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ISBN Softcover: 978-1-61930-996-8
ISBN Hardcover: 978-1-61930-993-7
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Timeline. . . iv
Introduction
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Glossary
Metric Conversions
Selected Bibliography
Essential Questions Resources Index
Interested in primary sources? Look for this icon.
Some of the QR codes in this book link to primary sources that offer firsthand information about the topic. Photos are often considered primary sources because a photograph takes a picture at the moment something happens—but watch out for fake ones! Use a smartphone or tablet app to scan the QR code and explore more. You can find a list of the URLs on the Resources page. You can also use the suggested keywords to find other helpful sources. sound
THE SCIENCE OF SOUND TIMELINE
C.* 550 BCE: An ancient Greek named Pythagoras describes the connection between the pitch of a vibrating string and its length.
C. 350 BCE: Ancient Greek thinker Aristotle suggests that sound travels through the air to our ears.
C. 500 CE: Ancient Roman thinker Boethius compares sound waves to ripples of water.
1500: Italian artist and inventor Leonardo da Vinci suggests sound travels in waves.
1635: French philosopher Pierre Gassendi conducts the first experiments on the speed of sound.
1638: Italian thinker Galileo Galilei conducts tests that show the connection between pitch and frequency.
1660: Irish and English physicists Robert Boyle and Robert Hooke show sound must travel through a medium such as air.
1668: English scientist Isaac Newton conducts experiments demonstrating the speed of sound.
1793: Italian scientist Lazzaro Spallanzani is the first person to suggest bats hear sounds that people cannot.
1842: Austrian physicist Christian Doppler describes changes in wave frequency that depend on how a source of waves and an observer move toward or away from each other.
1883: British scientist Francis Galton observes that cats and dogs hear sounds we can’t and invents the ultrasonic whistle.
1876: American inventor Alexander Graham Bell patents the telephone after figuring out how to convert sound waves from human speech into an electrical current and back.
1880: Alexander Graham Bell establishes the Volta Laboratory Association, an electro-acoustic research facility.
*When scholars do not know the exact year of an event, they use the word circa, or its short form c in front of the date. Circa means “about.”
1885: Welsh singer and scientist Megan Watts Hughes invents the eidophone, a device that transforms sound into visual patterns.
1887: Austrian physicist Ernst Mach figures out how to calculate the speed of sound, which is named Mach in his honor.
1895: American anthropologist Alice Cunningham Fletcher records the music of Native American tribes on wax cylinders.
1906: American naval architect Lewis Nixon invents sonar to detect icebergs, and the technology is later used during WWI (1914–1918) to detect submarines.
1925: Scientists, using sonar, detect the Mid-Atlantic Ridge, a massive mountain range in the Atlantic Ocean.
1925: Electric microphones, speakers, and recorders produce and record sound.
1930s: Canadian-American Helen Oakley Dance becomes the first female record producer.
1945: Scientists make sound recordings on magnetic tapes for the first time.
1947: American pilot Chuck Yeager is the first person to break the sound barrier, flying the rocketpowered Bell X-1, an experimental aircraft.
1958: English physician Ian Donald uses ultrasound imaging to look inside the body.
1990: The U.S. Food and Drug Administration approves cochlear implants for children ages 2 to 17.
2016: More than 450,000 people have received cochlear implants worldwide.
2020s: Immersive audio technology means people can listen to performances with headphones and feel as if they’re in the concert space.
WHAT’S IN A
SOUND?
Imagine exploring a wooded park. Squirrels chatter and race over crunchy leaves. Songbirds tweet from leafy branches. Children rush by, clomping their feet, to see the dancing jets of water in the fountain. Burble, burble, whoosh!
ESSENTIAL QUESTION
Why is sound an important part of most people’s lives?
A fountain is a fun place to—SPLASH! Children jump, skip, and stomp while clapping their hands to the beat of their feet and joining in the symphony of sounds. Maybe someone brought a harmonica to the park— what kinds of sounds does it make? Do you hear the hum of conversations happening among the people around you? Listen to the rolling skateboards, zipping bikes, and pounding sneakers. How many sounds can you hear?
THE SCIENCE OF SOUND
WORDS TO KNOW
symphony: a piece of music written for an orchestra.
sound: vibrations that travel through matter, which is any substance that has mass and takes up space, such as air, water, and wood.
orchestra: a group of musicians that play a variety of instruments.
soothe: to make someone feel calm. energy: the power to work and move.
solar energy: energy from the sun.
livestock: animals raised for food and other uses.
photosynthesis: the process plants use to convert the sun’s energy into food.
chemical reaction: a process where one or more substances are chemically changed and transformed into different substances.
nuclear reaction: when atoms fuse together or split apart. This releases a large amount of energy.
