21 the nature of sound compression guide: chapter …21 the nature of sound chapter planning guide...

OBJECTIVES LABS, DEMONSTRATIONS, AND ACTIVITIES TECHNOLOGY RESOURCES

Compression guide:To shorten instructionbecause of time limitations,omit Section 4.

21 The Nature of SoundChapter Planning Guide

Chapter Opener

597A Chapter 21 • The Nature of Sound

OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P85 Sounds from a Stereo Speaker* TR P86 How the Human Ear Works* SE Internet Activity, p. 604g

CRF SciLinks Activity*gCD Science Tutor

TE Demonstration Vibrations of Stereo Speakers,p. 600g

SE Quick Lab Good Vibrations, p. 601g TE Activity Sounds in Your World, p. 601g SE Connection to Biology Vocal Sounds, p. 602g TE Group Activity Sound Samples, p. 602g TE Activity Diagrams of the Ear, p. 603b LB Whiz-Bang Demonstrations Hear Ye, Hear Ye*g LB Whiz-Bang Demonstrations Jingle Bells, Silent

Bells*g

Section 1 What Is Sound?• Describe how vibrations cause sound.• Explain how sound is transmitted through a medium.• Explain how the human ear works, and identify

its parts.• Identify ways to protect your hearing.

OSP Lesson Plans (also in print) TR Bellringer Transparency* TR P87 Frequency and Pitch* TR P88 The Doppler Effect*VID Lab Videos for Physical ScienceCD Science Tutor

TE Activity Paper Cup Phones, p. 607 ◆ g

TE Connection Activity Math, p. 607g TE Activity Doppler Diagram, p. 608b TE Demonstration The Doppler Effect in Action,

p. 608g SE Quick Lab Sounding Board, p. 609g SE School-to-Home Activity Decibel Levels, p. 610g SE Skills Practice Lab Easy Listening, p. 622g LB Whiz-Bang Demonstrations The Sounds of

Time*g

PACING • 90 min pp. 606–611Section 2 Properties of Sound• Compare the speed of sound in different media.• Explain how frequency and pitch are related.• Describe the Doppler effect, and give examples of it.• Explain how amplitude and loudness are related.• Describe how amplitude and frequency can be

“seen” on an oscilloscope.

OSP Lesson Plans (also in print) TR Bellringer Transparency* TR LINK TOLINK TO EARTH SCIENCEEARTH SCIENCE E48 How

Sonar Works* TR P89 Echolocation* TR P90 How Sonar WorksCD Science Tutor

TE Demonstration Sound Waves in Water, p. 612g TE Connection Activity Language Arts, p. 613g TE Connection Activity Real World, p. 614g TE Activity Interference in Auditoriums, p. 615a SE Inquiry Lab The Speed of Sound, p. 742g SE Skills Practice Lab Tuneful Tube, p. 743g SE Skills Practice Lab The Energy of Sound, p. 744g LB Whiz-Bang Demonstrations A Hot Tone*g

PACING • 45 min pp. 612–617Section 3 Interactions of Sound Waves• Explain how echoes are made, and describe their use

in locating objects.• List examples of constructive and destructive inter-

ference of sound waves.• Explain what resonance is.

OSP Lesson Plans (also in print) TR Bellringer Transparency* CD Interactive Explorations CD-ROM

Sound Bite!gCD Science Tutor

TE Demonstration Musical Instruments, p. 618 ◆ g

TE Demonstration Families of Instruments, p. 619g LB EcoLabs & Field Activities An Earful of Sounds*b LB Long-Term Projects & Research Ideas The Caped Ace

Flies Again*a SE Science in Action Math, Social Studies, and Language

Arts Activities, pp. 628–629g

PACING • 45 min pp. 618–621Section 4 Sound Quality• Explain why different instruments have different

sound qualities.• Describe how each family of musical instruments

produces sound.• Explain how noise is different from music.

OSP Parent Letter ■

CD Student Edition on CD-ROM CD Guided Reading Audio CD ■

TR Chapter Starter Transparency*VID Brain Food Video Quiz

SE Start-up Activity, p. 599gpp. 598–605PACING • 90 min

CRF Vocabulary Activity*g SE Chapter Review, pp. 624–625g

CRF Chapter Review* ■g

CRF Chapter Tests A* ■g, B*a, C*s SE Standardized Test Preparation, pp. 626–627g

CRF Standardized Test Preparation*gCRF Performance-Based Assessment*gOSP Test Generator, Test Item Listing

CHAPTER REVIEW, ASSESSMENT, ANDSTANDARDIZED TEST PREPARATION

PACING • 90 min

Online and Technology Resources

Visit go.hrw.com foraccess to Holt OnlineLearning, or enter thekeyword HP7 Homefor a variety of freeonline resources.

