volume over a range from soft to loud. Students find a relationship between the amount of energy used to produce a sound and the volume of the sound. The focus question is How can we make loud and soft sounds?
How Can We Make Loud and Soft Sounds?
Sounds differ in a number of ways, including intensity. The amplitude, or amount of energy in the vibration, determines the intensity of the receptor response, and this translates into volume. From a vibrating object, like a string, gong, reed, or crystal glass, we perceive loud or soft sound.
How hard you strike an object changes the volume of the resulting sound. When you strike a xylophone tube with a mallet using a hard stroke, it will make a loud sound. If you give just a gentle tap to the same xylophone tube, the volume of the sound will be soft. The intensity of the strike (hard or gentle) changes the volume. The greater the amount of back-and-forth motion, the more energy is present. More energy results in a louder sound.
How Can We Make Low-Pitched and High-Pitched Sounds?
Different frequencies (rates) of vibration stimulate different receptors, and in this way we discriminate different pitches of sound. When we play a tune on a musical instrument, we create vibrations that produce pleasing mixtures of sound. Consider the metal bars on a kalimba or tubes of a xylophone. They are identical in every way except length. Striking one after the other, from the longest to the shortest, results in a series of sounds ranging from low to high pitch. A pitch in between high and low is a medium pitch.
Every object, when struck, will vibrate at its characteristic frequency. Generally speaking, small objects vibrate faster than large objects, and the faster something vibrates, the higher the pitch of the sound it produces. High-pitched sounds emanate from high-frequency vibrations, and lowpitched sounds arise from low-frequency vibrations.
When we sit and wait for a guitar player to get her instrument in tune, she is busy creating vibrations. Each time she plucks a string, it starts to vibrate. She uses the tuning knobs on the guitar to adjust the tension of each string. As she increases the tension of a string (makes it tighter), that string vibrates more rapidly, and its pitch goes higher. As she decreases the tension of a string (makes it looser), that string vibrates more slowly, and its pitch goes lower.
Virtually every culture has developed instruments to make sound. Stringed instruments use strings to produce sound by plucking (guitar), bowing (violin), or striking (piano). Wind instruments are essentially hollow tubes fitted with a mouthpiece that produces vibrations. Blowing into the mouthpiece makes the air column inside the tube vibrate. Opening and closing holes along the length of the tube effectively changes the length and shape of the vibrating air column. The result: variation in the pitch of the sound.
Horns, like trombones and trumpets, have mouthpieces that the player blows into with tightly drawn lips—a kind of spitting action. By changing the tension of his lips and the length of the vibrating air column with slides or valves, the horn player can produce a range of vibration rates, changing the pitch.
Percussion instruments operate a little differently. Any resilient object can vibrate if it is whacked. Every object has a natural rate at which it will vibrate when excited. This is its resonant frequency. The resonant frequency of an object is determined by a host of variables, including material and size. Percussion instruments have no vibrating column of air that can be modified, so each sound produced by a percussion instrument requires its own vibrating object. The xylophone is a perfect example. Each note, from high to low, has its own metal or wood bar to hit. That bar always sings out with its one pitch—its one frequency of vibration—predetermined by its physical characteristics.
The size of the instrument is also important. Big instruments generally make lower vibrations than small ones. The smaller the instrument, the faster the vibrations and the higher the sound. Inside a flute, there is a smaller column of air than inside a saxophone. A cello has a bigger body and longer strings than a violin, so a cello makes a deeper sound. Bongo drums make higher sounds than bass drums.
Pythagoras (c. 582–507 BCE), the Greek mathematician and scientist, is credited with first describing the relationship between the length of a vibrating string and the pitch of its sound. Harmony is produced when the lengths of the strings are in simple proportions (like 3 to 2 or 4 to 5).
PART # 1: Changing Volume
- 2. Use the tone generator
Tell students,
We have learned that sound comes from things that are vibrating. Let’s see if we can find out more about sound and how to change sounds.
Close your eyes and listen to these two sounds.
Drop the aluminum-foil ball and then the washer. Ask students how the sounds differ.