SOUND IS ALL AROUND YOU
For many people, the world is an orchestra of sound, from sunup to sundown. When we wake, we hear the buzz of an alarm, footsteps, voices, and the clank of breakfast dishes. During the day, cars honk, desks and chairs squeak, and friends chat and laugh. At night, the fridge hums, water in pipes gurgles, and owls may hoot.
There are many other kinds of sounds, too. Sounds in nature tend to be pleasing. The wind moves leafy tree branches. It makes them rustle. Raindrops pitter and patter onto umbrellas. These sounds soothe. They are beautiful to hear. Animals make an array of sounds, from squeaks and squawks to honks and tiny buzzes. All kinds of creatures use sound to communicate.
How many sounds do you think are happening in this amusement park?
Musicians create sounds with instruments for us to enjoy. They pluck the strings of guitars. Pling! They blow into flutes with a tootleto. Machines produce sounds. They ding, rattle, and bang. People make sounds, too. The average person hears between 20,000 and 30,000 words per day!
Listen to the sounds of the National Parks on this website. How many different sounds can you hear? Do these places sound different from the area around your home?
Now that we have looked at a few sounds, let’s find out exactly what sound is.
ENERGY!
Sound is a type of energy. Energy makes things move and change all around us. The human body needs energy to grow, keep warm, and laugh. Whether we kick a ball, leap into a pool, or play running games at recess, our bodies break down food to release energy for us to play.
Try this! Hold a plastic ruler on the edge of a table. Pluck it with your other hand. When do you hear the sound? Predict what will happen if more of the ruler rests on the table. Pluck the ruler. Was your prediction correct? What happened?
Energy from the sun warms our planet. This is called solar energy. It helps us grow healthy food such as the fruit and vegetables that feed both humans and livestock . Photosynthesis is the process plants use to convert sunlight into the energy they need to grow.
Humans use solar energy in other ways. People collect solar energy with roof panels to create electricity. Millions of homes light up because of this electricity. Energy also comes from the wind and from chemical and nuclear reactions.
National Park sounds
THE SCIENCE OF SOUND
WORDS TO KNOW
vibrate: when an object shakes up and down or back and forth.
phenomenon: something seen or observed. Plural is phenomena.
conductive: describes a material that carries electricity easily.
attract: when an invisible force pulls things together.
force: a push or pull that changes an object’s motion.
matter: any substance that has mass and takes up space, such as air, water, and wood.
atom: the tiniest building block of matter.
molecule: the smallest amount of something.
technology: tools, methods, and systems used to solve a problem or do work.
microscope: a tool that helps scientists look at objects invisible to the bare eye.
All sounds, from the chirp of insects to the meow of a cat, begin with energy. A door doesn’t make a sound on its own. Your hand needs to move it. When you pull the door open, it vibrates and your ears hear a creak. When you push it shut, the door vibrates again and your ears hear a firm click. Sometimes, the sound from a door might begin with energy from the wind. The door closes with a bang when the wind whisks it shut. The energy from the door creates a back-and-forth or up-and-down movement called a vibration, which travels through the air to our ears, where we hear it as sound.
Let’s find out how the sound vibrations travel to your ears.
Underwater Sounds
Long ago, people didn’t know if sound traveled in liquid. So, French scientist and priest Jean-Antoine Nollet (1700-1790) conducted sound experiments in a river. He discovered he could hear sounds, including a bell, underwater.
Nollet was also interested in electricity and did many early experiments to learn more about this phenomenon. He even suspended people from the ceiling using conductive silk rope and electrified them, causing the person to build up a charge and attract things. It’s the same thing that happens when you rub a balloon on your head for a while and then stick it to a wall. But don’t worry, people who helped with Nollet’s experiment weren’t hurt!
MATTER AND MOLECULES
Sound travels from a source such as a bell, a band, or a waterfall to the ear through matter. Matter is everywhere. Just about everything we see is made of matter. Your chair, the table, this book, your wornin shoes and a favorite soft blanket—all of this is matter. It’s everything we touch. You are made of matter, too!
Learn more about how sound travels underwater in this video. Why do you have more trouble understanding your friend’s words underwater than on land?
Discovery sound travels
Matter is made up of teeny building blocks called atoms. When atoms join with one or more atoms, they form larger particles called molecules. A molecule of water, for example, is made of two hydrogen atoms and one oxygen atom. Molecules are much too small for humans to see without advanced technology. They can’t be seen even with a regular microscope.