This CD-ROM package includes:• Lab Materials QuickList Software• Holt Calendar Planner• Customizable Lesson Plans• Printable Worksheets

• ExamView® Test Generator• Interactive Teacher’s Edition• Holt PuzzlePro®

• Holt PowerPoint® Resources

STANDARDS CORRELATION SKILLS DEVELOPMENT RESOURCES SECTION REVIEW AND ASSESSMENT CORRELATIONS

Chapter 21 • Chapter Planning Guide 597B

CRF Directed Reading A* ■b, B*s IT Interactive Textbook* Struggling ReadersStruggling Readers

CRF Vocabulary and Section Summary* ■g

SE Reading Strategy Prediction Guide, p. 600g TE Inclusion Strategies, p. 601 TE Support for English Language Learners, p. 603

SE Reading Checks, pp. 601, 602, 604g TE Homework, p. 602g TE Reteaching, p. 604b TE Quiz, p. 604g TE Alternative Assessment, p. 604g SE Section Review,* p. 605 ■g

CRF Section Quiz* ■g

SAI 1, 2; SPSP 1; PS 3a



SE Reading Strategy Reading Organizer, p. 606g SE Math Practice The Speed of Sound, p. 607g TE Support for English Language Learners, p. 608

CRF Reinforcement Worksheet Doppler Dan’s Dump Truck*b

SE Reading Checks, pp. 607, 609, 610g TE Reteaching, p. 610b TE Quiz, p. 610g TE Alternative Assessment, p. 610g SE Section Review,* p. 611 ■g


UCP 1, 3; SAI 1, 2; PS 3a;Chapter Lab: SAI 1, 2



SE Reading Strategy Paired Summarizing, p. 612g TE Inclusion Strategies, p. 613 TE Support for English Language Learners, p. 614

SE Reading Checks, pp. 613, 614, 616g TE Reteaching, p. 616b TE Quiz, p. 616g TE Alternative Assessment, p. 616g SE Section Review,* p. 617 ■g


UCP 1; PS 3a



SE Reading Strategy Reading Organizer, p. 618g TE Reading Strategy Prediction Guide, p. 619g TE Support for English Language Learners, p. 619

CRF Critical Thinking The Noise Police*a

SE Reading Checks, pp. 619, 621g TE Homework, p. 619g TE Reteaching, p. 620b TE Quiz, p. 620g TE Alternative Assessment, p. 620g SE Section Review,* p. 621 ■g


UCP 5

SE Pre-Reading Activity, p. 598gOSP Science Puzzlers, Twisters & Teasers*g

National ScienceEducation Standards

SAI 1, 2

CRF Chapter Resource File SS Science Skills Worksheets IT Interactive TextbookOSP One-Stop Planner MS Math Skills for Science Worksheets * Also on One-Stop Planner

SE Student Edition LB Lab Bank CD CD or CD-ROM ◆ Requires advance prepTE Teacher Edition TR Transparencies VID Classroom Video/DVD ■ Also available in Spanish

KEY

Maintained by the NationalScience Teachers Association.See Chapter Enrichment pagesthat follow for a complete listof topics.

www.scilinks.orgCheck out Current Sciencearticles and activities byvisiting the HRW Web siteat go.hrw.com. Just typein the keyword HP5CS21T.

• Lab Videos demonstratethe chapter lab.

• Brain Food Video Quizzeshelp students review thechapter material.

ClassroomVideos

Holt Lab GeneratorCD-ROM

Search for any lab by topic, standard,difficulty level, or time. Edit any labto fit your needs, or create your ownlabs. Use the Lab Materials QuickListsoftware to customize your labmaterials list.

• Guided Reading Audio CD(Also in Spanish)

• Interactive Explorations• Virtual Investigations• Visual Concepts• Science Tutor

ClassroomCD-ROMs

Planning ResourcesTEST ITEM LISTINGPARENT LETTERLESSON PLANS

Visual ResourcesCHAPTER STARTER

TRANSPARENCYBELLRINGER

TRANSPARENCIES

CONCEPT MAPPING TRANSPARENCYTEACHING TRANSPARENCIES

TEACHING TRANSPARENCIES

TEST ITEM LISTING

Copyright © by Holt Rinehart and Winston All rights reserved

The World of ScienceMULTIPLE CHOICE

1. A limitation of models is thata. they are large enough to see.b. they do not act exactly like the things that they model.c. they are smaller than the things that they model.d. they model unfamiliar things.Answer: B Difficulty: I Section: 3 Objective: 2

2. The length 10 m is equal toa. 100 cm. c. 10,000 mm.b. 1,000 cm. d. Both (b) and (c)Answer: B Difficulty: I Section: 3 Objective: 2

3. To be valid, a hypothesis must bea. testable. c. made into a law.b. supported by evidence. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2 1

4. The statement "Sheila has a stain on her shirt" is an example of a(n)a. law. c. observation.b. hypothesis. d. prediction.Answer: B Difficulty: I Section: 3 Objective: 2

5. A hypothesis is often developed out ofa. observations. c. laws.b. experiments. d. Both (a) and (b)Answer: B Difficulty: I Section: 3 Objective: 2

6. How many milliliters are in 3.5 kL?a. 3,500 mL c. 3,500, 000 mLb. 0.0035 mL d. 35,000 mLAnswer: B Difficulty: I Section: 3 Objective: 2

7. A map of Seattle is an example of aa. law. c. model.b. theory. d. unit.Answer: B Difficulty: I Section: 3 Objective: 2

8. A lab has the safety icons shown below. These icons mean that you should weara. only safety goggles. c. safety goggles and a lab apron.b. only a lab apron. d. safety goggles, a lab apron, and gloves.Answer: B Difficulty: I Section: 3 Objective: 2

9. The law of conservation of mass says the tot al mass before a chemical change isa. more than the total mass after the change.b. less than the total mass after the change.c. the same as the total mass after the change.d. not the same as the total mass after the change.Answer: B Difficulty: I Section: 3 Objective: 2

10. In which of the following areas might you find a geochemist at work?a. studying the chemistry of rocks c. studying fishesb. studying forestry d. studying the atmosphereAnswer: B Difficulty: I Section: 3 Objective: 2

TEACHER RESOURCE PAGE

Lesson Plan

Section: Waves

PacingRegular Schedule: with lab(s): 2 days without lab(s): 2 days

Block Schedule: with lab(s): 1 1/2 days without lab(s): 1 day

Objectives1. Relate the seven properties of life to a living organism.