Tell them one sound was loud and one was soft. Have them listen to the two sounds again and see which sound is loud and which is soft.
Using the tone generator, select one pitch. Use the volume knob to bring the tone up to a soft sound level; then crank it up to a loud sound. Do it again, and ask students to stand up and use their arms to show which sound is loud and which is soft. Spread your arms out wide to the side for a loud sound, and bring your arms in for a soft sound. A medium sound would be somewhere in between.
Tell students that the word volume means how loud or soft a sound is. Ask students where they have heard the term volume before. They should discuss changing the volume control on the remote for a TV or other device with sound. They may know that larger numbers mean a louder volume and smaller numbers indicate a softer volume. Mute means no sound.
Focus question: How can we make loud and soft sounds?
Introduce the instruments
Tell the class that they have two new sound instruments to explore. Show the equipment briefly, removing one set at a time from its bag.
Explain that a xylophone is a musical instrument made from a set of bars or tubes that make sounds when a mallet hits the tubes. Demonstrate how to lay the tubes on the foam and tap them with the mallet.
Tell students that a one-string guitar is an instrument made with a long string attached to the leg of a desk or table on one side, and then stretched over the table surface and pulled tight with a pencil on the other side. Demonstrate how to set up the string, and insert the plastic cup sitting upside down on the table to make a guitar bridge.
Allow about 8 minutes for pairs of students to explore one of the instruments. Then switch the activities.Ask questions about the xylophone
As students work, ask,
How did you get the xylophone tube to make a sound? [Hit it with the mallet.]
What was the tube doing while it was making a sound? [Vibrating.]
How could you get it to stop making a sound? [Touch the tube.]
How could you get a tube to make a loud sound? [Hit it hard, put more energy into it.]
How could you get a tube to make a soft sound? [Tap it lightly or gently.]
Ask questions about the one-string guitar
- As students work, ask,
How did you get the string to make a sound? [Pulled the string tight and plucked it with a finger.]
What was the string doing while it was making a sound? [Vibrating.]
How could you get it to stop making a sound? [Touch the string.]
How could you get a string to make a loud sound? [Pluck it hard, put more energy into it.]
How could you get a string to make a soft sound? [Pluck it lightly or softly.]
Discuss observations
Ask students to put the materials down and return to the rug. Ask,
What was the object doing when it was making a sound? [Vibrating.]
How did you make a loud sound? [Pluck or hit the instrument hard.]
How did you make a soft sound? [Pluck or hit the instrument gently.]
Review vibration and sound
- Review vibration and sound
Summarize the demonstrations by revisiting these points.
Vibration is a kind of motion. It is a fast back-and-forth motion.
Objects that vibrate make sound. Sound always comes from a sound source (object) that is vibrating.
Sound stops when vibration stops.
Objects can be made to vibrate many different ways, including hitting, plucking, and dropping.
VOCABULARY
gentle
guitar
hard
instrument
volume
xylophone
Science notebooks
How can we make loud and soft sounds?
Have students review the two illustrations on the sheet, showing the xylophone and the one-string guitar. Ask them to answer the focus question in words with a sentence or two. They can also caption and label the illustrations to help with the explanation.
For students who need scaffolding, provide a sentence frame such as, “When I _____, the sound is _____.”
Have students practice forming sentences aloud—one for a loud sound and one for a soft sound—before writing in their notebooks.
Introduce megaphones
- Ask students what they do when there is a soft sound that they want to hear. Students may describe and show what they do:
Move closer to the soft sound source.
Turn their head so their ear is toward the sound.
Cup their hands behind their ears in the direction of the soft sound.
Introduce a megaphone as a way to make the sound louder at the source. The megaphone is also a way to focus the sound and to guide it into the ear (receiver).
Sort loud and soft sounds ...in notebooks
- Distribute a copy of teacher master 11, Sorting Sounds by Volume, to each student. Have them cut the images apart and sort them into loud and soft sounds. Students can glue the images to two pages of their notebook.
Part #2: Changing Pitch
- Review volume
Gather students around the table fiddle and ask,
What is one way sounds are different?
