3 14 how sound works (physical science)

How is the pitch of a slow vibration different from the pitch of a faster vibration.. Big vibrations make loud sounds.. Small vibrations make soft sounds.. Some insects, such as the gras

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Scott Foresman Science 3.14

Nonfi ction Compare and

Contrast

• Captions

• Labels

• Diagrams

• Glossary

Sound

ISBN 0-328-13848-7

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Scott Foresman Science 3.14

Nonfi ction Compare and

Contrast

• Captions

• Labels

• Diagrams

• Glossary

Sound

ISBN 0-328-13848-7

ì<(sk$m)=bdieih< +^-Ä-U-Ä-U

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1 How is sound produced?

2 What does plucking or rubbing the

strings of a violin do?

3 Sound travels fastest through which

type of matter? Why?

you have read about sound Write

to explain how your ears help you hear sound Include details from the book

vibrations can be fast or slow

How is the pitch of a slow vibration different from the pitch of a

faster vibration?

What did you learn?

Vocabulary

compression wave

pitch

vibration

Picture Credits

Every effort has been made to secure permission and provide appropriate credit for photographic material

The publisher deeply regrets any omission and pledges to correct errors called to its attention in subsequent editions.

Photo locators denoted as follows: Top (T), Center (C), Bottom (B), Left (L), Right (R), Background (Bkgd).

13 (Bkgd, BR) Getty Images.

Scott Foresman/Dorling Kindersley would also like to thank: 3 Kim Taylor/DK Images; 15 Denoyer-Geppert

International/DK Images; 7 (TL) Stephen Oliver/DK Images.

ISBN: 0-328-13848-7

This publication is 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 form by any means, electronic,

mechanical, photocopying, recording, or likewise For information regarding permission(s), write to

Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.

3 4 5 6 7 8 9 10 V010 13 12 11 10 09 08 07 06 05

by Wendy Weiss

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What Sound Is

S I Z Z L

E S I

Z Z

L

E

S

I Z

Z L

E

R I N G

R I NG

Sounds are all around us Think about

how many sounds you hear each morning

What wakes you up in the morning? Does an

alarm clock ring? What do you eat for breakfast?

Your parents may cook eggs The eggs probably

sizzle in the frying pan These are sounds you

may hear in the morning

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Some sounds may bother you They may be

so loud that they hurt your ears Fire truck and ambulance sirens may make you cover your ears

Other sounds may bother you when you are trying to do something else

Luckily, many sounds are nice to hear Do you like to listen to music? There are many different types of music Most people have a favorite type of music they like to listen to There are sounds in nature too Maybe you like to listen

to chirping birds or a rushing river

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What sound does

an ambulance make?

IRP

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All the different sounds in the world are created

in the same way Sounds are made when matter

moves back and forth really fast A vibration is

the back-and-forth movement of matter When

something vibrates, a sound is created

Sounds can be loud or soft Loudness describes

how loud or soft sound is Big vibrations make loud

sounds Small vibrations make soft sounds Sounds

can also be high or low Pitch tells you how high

or low sound is Slow vibrations have a low pitch

Faster vibrations have a higher pitch

The vibrations of the tuning fork are causing the water to splash

Vibrating cymbal

Tuning fork

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You can learn something about vibrations when you listen to the loudness and pitch of sounds around you

When a book falls off a desk and hits the

fl oor, it makes a loud, low thud The sound

is loud The pitch is low Does that mean the vibrations are big or small? Fast or slow?

The book’s big vibrations are slow

Now think about tapping a water glass with

a spoon What type of sound would you hear?

Loud or soft? High or low?

T I NG

TI N

G

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How Sound Is Made

Let’s explore how sound is made When a book

is dropped and a glass is tapped, two different

sounds are made in two different ways Animals

are also able to make sounds in a number of ways

An elephant makes a loud, trumpeting sound

when it is upset Just like people, elephants force

air past their vocal cords in order to make a

sound Some insects, such as the grasshopper,

make chirping sounds by rubbing their wings

An elephant uses its trunk and throat to make a loud, trumpeting sound. A grasshopper uses

its wings to make

a chirping sound.