2. Describe seven themes that can help you to organize what you learn aboutbiology.

3. Identify the tiny structures that make up all living organisms.

4. Differentiate between reproduction and heredity and between metabolismand homeostasis.

National Science Education Standards CoveredLSInter6: Cells have particular structures that underlie their functions.

LSMat1: Most cell functions involve chemical reactions.

LSBeh1:Cells store and use information to guide their functions.

UCP1:Cell functions are regulated.

SI1: Cells can differentiate and form complete multicellular organisms.

PS1: Species evolve over time.

ESS1: The great diversity of organisms is the result of more than 3.5 billion yearsof evolution.

ESS2: Natural selection and its evolutionary consequences provide a scientificexplanation for the fossil record of ancient life forms as well as for the strikingmolecular similarities observed among the diverse species of living organisms.

ST1: The millions of different species of plants, animals, and microorganismsthat live on Earth today are related by descent from common ancestors.

ST2: The energy for life primarily comes from the sun.

SPSP1: The complexity and organization of organisms accommodates the needfor obtaining, transforming, transporting, releasing, and eliminating the matterand energy used to sustain the organism.

SPSP6: As matter and energy flows through different levels of organization ofliving systems—cells, organs, communities—and between living systems and thephysical environment, chemical elements are recombined in different ways.

HNS1: Organisms have behavioral responses to internal changes and to externalstimuli.

This CD-ROM includes all of the resources shown here and the following time-saving tools:

• Lab Materials QuickList Software

• Customizable lesson plans

• Holt Calendar Planner

• The powerful ExamView ® Test Generator

Chapter Resources

Dear Parent,

Your son's or daughter's science class will soon begin exploring the chapter entitled “The

World of Physical Science.” In this chapter, students will learn about how the scientific

method applies to the world of physical science and the role of physical science in the

world. By the end of the chapter, students should demonstrate a clear understanding of the

chapter’s main ideas and be able to discuss the following topics:

1. physical science as the study of energy and matter (Section 1)

2. the role of physical science in the world around them (Section 1)

3. careers that rely on physical science (Section 1)

4. the steps used in the scientific method (Section 2)

5. examples of technology (Section 2)

6. how the scientific method is used to answer questions and solve problems (Section 2)

7. how our knowledge of science changes over time (Section 2)

8. how models represent real objects or systems (Section 3)

9. examples of different ways models are used in science (Section 3)

10. the importance of the International System of Units (Section 4)

11. the appropriate units to use for particular measurements (Section 4)

12. how area and density are derived quantities (Section 4)

Questions to Ask Along the Way

You can help your son or daughter learn about these topics by asking interesting questions

such as the following:

• What are some surprising careers that use physical science?

• What is a characteristic of a good hypothesis?

• When is it a good idea to use a model?

• Why do Americans measure things in terms of inches and yards instead of centimeters

and meters ?

Copyright © by Holt, Rinehart and Winston. All rights reserved.

Explo

ring th

e Ocean

sTEA

CHIN

G TR

AN

SPAR

ENCY

How Sonar W

orksScientists use sonar signals to m

ake a bathymetric profile, w

hich is a m

ap of the ocean floor that show

s the ocean’s depth.

The longer it takes for the sound to bounce off the ocean floor and return to the ship, the deeper the floor is in that spot.

To map a section of the

ocean floor, scientists travel by ship across the ocean’s surface. As they m

ove, they repeatedly send sonar signals to the ocean floor.

1

2

3

597C Chapter 21 • The Nature of Sound

21

Would You Believe . . . ?

The Nature of Sound CHAPTER STARTER

In 1271, the Italian explorer Marco Polobegan his historic journey to China withhis father and uncle. He was only 17years old. Though he didn’t know it atthe time, 24 years would pass before heand his companions would return hometo Venice, Italy.

Upon his return, Marco Polo wroteof the many incredible things he hadobserved while in Asia. One such thingwas the booming sand dunes of theAsian desert. Marco Polo wrote how thesands actually made noises, filling theair with sounds of music, drums, andweapons of war.

Although they were a mystery duringMarco Polo’s time, much has beenlearned about these booming sands. Forexample, they are most often found inthe middle of large deserts. The loud,low-pitched sounds—which have beencompared to foghorns, cannon fire, andmoaning—can last from a few secondsto 15 minutes and can be heard morethan 10 km away! Booming sands havebeen discovered all over the world,including the United States.

Scientists have learned that the loudsounds are caused by avalanches of sandwithin a dune. As the top layers of sandslip over the layers below, vibrations are

produced that create the strange sounds.However, scientists are still not sure whythese sands make noise and other sandsdo not.