When students say that some sounds are loud and some are soft, turn to the table fiddle and demonstrate how the sound coming from one string can differ in volume. Tell students,
Sounds can be loud, like this [pluck one of the strings with gusto], or they can be soft, like this [pluck the same string gently].
Volume is the word used to describe how loud a sound is. Sirens, jackhammers, trains, and waterfalls make loud sounds. Whispers, leaves falling, buzzing bees, and a pencil writing on paper are soft sounds.
You can also use the tone generator to vary the volume of one tone. You can ask students to review their last notebook entry about making loud and soft sounds.
Introduce pitch
- Pluck two different strings on the table fiddle, one short string and one long string. Try to play them at the same volume. Ask,
How are these two sounds different?
Some sounds are high, like this [pluck the shortest string], and some are low, like this [pluck the longest string]. These two sounds have different pitches. Pitch is the word used to describe how high or low a sound is. Little bells, squeaky doors, sirens, and cat meows are high-pitched sounds. Thunder, jet planes, tuba notes, and the bark of a big dog are low-pitched sounds.
If you have a musical instrument in the classroom, use it to demonstrate more examples of high and low pitch and loud and soft sounds. Ask the class to hum in a high pitch and then in a low pitch; at a loud volume and a soft volume.
Compare two pitches
- Bring out the tone generator and dial up a sound loud enough so everyone in the class can hear it. Keep the volume constant and dial up a low pitch. Use the switch to turn on the sound for a few seconds and then turn it off. Repeat this process with a high pitch.
Ask,
Which tone is higher pitched, the first sound or the second sound?
Repeat this process several times, starting with either a high or low pitch, turning off the tone generator, dialing up a different pitch, and turning it back on. Do this until most students are reporting the pitch correctly. Don’t worry if students can’t hear the difference. They may find it easier to hear the difference when they are using the instruments.
Focus question: How can we make low-pitched and high-pitched sounds?
Describe pitch challenges
- Tell students that they will work in pairs with the two instruments they used earlier, the xylophone and the one-string guitar.
- Monitor the investigation
Your challenge is to find out how to make low-pitched sounds and high-pitched sounds. Once you can compare two sounds, then you can try to compare three sounds, low, medium, and high. Your goal is to be able to tell another person how to make a low sound and high sound before you pluck the string or hit the xylophone tube.
Assign half of the class (eight pairs) to begin with the xylophone; assign the other half of the class (eight pairs) to the one-string guitar.
Give the groups about 8 minutes to work with their instruments before switching. Visit the groups to see how they are doing. Encourage the partners to work together to pluck and hit the instrument and listen to the pitch of the sound.
When students have met the challenges with the first instrument, rotate the materials so they tackle challenges with the other instrument.
VOCABULARY
high-pitched
kalimba
length
low-pitched
medium-pitched
pitch
The highness or lowness of a sound is its ___________. [Pitch.
The loudness or softness of a sound is its ____________. [Volume.]
A musical instrument made from a set of bars or tubes of different lengths is called a __________. [Xylophone.)
Notebook
Distribute a copy of notebook sheet 4, Changing Pitch, to each student and review the focus question. Ask students to write an answer in their notebooks. After they finish, they can glue the sheet in their notebooks.
How can we make low-pitched and high-pitched sounds?
For students who need scaffolding, asking guiding questions such as,
What did you have to do to make the pitch of a sound higher? Lower?
Or provide a sentence frame such as, “You can make a low pitch by ______. You can make a high pitch by ______.”
Part 3: Spoon-Gong Systems
- Review sound
Call students to the rug. Place the metal xylophone tubes on the piece of foam in random order. Play a little tune that uses some of the things students have learned about sound. Ask students to talk with a partner about what they have learned about sound.
Ask the class to help you make a list of the things they know about sound. Write these things on the board.
Sound is made by vibrating objects.
Objects stop making sound when the vibration stops.
The volume of sound may be loud or soft.
The pitch of the sound can be high, low, or medium.
The xylophone tube is the sound source, and our ears are the sound receiver.
Have students come up and demonstrate their point, using the xylophone.