What isn’t made of matter? Your thoughts and emotions—can you weigh or touch them? No! Can you weigh or measure light? No! These things aren’t made of matter. Can you think of others?
The bow makes the strings on this cello vibrate, and that vibration produces sound.
THE SCIENCE OF SOUND
WORDS TO KNOW
sound wave: an invisible vibration in the air that you hear as sound.
state of matter: the form that matter takes. The four states of matter are solid, liquid, gas, and plasma.
solid: a state of matter with a definite shape.
liquid: a state of matter that takes the form of its container and has a fixed volume volume: the amount of space an object takes up.
gas: a state of matter in which atoms and molecules are spread far apart.
plasma: a state of matter similar to a gas but with temperatures and pressures so high that electrons are stripped away from their atoms and move freely. It is the most common form of matter in the universe.
wave: a curving movement in water, air, ground, or other object.
climate change: a change in long-term weather patterns, which can happen through natural or manmade processes.
stethoscope: a tool used by doctors to listen to sounds inside the body.
How tiny are they? A single molecule is 10 trillion times smaller than a single grain of rice!
How do the molecules in sound begin moving? Something must vibrate to get them moving. Imagine yourself plucking the strings of a guitar. Twang! The strings vibrate each time you pluck them. The strings’ vibrations kick off a reaction similar to bumper cars—the molecules bump into the ones next to them, causing them to vibrate.
The vibrating molecules create a sound wave that carries the sound from the object to the ear. We’ll learn more about sound waves in Chapter 1.
THREE STATES
There are four states of matter solid , liquid , gas , and plasma . An ice cube is a solid substance until it melts and becomes a liquid. As time passes, some of the liquid water will turn to gas in a process called evaporation. Much of the sun is made of plasma. Lightning strikes create plasma, too!
Sound travels more easily when the molecules in the matter it’s traveling through are closer together. That means sound travels quickly through a solid, less quickly through a liquid, and slowest through a gas.
To model a solid, imagine a group of people standing in a marching band, locking arms so they are all stuck together. There’s not a lot of room to move and vibrate, so sound waves will slip through without using a lot of energy.
A model of a liquid is like a very crowded room. People are moving around, but they are still practically touching each other. There’s more room between them than there was when they were a solid, but sound waves still travel pretty easily through the crowd.
Learn more about sound with this video. How can you show that sound travels in waves?
In a gas, people have a lot more room to move. A person can spin their way across the room without bumping into too many other people. That means sound waves have to work harder to make the leap from molecule to molecule. Those waves are going to move a lot more slowly.
What would it be like to listen through a wall?
Rest an ear on a wall and tap on it. What do you notice?
In this book, you’ll explore the loudest sounds in history. We’ll also talk about the quietest areas on Earth. One place is so quiet, people can hear their eyeballs squelching in their heads!
You’ll also discover how scientists use sound to explore the ocean, look inside the body, and study climate change. Plus, make some career connections in the field of sound. Along the way, you’ll turn glasses into a musical instrument, a bowl into your eardrum, and a tube into a stethoscope. Ready? Let’s go catch some sound waves!
Essential Questions
Each chapter of this book begins with an essential question to help guide your exploration of sound. Keep the question in your mind as you read the chapter. At the end of each chapter, use your science notebook (you’ll make that next!) to record your thoughts and answers.
ESSENTIAL QUESTION
Why is sound an important part of most people’s lives?
MAKE A SCIENCE NOTEBOOK
For scientists and engineers, notebooks are very important tools. That’s where they write down their observations and record their data. It’s also where they keep track of their experiments, often by using the scientific method (which you’ll learn about on page 10). Make your own science notebook to use as you do the experiments in this book!
› Cover the notebook front and back with the patterned paper and cardstock and secure with glue. Set to one side.
› From the plain paper, cut out a label roughly one-third the size of the notebook. Write your name on the label and add any details and drawings you’d like with your colored pencils and washi tape.
› Cut the ribbon long enough to wrap around your notebook. Glue the ribbon down across the front and back of the notebook so it can be tied closed at the opening edge.
Try This!
TOOL KIT
• a composition notebook
• assorted patterned paper and cardstock
• scissors
• glue
• 1 sheet of plain paper
• colored pencils
• washi tape (optional)
• ribbon
• pencil
Italian artist and inventor Leonardo da Vinci (1452–1519) was known as a visionary. He did many experiments and built many models trying to understand the world. And he kept many notebooks! Take a look at Leonardo’s notebook on this website. How is it different seeing his writing and drawings as opposed to reading them typed out? Do you learn something different?