Although there is still much to learnabout booming sands, the nature of soundis well understood. In this chapter, youwill learn about sound, its properties, andhow sound waves interact to influenceyour life.

Marco Polo

Sand Mountain, in Nevada, makes low droning sounds.


The Nature of Sound BELLRINGER TRANSPARENCY


Section: What Is Sound?If you’ve ever been near a large fireworks display,you may have felt the sound of the explosions. Thinkof other instances when you might feel sound anddescribe them in your science journal.

Section: Properties of SoundYou are the commander of a space station locatedabout halfway between Earth and the moon. You are in the Command Center, and your chief ofsecurity tells you that sensors have just detected anexplosion 61.054 km from the station. How long will it be before you hear the sound of the explosion?

Record your answer in your science journal, andthen share your answers with the group.

Sounds from a Stereo SpeakerThe Nature of Sound TEACHING TRANSPARENCY


Electrical signals make the speaker vibrate. As the speaker cone moves forward, it pushes the air particles in front of it closer together, creating a region of higher density and pressure called a compression.

a

As the speaker cone moves backward, air particles close to the cone become less crowded, creating a region of lower density and pressure called a rarefaction.

b

For each vibration, a compression and a rarefaction are formed. As the compressions and rarefactions travel away from the speaker, sound is transmitted through the air.

c

How the Human Ear WorksThe Nature of Sound TEACHING TRANSPARENCY


Pinna

Ear canal

HammerAnvil

Stirrup

Eardrum

Cochlea

Sound waves vibrate the eardrum—alightly stretched membrane that is the entrance to the middle ear.

The vibration of the eardrum makes the hammer vibrate, which, in turn, makes the anvil and stirrup vibrate.

The stirrup vibrates the oval window—the entrance to the inner ear.

The vibrations of the oval window create waves in the liquid inside the cochlea.

Movement of the liquid causes tiny hair cells in-side the cochlea to bend.

The bending of the hair cells stimulates nerves, which send electrical signals to the brain.

In the middle ear, three bones—the hammer, anvil, and stirrup—act as levers to increase the size of the vibrations.

In the inner ear, vibra-tions created by sound are changed into electrical signals for the brain to interpret.

b ca The outer ear acts as a funnel for sound waves. The pinna collectssound waves and directs them into the ear canal.

1

2

3 4

56


The N

ature o

f Sou

nd

TEACH

ING

TRA

NSPA

REN

CY

Frequency and Pitch

High

frequ

ency �

high

pitch

Low

frequ

ency �

low

pitch


The N

ature o

f Sou

nd

TEACH

ING

TRA

NSPA

REN

CY

The Doppler Effect

A car w

ith its horn honking moves

toward the sound w

aves going in the sam

e direction. A person in front of the car

hears sound waves that are closer together.

The car moves aw

ay from the sound w

aves going in the opposite direction. A

person behind the car hears sound w

aves that are farther apart and have a low

er frequency.

ba

ab

waves combine by waves require a is described by

which dependson

which can be representedusing an

which dependson

amplitude

The Nature of Sound CONCEPT MAPPING TRANSPARENCY


Use the following terms to complete the concept map below:loudness, oscilloscope, frequency, sound, interference, pitch, medium

Chapter: Exploring the Oceans

SAMPLE SAMPLE SAMPLE

Meeting Individual Needs

Review and Assessments

Labs and Activities

DIRECTED READING A VOCABULARY ACTIVITY REINFORCEMENT

ECOLABS &FIELD ACTIVITIES

DATASHEETS FORQUICKLABS

DATASHEETS FORQUICK LABS

STANDARDIZED TESTPREPARATIONCHAPTER TEST BCHAPTER REVIEWSECTION QUIZ

SCILINKS ACTIVITY

MARINE ECOSYSTEMS

Go to www.scilinks.com. To find links relatedto marine ecosystems, type in the keywordHL5490. Then, use the links to answer thefollowing questions about marine ecosys-tems.

1. What percentage of the Earth’s surface iscovered by water?

2. What percentage of the Earth’s water is found in the oceans?

3. What is the largest animal on Earth?

4. Describe an ocean animal.

Name Class Date

SciLinks ActivityActivity

Developed and maintained by theNational Science Teachers Association

Topic: Reproductive SystemIrregularitiesSciLinks code: HL5490


Name Class Date

Vocabulary ActivityActivity

Getting the Dirt on the SoilAfter you finish reading Chapter: [Unique Title], try this puzzle! Use the clues belowto unscramble the vocabulary words. Write your answer in the space provided.

1. the breakdown of rock intosmaller and smaller pieces:AWERIGNETH

2. layer of rock lying beneath soil:CROKDEB

3. type of crop that is plantedbetween harvests to reduce soilerosion: CROVE

4. action of rocks and sedimentscraping against each other andwearing away exposed surfaces:SABRONIA

5. a mixture of small mineral frag-ments and organic matter: LISO

6. rock that is a source of soil:PRATEN CORK

7. type of reaction that occurs whenoxygen combines with iron toform rust: oxidation

8. type of weathering caused byphysical means: CLEMANIACH

9. the chemical breakdown of rocksand minerals into newsubstances: CAMILCHETHEARIGWEN

10. layers of soil, to a geologist:SNORHIZO

11. the uppermost layer of soil:SPOTOIL

12. process in which rainwater car-ries dissolved substances fromthe uppermost layers of soil to thebottom layers: HELANCIG

13. small particles of decayed plantand animal material in soil:MUUSH

14. the process in which wind, water,or ice moves soil from onelocation to another: ROOSINE

15. the methods humans use to takecare of soil:OSIL VASETONRICON

WHIZ-BANGDEMONSTRATIONS


VOCABULARY ANDSECTION SUMMARY


Section: EnergIn the space provided, write the letter of the description that best matches theterm or phrase.