Demonstrate the spoon-gong system
- Hold up a spoon gong. Tell students,
The spoon gong is another way to investigate vibration and sound.
Tell students this system is made up of parts. Have students help you to list the parts of the spoon-gong system (spoon, string, and cup).
Ask,
How can I get the spoon to make a sound? [Drop it, hit it with something to make it vibrate.]
What will the spoon be doing while it is making a sound? [Vibrating.]
How could I get it to stop making sound? [Stop the spoon from vibrating.]
Show students how to hold the cup over one ear and tap the spoon gently with a pencil. Then grab the spoon to stop the vibrations.
Tell students they will each get a spoon-gong system to explore.
Describe the volume challenge
Challenge students to work with their spoon gong to make these observations.
a.Get the spoon to make a soft sound.
b.Listen to the sound.
c.Stop the sound.
d.Repeat, making a loud sound.
Students should work in pairs and help each other use the spoon gong and make sound observations.
Students may need time to practice coordinating the actions of holding the cup to their ear and hitting the spoon.
For some, it might be easier for one person to hold the cup and listen while the other taps the spoon with a pencil.
Students may need a reminder that the spoon should hang free and not touch other things.
Which part of the system is the sound source? Talk to your partner about this question. [The spoon.]
What is the sound receiver? [Students’ ears.
Notebooks
Distribute a copy of notebook sheet 6, Spoon-Gong Systems, to each student. Ask students to talk with a partner about how the pictures are different. [The cup points in different directions.]
Cup pointing toward the receiving ear
Cup pointing up to the ceiling
Cup pointing away from the receiving ear
Tell students they will have a few minutes to try the different cup positions and see how position changes the sound they hear from the spoon gong.
- Draw a model
Ask,
What is the spoon doing when it is making sound? [Vibrating.]
What could we draw to show those vibrations? [Draw lines by the spoon.]
Draw a few curved lines on each side of the spoon to indicate the vibrations. Explain,
I’d like you to take the picture of the spoon gong on your sheet with the cup pointing toward the ear, and draw lines starting like this around the spoon to show the vibrations. Then I want you to draw how the sound vibrations travel to your ear. Talk to your partner about how you would show that.
Have students return to their notebook sheets and draw the lines showing the vibrations.
What you have made is a model. The lines represent what we can’t see, the vibrations.
Ask a student volunteer to come to the board and draw the model, showing how the sound travels from the source to the receiver. As the student draws, ask the class,
Do the vibrations travel through the string? How do you know? [If you pinch the string, the sound stops, so the string must be vibrating.]
View the video: All about Sound
- Tell students that they will see a short video that reviews some ideas they have explored and presents some new ideas. Here is a summary of the video chapters.
Chapter 2, What Is Sound? (2 minutes 38 seconds)
Sound is a form of energy caused by the movement of things.
When something moves, it creates a vibration.
Jumping on a trampoline and tapping a tuning fork are examples of vibration.
Music is a great example of how vibrations make sound.
Chapter 6, Sound: Volume and Echo (3 minutes 54 seconds)
Sound volume can be increased by directing sound into one direction with a megaphone.
A specially shaped microphone aims sound waves to the center of the microphone.
An echo is the result of sound waves bouncing off an object.
Dolphins use sound echoes to tell what is in the water around them.
Bats use sound echoes to find out about the world around them.
Boats use echoes to find objects in the water.
Vocabulary
- Review vocabulary
direction
spoon-gong system
string
system
travel
Answer the focus question
- Ask students to recall the focus question.
How does sound travel from the source to the receiver?
Give them a few minutes to add or revise their models as they feel is needed. Then ask them to write a sentence or two to answer the focus question.
For students who need scaffolding, ask guiding questions such as,
Where does the sound start? Then what happens? Describe what your diagram shows.
Or, provide sentences starters such as “First, _____. Then, _____. Finally, _____.”
For maximum support, provide sentence frames such as, “The sound starts at the _____. The vibrations move to the _____ and then to the _____. The sound is received by the
Part 4: Sound Challenges
Review Sound
We found that it is best to have the cup facing toward our ear to hear the sound when the spoon is hit.