Leonardo da Vinci kept his notebooks safe even as he worked and traveled throughout Europe. How can your notebook be kept safe during your sound investigations?
TEXT TO WORLD
What are some ways you protect yourself from noises that are too loud? How about sounds that never seem to stop? How do you control the sounds you hear?
Leonardo da Vinci notebook
COLLECT SOUNDS
TOOL KIT
• science notebook and pencil
• recording device
A laugh and a sneeze. Achoo! A song on the radio and the ding of the doorbell. Sounds surround us. It’s important to be aware of the sounds around you, as they can give you clues about what’s going on in your environment. How many sounds can you collect in this activity?
› Explore your home when it is quiet. Write down every sound you hear in your science notebook.
› Write down two adjectives describing the sound. Some examples include loud, ferocious, whispery, hollow, stuttering, smooth, and constant.
› Use one of the adjectives in a sentence to describe the sound.
› Record the sound. You will use these recordings in the next activity.
THINK MORE!
The Kelso Dunes in the Mojave Desert in California make a unique sound. Watch this video to learn more about these singing dunes! Do you have anything like this where you live? How can you show that sound travels in waves?
Your ears send sound signals to your brain. Then, your brain tells you what the sound is. How do you think these signals travel? Learn more about this process in Chapter 2.
Try This!
Make a list of five human noises, such as laughing, in your science notebook. How do the sounds we make help us understand each other?
Nat Geo singing dunes
WHAT’S THAT SOUND?
TOOL KIT
• science notebook and pencil
• recording device
You’ve studied the sounds around you and recorded some of them. Now, it’s time to play a game with these sounds. Can you tell the sounds apart?
This activity is done with a partner.
› Ask your partner to sit quietly.
› Play one sound at a time from the recordings you made in the last activity.
› Can your partner guess the sound?
› After your partner has correctly identified three sounds, switch places and repeat the experiment.
The Scientific Method
A scientific method worksheet is a useful tool for keeping your ideas and observations organized. The scientific method is the process scientists use to ask and answer questions. Use your science notebook to make a scientific method worksheet for each experiment you do.
Try This!
Could you tell which object each sound belonged to? What sounds could you identify more easily? Did you both identify the same sounds?
Question: What are we trying to find out? What problem are we trying to solve?
Research: What is already known about this topic?
Hypothesis: What do we think the answer will be?
Equipment: What supplies are we using?
Method: What procedure are we following?
Results: What happened and why?
SOUND DETECTIVE
Each outdoor space has unique sounds. How many sounds can you collect outside? It’s time to become a sound detective!
› Take a listening walk near your home.
› Stand as still as possible. When you hear a sound in the environment, listen to it carefully. Ask yourself where is it coming from and what is making it.
› Walk on until you hear your next sound and repeat step two.
› After your sound walk, use colored pencils to draw pictures of what made each sound in your science notebook. You can also write a paragraph describing each sound. How are the sounds you heard different from each other? Are any of them similar?
Try This!
How do the outdoor sounds compare to indoor sounds? What are some reasons for these differences?
TOOL KIT
• science notebook and pencil
• colored pencils
Listen to sounds from around the world on this website. With permission from an adult, submit a sound from where you live. What are some of the differences between places that you notice?
sound cities
SEEING MOLECULES
Atoms make up everything in the world. When atoms form bonds, they create molecules. Molecules are too small for you to see with your eyes, but you can build models of them.
TOOL KIT
• science notebook and pencil
• bag of mini marshmallows
• package of toothpicks
• sticky notes
• colored pencils
› Look at the diagram of a water molecule on this page. Use the mini marshmallows and toothpicks to recreate this model. The marshmallows represent the atoms, and the toothpicks represent the bonds between the atoms. Make as many models as your supplies allow.
The word “sound” comes from the old French word son, which means “sound” or “note.”
› Create the three states of water on a flat surface by dividing the models up to represent water molecules in a gas, a liquid, and a solid. Water is different from other substances. In its solid form, the hydrogen atoms of one molecule stick to the oxygen atoms of another molecule and make a three-dimensional structure of ice. This makes ice less dense than the liquid form of water. That’s why ice cubes float!
› Which model represents a solid, a liquid, and a gas? Write your answer in your science notebook and explain why.
› Using the sticky notes, label the models “water vapor,” “liquid water,” and “ice.”
› Add diagrams to your science notebook.
Try This!
Make a marshmallow model for a different molecule.