______ 1. building molecules that can be used asan energy source. or breaking down moleculesin which energy is stored

______ 2. the process by which light energy is convertedto chemical energy

______ 3. an organism that uses sunlight or inorganicsubstances to make organic compounds

______ 4. an organism that uses sunlight or inorganicsubstances to make organic compounds

______ 5. an organism that consumes food to get energy

______ 6. the process of getting energy from food

In the space provided, write the letter of the term or phrase that best completeseach statement or best answers each question.

Name Class Date

Section QuizAssessment

a. photosynthesis

b. autotroph

c. heterotroph

d. cellular respiration

e. metabolism

f. cellular respiration

______ 7. Which of the following mostclosely resembles cellularrespiration?a. warm water moving

through copper pipesb. people movimg alomg a

escalatorc. mixing different foods in

a blenderd. logs burning in a fire

______ 8. An organism’s reproductivecells, such as sperm or eggcells, are called?a. genesb. chromosomesc. gamates.d. zygotes.

______ 9. An organism’s reproductivecells, such as sperm or eggcells, are called?a. genesb. chromosomesc. gamates.d. zygotes.

______10. Which of the following mostclosely resembles cellularrespiration?a. warm water moving

through copper pipesb. people movimg alomg a

escalatorc. mixing different foods in

a blenderd.

logs burning in a fire


Section: ExploringTHAT’S SCIENCE!

1. How did James Czarnowski get his idea for the penguin boat, Proteus?Explain.

2. What is unusual about the way that Proteus moves through the water?

MATTER + AIR ➔ PHYSICAL SCIENCE

3. What do air, a ball, and a cheetah have in common?

4. What is one question you will answer as you explore physical science?

5. Chemistry and physics are both fields of . Chemists

study the different forms of and how they interact.

and how it affects are

studied in physics.

Identify the field of physical science to which each of the following descriptionsbelongs by writing physics or chemistry in the space provided.

_______________________ 6. how a compass works

_______________________ 7. why water boils at 100°C

_______________________ 8. how chlorine and sodium combine to form table salt

_______________________ 9. why you move to the right when the car you are inturns left

Directed Reading A

Name Class Date

Skills Worksheet

DIRECTED READING B

Section: ExploringTHAT’S SCIENCE!

1. How did James Czarnowski get his idea for the penguin boat, Proteus?Explain.

2. What is unusual about the way that Proteus moves through the water?

MATTER + AIR ➔ PHYSICAL SCIENCE

3. What do air, a ball, and a cheetah have in common?

Directed Reading B

Name Class Date

Skills Worksheet

Section: UniqueVOCABULARY

In your own words, write a definition of the following term in the space provided.

1. scientific method

2. technology

3. observation

Name Class Date

Vocabulary & NotesSkills Worksheet

Name Class Date

ReinforcementSkills Worksheet

The Plane TruthComplete this worksheet after you finish reading the Section: [Unique SectionTitle]

You plan to enter a paper airplane contest sponsoredby Talkin’ Physical Science magazine. The personwhose airplane flies the farthest wins a lifetime sub-scription to the magazine! The week before the con-test, you watch an airplane landing at a nearbyairport. You notice that the wings of the airplane haveflaps, as shown in the illustration at right. The paperairplanes you’ve been testing do not have wing flaps.What question would you ask yourself based on these observations? Write yourquestion in the space below for “State the problem.” Then tell how you could usethe other steps in the scientific method to investigate the problem.

1. State the problem.

2. Form a hypothesis.

3. Test the hypothesis.

4. Analyze the results.

5. Draw conclusions.

Flaps


CRITICAL THINKING

A Solar Solution

Name Class Date

Critical ThinkingSkills Worksheet

Joseph D. Burns

Inventors’ Advisory Consultants

Portland, OR 97201

Dear Mr. Burns,I’ve got this great idea for a new product called the BlissHeater. It’s a portable, solar-powered space heater. The heater’s design includes these features:•T

he heater will be as longas an adult’s arm and aswide as a

packing box.

•T

he heater will have aglass top set at an angleto catch the sun’s rays.

•T

he inside of the heaterwill be dark colored toabsorb solar heat.If you think my idea will work, I will make the Bliss

Heaters right away without wasting time and money on test-ing and making models. Please write back soon with youropinion.

SECTION REVIEW

Section: UniqueKEY TERMS

1. What do paleontologist study?

2. How does a trace fossil differ from petrified wood?

3. Define fossil.

UNDERSTANDING KEY IDEAS

Name Class Date

Section ReviewSkills Worksheet


[UniqueMULTIPLE CHOICE


______ 1. Surface currents are formed bya. the moon’s gravity. c. wind.b. the sun’s gravity. d. increased water density.

______ 2. When waves come near the shore,a. they speed up. c. their wavelength increases.b. they maintain their speed. d. their wave height increases.