Ask,
How could this student use this spoon gong to send a message to me?
How can I use this spoon gong to send a message to the student?
How can we use it to send messages to each other?
Listen to students’ ideas. They might say such things as, “You can’t get the message because you have the spoon and she has the cup. You don’t get a message with a spoon. And you can only send the message one way.”
Have students build on each other’s ideas and wait for a student to suggest that if you had two cups, you could connect them and hear each other.
Ask,
What can you do to put these two spoon-gong systems together? [Take the spoons off and tie the ends of the string together.]
Make a string-cup telephone
- Tell students that they will work in pairs to connect their two cups. If necessary, demonstrate how to cut off the spoons and use a small piece of masking tape to connect the two strings. Demonstrate how to fold the piece of masking tape around the ends of the two strings and pinch it together.
- The two students should be a short distance apart, facing each other.
- The tension on the string should be tight, not loose.
- The message volume should be a whisper.
- Students need to take turns listening and sending a message.
- Ask students to share what they found out by using the string-cup telephone. They may note that they felt the string vibrating when their partner was talking, and that it didn’t work if the string was hanging loose; it had to be tight.
When each pair has a string telephone, they need to figure out how to send messages to each other. They should whisper messages using words or tap messages using the string or the cup bottom. They should figure out if the string should be loose or tight to send a clear message.
Remind students to take turns sending a message and listening. Allow about 8–10 minutes for student pairs to work on their telephones.
Focus question: How can we use sound to communicate over long distances?
Introduce vocal cords
- Ask students what the sound source was. [Person’s mouth, words, talking.] Ask students to hum, and demonstrate humming for them. Have them gently touch one side of their throat to feel the vibrations of their vocal cords. Tell students that when they talk, their vocal cords vibrate to make sound and the sound is refined by the shape of their mouth and tongue.
ENGINEERING CHALLENGE
- Introduce an engineering challenge
- Start engineering telephones
Tell students they will have an opportunity to make a string telephone from scratch. The challenge is to send a message at least 4 m. You can measure that distance along one wall of the classroom so students have an idea of what that distance is.
Show them the different sizes of cups, and different kinds of string you have provided.
Students can select the materials they would like to use. There are only two guidelines: they must work with a partner, and they need to work safely.
Ask students what they will need to do first. [Make a hole in the cup.]
Show students how to use a pencil to safely poke a hole in the center of the bottom of the cup. If the hole gets too big, it can be repaired with a piece of masking tape.
Students should cut a long string. They can decide the length.
Ask,
How can you attach the string to the cup?
Suggest they look at the previous system they used. Tell them that this is something that engineers do: they look at similar systems and think about how to improve the design.
Show students how to thread the string through the hole and attach a piece of masking tape to hold the string securely in the cup.
Provide assistance as needed. Give students a chance to make mistakes and help them figure out how to move on.
Notebooks
- Draw a diagram of the system
- Share devices and outcomes
- Answer the focus question
When students have completed their designs, ask them to open their notebooks to a blank page, and draw the string-cup telephone, and describe how it works.
Give students a chance to share their designs. Ask them to share some of the problems they had and what they did to overcome them.
Ask students to recall the focus question.
How can we use sound to communicate over long distances?
Give students a couple of minutes to review their diagrams and to write a sentence or two to answer the focus question.
For students who need scaffolding, provide sentence frames such as, “We made a ______. The vibrations start at ______. The sound moves through the ______ and then to the ______. The sound ends up at the ______.”
Vocabulary
communicate
message
Review
What causes sound? [A vibrating object.]
What kind of vibrating object produces a low-pitched sound? [Large.]
What kind of sound does a short vibrating object produce? [High-pitched.]
What does volume mean when talking about sound? [How loud or quiet a sound is.]
Why is sound important in everyday life? [It helps us communicate with other people, warns us of danger, and helps us to know what is going on around us.]
Music Extension
Show and tell about musical instruments
Have student musicians bring their instrument, or pictures of the instrument, to the classroom. Challenge students to figure out what is vibrating when the instrument is sounding.
Make a shaker from toilet paper roll.