Sound physical science

Compare and contrast the ways people and animals make sounds?. Objects that vibrate slowly make a low-pitched sound.. Objects that vibrate quickly make sounds that have a higher pitch..

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by Timothy Sandow

Scott Foresman Science 3.14

Genre Comprehension Skill Text Features Science Content

Nonfi ction Compare and

Contrast

• Captions

• Labels

• Diagram

• Glossary

Sound

ISBN 0-328-13847-9

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Physical Science

Scott Foresman Science 3.14

Genre Comprehension Skill Text Features Science Content

Nonfi ction Compare and

Contrast

• Captions

• Labels

• Diagram

• Glossary

Sound

ISBN 0-328-13847-9

ì<(sk$m)=bdieha< +^-Ä-U-Ä-U

Physical Science

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compression wave

pitch

vibration

What did you learn?

1 How is sound made?

2 Describe the two ways stringed instruments

are played.

3 Explain how your ears help you hear

4 In this book you have read about vocal cords and the pitch of your voice

Write to explain how their relationship works

Use details from the book

make sounds? How do animals make sounds?

Compare and contrast the ways people and animals make sounds

Illustrations: 7, 14 Jeff Mangiat

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ISBN: 0-328-13847-9

protected by Copyright and permission should be obtained from the publisher prior

to any prohibited reproduction, storage in a retrieval system, or transmission in any

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information regarding permissions, write to: Permissions Department, Scott Foresman,

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Sound

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What causes sounds?

Take a walk in the city Cities are noisy Car horns

honk Buses and garbage trucks roar by People talk

on the street It is much quieter in the country Birds

chirp Cows moo Water trickles in a creek

Sounds are everywhere Some sounds you hear may hurt your ears You may like other sounds Each sound you hear is different Sounds are also alike in some ways

Noisemakers are sometimes used on New Year’s Eve

Do you like the sounds they make?

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The Causes of Sound

Sound happens when matter moves back and forth

very quickly This movement is called a vibration

There must be movement to make sound

The instruments pictured make sounds They can

make high sounds They can make low sounds Pitch

is how high or low a sound is Objects that vibrate

slowly make a low-pitched sound Objects that vibrate

quickly make sounds that have a higher pitch

You must hit or shake

a tambourine to make

a sound.

These drums are different shapes

and sizes Each one makes a

sound with a different pitch

when struck.

5

Hitting or Plucking to Make Sound

Some instruments make sounds when you hit them They are called percussion instruments Drums are percussion instruments Drums are played with rubber hammers, wooden sticks, brushes, or your hands If you tap a drum lightly, you hear a soft sound Hitting the drum harder makes a stronger vibration This makes a louder sound

The blocks on this instrument vibrate when they are hit with

a rubber hammer.

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Stringed instruments are played in two ways You

can pluck the strings Or you can rub a bow across

them Both ways make sounds The strings are

different sizes They can be long or short and thick

or thin Some are stretched tighter than others Long,

thick strings make a lower-pitched sound Short,

thin, tight strings make faster vibrations They make

higher-pitched sounds

Have you ever heard a harp before? The strings

of this harp must be plucked to vibrate.

7

Using Air to Make Sound

The sound of your voice is made by vibrations in your windpipes When air from your lungs passes between your vocal cords, they vibrate You can speak and sing because your vocal cords vibrate When you speak, your cords tighten The tighter they get, the higher the pitch of your voice

Your vocal cords are two pairs of thin tissue

in your windpipe

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A wind instrument’s sound comes from vibrating air

inside it Blow into a trumpet Your lips vibrate against

the mouthpiece as you blow This makes the air inside

the trumpet vibrate It also makes sound

You can change the pitch of the trumpet’s sound

in two ways Change how your lips vibrate Or

press on the valves of the trumpet Pressing on the

valves changes how long the air column is inside

the trumpet

Do you know how to

play a trumpet?

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Some wind instruments use reeds A reed is a thin piece of wood It is attached to the mouthpiece When

a person blows on a reed, it vibrates The vibration makes the air inside the wind instrument vibrate

The vibrating air makes a sound If you press the keys

of the wind instrument, you can change the pitch of the sound

Clarinet

All three of these wind instruments use reeds.

Saxophone

Harmonica

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How does sound travel?

What are sound waves?

A bell rings Its vibrations move in the air Some air

particles are spread out Others are squeezed together

The particles take turns doing this This allows the

bell’s vibrations to move between these particles This

movement makes a wave called a compression

wave Sound waves are compression waves.

Sound travels as waves in the air.

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Sound waves travel through matter Some of the particles that make up matter get squeezed Other particles are spread apart The particles of matter take turns being squeezed and spread out The length of a sound wave can be measured We measure from the center of one squeezed area to the center of the next

Sound waves from a jackhammer have lots

of energy If you were standing nearby, you would hear a very loud sound Sound waves lose energy as they move away Farther away, the sound would not be as loud.

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Sound and Matter

You hear sound only when it travels through matter

Sound can travel through solids, liquids, and gases

The speed of a sound wave is different in each kind

of matter

The gases of air have particles that are far

apart Sound travels slowly through gases Liquid

particles are closer together Sound travels more

quickly through a liquid than a gas Solid particles

are closer together than gases or liquids Sound travels

fastest through solids

Light travels faster than sound

That is why you may see fireworks

before you hear them.

(meters per second) Speed of Sound

Solid—Steel Liquid—Seawater Gas—Air

5,200 1,530 340

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Echoes are sound waves that hit something and bounce back Scientists use sound waves and echoes

to study the ocean A ship sends out a sound wave

When the sound wave hits the bottom of the ocean, it bounces back Scientists measure how long the sound wave takes to bounce back Then they can figure out how deep the ocean is at that spot

Sound travels at about 1,530 meters per second

in water Some whales can make sounds that can be heard up to 160 kilometers away.

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The Ear

We hear sounds with our ears The outer ear catches

sound waves The waves travel inside the ear to the

eardrum When the sound waves hit the eardrum,

they make it vibrate The vibrating eardrum makes

little bones vibrate The little bones touch the shell-like

inner ear It is filled with liquid and tiny hairs The

vibrating little bones make the tiny hairs move The

hairs are connected to nerves The nerves carry signals

to the brain The brain recognizes the signals Then we

know what we are hearing

Inner ear Outer ear

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Many animals have vocal cords like people do

They make sounds when their vocal cords vibrate

Dogs bark Cows moo Some animals make sounds that do not use vocal cords Bees and mosquitoes make buzzing sounds when their wings vibrate

Bats send out sounds people cannot hear The sounds are high-pitched and bounce off insects

The sounds return to the bats’ ears This helps the bats find their food

Many insects make sounds by rubbing body parts together

Chimpanzees grunt, bark, squeak, scream, and even laugh.

Zebras make sounds

by vibrating their vocal cords, lips, and nostrils.

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Glossary

compression wave the wavelike movement of

particles squeezing together and spreading out again

vibration the back-and-forth movement