______ 3. Longshore currents transport sedimenta . out to the open ocean. c. only during low tide.b. along the shore. d. only during high tide.

______ 4. Which of the following does NOT control surface currents?a. global wind c. Coriolis effectb. tides d. continental deflections

______ 5. Whitecaps breaka. in the surf. c. in the open ocean.b. in the breaker zone. d. as their wavelength increases.

______ 6. Most ocean waves are formed bya . earthquakes. c. landsides.b. wind. d. impacts by cosmic bodies.

______ 7. Which factor controls surface currents?a. global winds c. continental deflectionb. the Coriolis effect d. all of the above

______ 8. Streamlike movments of ocean water far below the surface arecalleda. jet currents c. surface currents.b. Coriolis currents. d. deep currents.

______ 9. When the sunlit part of the moon that can be seen from Earthgrows larger, it isa. waxing. c. in the new moon phase.b. waning. d. in the full moon phase.

______10. The Milky Way is thought to bea. an elliptical galaxy. c. a spiral galaxy.

Name Class Date

Chapter Test BAssessment


READING

Read the passages below. Then, read each question that follows the passage.Decide which is the best answer to each question.

Passage 1 adventurous summer camp in the world. Billy can’twait to head for the outdoors. Billy checked the recommendedsupply list: light, summer clothes; sunscreen; rain gear; heavy,down-filled jacket; ski mask; and thick gloves. Wait a minute! Billythought he was traveling to only one destination, so why does heneed to bring such a wide variety of clothes? On further investiga-tion, Billy learns that the brochure advertises the opportunity to“climb the biomes of the world in just three days.” The destinationis Africa’s tallest mountain, Kilimanjaro.

______ 1. The word destination in this passage meansA camp B vacation.C place. D mountain.

______ 2. Which of the following is a FACT in the passage?F People ski on Kilimanjaro.G Kilimanjaro is Africa’s tallest mountain.H It rains a lot on Kilimanjaro.J The summers are cold on Kilimanjaro.

______ 3. Billy wondered if the camp was advertising only one destination afterhe read the brochure, which said thatA the camp was the most adventurous summer camp in the world.B he would need light, summer clothes and sunscreen.C he would need light, summer clothes and a heavy, down-filled

jacket.D the summers are cold on Kilimanjaro.

Name Class Date

Standardized Test PreparationAssessment

PERFORMANCE-BASEDASSESSMENT

OBJECTIVEDetermine which factors cause some sugar shapes to break down faster than others.

KNOW THE SCORE!As you work through the activity, keep in mind that you will be earning a gradefor the following:

• how you form and test the hypothesis (30%)

• the quality of your analysis (40%)

• the clarity of your conclusions (30%)

ASK A QUESTIONSWhy do some sugar shapes erode more rapidly than others?

MATERIALS AND EQUIPMENT

Name Class Date

Performanced-Based AssessmentAssessment SKILL BUILDER

Using Scientific Methods

• 1 regular sugar cube • 90 mL of waterCopyright © by Holt, Rinehart and Winston. All rights reserved.

USING VOCABULARY

1. Define biome in your own words.

2. Describe the characteristics of a savanna and a desert.

3. Identify the relationship between tundra and permafrost.

4. Compare the open-water zone and the deep-water zone.

5. Use each of the following terms in an original sentence: plankton, littoralzone, and estuary.

6. Describe how marshes and swamps differ.

Name Class Date

Chapter ReviewSkills Worksheet

SCIENCE PUZZLERS,TWISTERS & TEASERS

CHAPTER TEST A






______ 4. Which of the following does NOT control surface currents?a global wind c Coriolis effect

Name Class Date

Chapter Test AAssessment

CHAPTER TEST C






______ 4. Which of the following does NOT control surface currents?a global wind c Coriolis effect

Name Class Date

Chapter Test CAssessment

For a preview of available worksheets covering math and science skills,see pages T26–T33. All of these resources are also on the One-Stop Planner®.

An Earful of Sounds

STUDENT WORKSHEET

FIELD ACTIVITY

22

Name Date Class

You are a composer and a master of 15 different instruments, including yourown voice. Usually, you are the toast of the town, but lately you have been ac-cused of noise pollution!

Perhaps the accusations have something to do with your new “musical”pieces, which use recordings of everyday sounds against a musical background.What’s wrong with your Car Horn Sonata and your Cuckoo Clock Concerto?They’re not loud; they’re just different!

Well, maybe your music does pollute a little. But if you could figure outwhat noise pollution is, you could make your music more soothing to the un-trained ear.

After writing down all the sounds from your musical pieces, you try to thinkof sounds that others might find pleasing. Then you decide to compile a collec-tion of sounds by doing a sound scavenger hunt!

You had better hurry! You play in Carnegie Hall in 2 weeks!

ObjectiveObserve and record sounds in different environments to formu-late a personal definition of noise pollution.

A Scavenger Hunt of Sounds1. Review the Sounds Checklist on page 94. As a group, add

five more sounds that you think others would find pleasing(e.g., the purring of a cat).