Wing Trunk

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Musical instruments make sounds in different ways too Hitting two objects together can create musical sounds Wooden blocks and sticks are great for making music Think about the pretty ringing sound a music triangle makes when you hit it with a metal rod

Can you describe the sound that two wooden sticks make when you hit them together?

What sound does a triangle make if you hit it with a metal rod?

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A violin is a stringed musical instrument

The strings make musical sounds when someone

pulls at, or plucks, them Rubbing a bow across

the strings also creates sound When you pull

at or rub the strings, they begin to move Their

vibrations make sound When you pluck a violin

string, you can make a short sound If you rub a

bow across that string, you can make a sound that

lasts as long as you want

This girl is rubbing the strings

of a violin with a bow.

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You can also use air to make sounds In order

to talk, you need to let out air The air passes over your vocal cords They make the air vibrate

The tighter your vocal cords are, the higher the pitch of your voice

Think about blowing into an empty glass bottle Does this make a sound? If you do it right, yes! Can you whistle? If you can, it is because you are able to push air out through your lips This causes the air to vibrate

Blow into bottles fi lled with liquid Does the amount

of liquid change the sound each bottle makes?

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How Sound Moves

You now know that sound is created by

vibrations You have also learned how different

sounds are made by using air, by hitting objects,

or by pulling and rubbing strings But how does

sound get from the place where it is made to

your ears?

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Sound can travel through all three forms of matter—solids, liquids, and gases Sound comes from vibrations These vibrations make particles

of matter squeeze together and move apart very, very quickly This type of vibration makes a wave

pattern that scientists call a compression wave

All sound waves are compression waves

This sound wave is traveling through the air The area

of squeezed particles moves along the wave It moves

in the direction the sound is traveling.

Area of squeezed air particles

Direction of sound wave

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We usually cannot see sound traveling through

matter Scientists have special tools to measure the

size and speed of sound waves Scientists know that

sound travels fastest through solids This is because

the particles are closest together in this form of

matter Since the particles are so close together,

they bump into each other more easily Then the

wave is able to move quickly through the particles

Sound moves the slowest through gases Gas

particles are spread far apart and cannot transfer

vibrations as easily or quickly

Sound travels

through steel

at 5,200 meters

per second

Sound travels through water

at 1,530 meters per second.

Sound travels through air

at 340 meters per second.

Ball made

of steel

Bowl of water Balloon fi lled

with air

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Some sound waves have special names Echoes are sound waves that have been traveling forward but suddenly hit a large, solid object Then the waves bounce back the way they came Echoes are fun to hear, such as when you shout your name while standing in an empty gym

Echoes are also useful Scientists use a type

of echo called sonar to fi gure out how deep the ocean is They do this by sending a sound wave

to the bottom and waiting for it to bounce back

The depth is based on how long this takes

Ships use sonar to measure ocean depths.

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How We

Hear Sounds

What happens when sounds reach your ears?

Ears are shaped to catch the sounds from all

around us Each part of the ear has a special job

Think about the shape of your ear Does it

seem silly to you? It’s actually very useful The

cuplike shape collects sounds that travel near

the ear The shape also helps move these sounds

inside the ear

As sound waves travel into the ear, the fi rst

thing they reach is the eardrum The eardrum is a

thin, skinlike layer that stretches across the inside

of the ear When sound waves hit the eardrum,

it begins to vibrate Then these vibrations move

farther into the ear

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Next, the vibrations reach three tiny bones that touch the eardrum These bones vibrate when the eardrum does They pass the sound along to the inner ear

The inner ear has a part that is shaped like

a shell and is lined with tiny hairs This part is full of liquid The vibrations from the tiny bones make the hairs in the liquid vibrate These hairs are attached to nerves that carry vibration signals

to the brain The brain then identifi es the sound

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Outer ear Eardrum Ear bones Inner ear

Parts of the ear

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compression wave a sound wave created by

the in-and-out movement

of particles of matter

create a low or high sound

movement of matter

Glossary

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