2. Decide where to find these sounds. Divide the list, and as-sign part of the list to each group member.

3. At home: Record at least 10–30 seconds of each sound. Placea check in the box beside each item recorded. Pack your cas-sette tape in your bag to bring to class.

4. In the table on page 94, indicate the loudness and pitch ofeach sound.

5. In class: On a separate sheet of paper, sign your full name.

6. Play the taped recordings. As you listen, write a mirrorimage of your signature. Do any sounds make it difficultto concentrate on this task? Do any sounds help youconcentrate?

7. Fill out the last column on page 94 for every sound.

8. In your ScienceLog, list the sounds that you would likeincluded in your symphony.

9. What sounds cannot be included in your symphony?Describe those sounds in your ScienceLog.

MATERIALS

• tape recorder• blank cassette tape• 2–4 pairs of earplugs• various objects that

make sound• 2 batteries

SAFETY ALERT!

Protect your hearing!Wear earplugs whilerecording loud noises.

USEFUL TERMS

loudnesshow loud or soft asound is

pitchthe highness or lownessof a sound

Chapter 21 • Chapter Resources 597D

Wordy Numbers1. Vanity phone numbers are numbers that can be spelled out in

easy-to-remember words. For example, a car dealer might choosethe number 289-2277, which can be spelled as BUY CARS. Whatword from the chapter could each of the numbers below represent?

Name _______________________________________________ Date ________________ Class______________

SCIENCE PUZZLERS, TWISTERS & TEASERS21

The Nature of Sound

CHAPTER

1 2ABC

3DEF

4GHI

5JKL

6MNO

7PRS

8TUV

9WXY

* 0 #

TEACHER-LED DEMONSTRATION

DEMO

61

Purpose

Students learn how air moving through apipe can produce sound.

Time Required

15–20 minutes

Safety Information

Use extreme caution with a lit torch. Wearprotective eyewear, and do not point theflame toward other people or materials.Do not place the PVC pipe too close to theflame—PVC can melt and give off danger-ous fumes. Students should stand clear ofthe demonstration area. Have an adultpresent to assist with this demonstration.

What to Do

1. Show students the pieces of pipe. Askthem how the pipes might be used tocreate sounds. (Sample answer: The pipescould be hit or blown into to createsounds.) Tell students that you are goingto use the Bunsen burner or torch toproduce sounds in the pipes.

2. To keep the air flowing uniformly inthe largest pipe, insert the wire-meshscreen a few inches from the top sothat it is lodged horizontally inside thepipe.

3. Use the ignitiondevice to light thepropane torch orBunsen burner,and adjust it to thehottest setting.

4. If you are usingthe torch, have an-other adult holdthe torch so thatthe flame ispointed toward theceiling.

5. While wearingheat-resistantgloves, hold theshortest pipe vertically about 20–30 cmover the flame. Slowly lower the pipeover the flame until the pipe begins toemit a tone. Experiment to find theheight that results in the loudest tone.Ask students to match the pitch byhumming.

continued...

A Hot Tone

TEACHER PREP

CONCEPT LEVEL

CLEAN UP

E A S Y H A R D

Lab Ratings

MATERIALS

• several pieces of PVC pipe 5–6 cm in diame-ter and 60–150 cm in length

• pipe 12–13 cm in diameter and 1 m inlength

• circular piece of mesh screen or hardwarecloth 12–13 cm in diameter, cut to fit snuglyinside the largest pipe

• Bunsen burner or propane torch• ignition device, such as flint• heat-resistant gloves

HELPFUL HINTS

Plumbing supply stores sometimes have scrapsof PVC pipe available at reduced prices.

Alyson MikeRadley Middle SchoolEast Helena, Montana



DEMO

62

Jingle Bells, Silent BellsPurpose

Students learn that sound waves musttravel through a medium in order to beaudible.

Time Required

20–25 minutes

flask from the heat. Do not boil awaythe water.

4. Quickly insert the bell assembly intothe flask. Don’t let the bell touch thewater. Let the flask cool for 1 minute.While wearing heat-resistant gloves,shake the flask. Tell students to listencarefully. Ask: Can you hear the bell?(Students should hear only a faint sound,if any sound at all.)

5. Loosen the stopper so that air can enterthe flask. Then replace the stopper, andshake again. Ask: Can you hear the bellnow? (Students should be able to hear thebell clearly.)

Explanation

The boiling water in the open flask pro-duced steam, which expanded in the flaskand displaced many of the air molecules.When the flask was plugged and removed

MATERIALS

• 10 cm piece of wire clothes hanger• small bell• one-hole rubber stopper• small amount of modeling clay• boiling flask

TEACHER PREP

CONCEPT LEVEL

CLEAN UP

E A S Y H A R D

Lab Ratings


DEMO

63

Purpose

Students learn how the eardrum works.

Time Required

10–20 minutes

Advance Preparation

Remove both ends of the can with a canopener. Beware of the sharp edges. Cut apiece from the balloon that is largeenough to stretch over one end of the can.Stretch the piece of balloon over one endof the can, and secure it tightly with arubber band. Glue the mirror, slightly off-center, onto the outside of the balloon,and allow it to dry.

What to Do

1. Ask students if they know how theireardrum works. (Accept all reasonableanswers.) Tell them that you will use amodel of an eardrum to demonstrate itsfunction.

2. Shine the flashlight or laser pointer onthe mirror so that the light reflectsonto a wall or movie screen and can beseen by the entire class. You may wishto dim the lights in order to see the im-age more clearly.

3. Ask several students to speak loudlyinto the open end of the can one at atime. Alternatively, you may wish touse a tuning fork or musical instru-ment. Students should observe that theimage vibrates as sound is produced inthe can.

4. Encourage students to have fun makingdifferent sounds by playing differentinstruments or using different voices atdifferent volumes and pitches.Challenge students to determine howthe movement of the image changes inresponse to changes in the sound.

continued...

Hear Ye, Hear Ye

MATERIALS

• soup can or coffee can• can opener• large balloon• large rubber band• bottle of glue• mirror, about 2 � 2 cm• flashlight, or laser pointer• blank wall or projection screen

HELPFUL HINTS

You may wish to make two model eardrums sothat students can compare the motion of thetwo images for different sounds.

Mirror

Rubberband

Membrane

TEACHER PREP

CONCEPT LEVEL

CLEAN UP

E A S Y H A R D

Lab Ratings

Kathy LaRoeRadley Elementary School

East Helena, Montana

Copyright © by Holt, Rinehart and Winston. All rights reserved.Copyright © by Holt, Rinehart and Winston. All rights reserved.


Name Class Date

Reaction to StressQuick Lab DATASHEET FOR QUICK LAB

BackgroundThe graph below illustrates changes that occur in the membrane potential of aneuron during an action potential. Use the graph to answer the followingquestions. Refer to Figure 3 as needed.

Analysis1. Determine about how long an action potential lasts.

2. State whether voltage-gated sodium, chanels are open or closed at point A.

3. State whether voltage-gated potassium channels are open or closed atpoint B.

4. Critical Thinking Recognizing Relationships What causes the menberneotential to become less negative at point A?

5. Critical Thinking Recognizing Relationships What causes the membranepotential to become more negative at point B?


Answer here.

Answer here.

Answer here.

Answer here.

Answer here.

Using Scientific Methods

LONG-TERM PROJECTS &RESEARCH IDEAS

Narrator: Good evening, and welcome to Radio KAPE for another episode of TheCaped Ace. [whooshing air] The Ace flies through the city, searching for those inneed. No danger is too great for our valiant hero. [child crying] Itisn’t long before he hears the faint sounds of distress with hissuper-sensitive super-ears. Finally, he spots the trouble.

Ace: Never fear, I am here! [flapping cape]Child: Aaack! Who are you, and why are you wearing pajamas?Ace: ‘Tis I, the Caped Ace, here to help you. [twinkle]Child: I can’t get my bike to work, and I’m late for school.

[clank of bike]Ace: It looks like you’re missing a wheel. [metallic clanging]Child: Yeah, that’s what I thought.Ace: Well, I always keep a spare in my superhero kit. Here.

[repair noises]Child: Wow! Thanks, Caped Ace!

Sound Stage1 Ever wonder how those crazy sounds on the radio are

Name ___________________________________________________ Date _________________ Class _____________

PROJECT

STUDENT WORKSHEET71

The Caped Ace Flies Again

SUGGESTEDMATERIALS



DEMO

64

Purpose

Students observe the Doppler effect in thisdramatic demonstration.

Time Required

5–10 minutes

What to Do

1 S th d f th t i t th t

so, you would like for them to listencarefully for changes in the sound.

4. Set off the alarm. Holding the otherend of the rope, swing the alarm clockabove your head.

Discussion

Use the following questions as a guide toencourage class discussion:

• Ask students: How does the soundchange as the clock moves in a circle?(Expected answer: The pitch of the soundincreases and decreases as the clock movesin a circle.)

• Why did you hear different pitches fromthe alarm? (Sample answer: Although thealarm clock emitted a constant wavelengthof sound, the waves were crowded as theyreached me. Therefore, the observed fre-quency was higher in front of the clock and

The Sounds of Time

MATERIALS

• alarm clock with handle• piece of string, 1 m long

TEACHER PREP

CONCEPT LEVEL

CLEAN UP

E A S Y H A R D

Lab Ratings

GENERAL

GENERAL

GENERALGENERAL

GENERAL

GENERAL

GENERAL

GENERAL

GENERAL

SPECIAL NEEDS

SPECIAL NEEDS GENERAL

GENERAL

GENERAL

GENERAL

GENERAL

SAMPLE

SAMPLE SAMPLE

SAMPLE SAMPLE

SAMPLE

SAMPLE

SAMPLE

SAMPLESAMPLE

SAMPLE

SAMPLE

SAMPLE

SAMPLE

SAMPLE

DATASHEETS FORCHAPTER LABS

Teacher’s NotesTIME REQUIRED

One 45-minute class period.

RATINGTeacher Prep–3Student Set-Up–2Concept Level–2Clean Up–2

MATERIALS

The materials listed on the student page are enough for a group of 4–5 students.Large, dried beans of any kind will work well in this exercise.

SAFETY CAUTION

Remind students to review all safety cautions and icons before beginning this labactivity.

Using Scientific MethodsSkills Practice Lab DATASHEET FOR CHAPTER LAB


1 2 3 4Easy Hard

Jason MarshMontevideo High

and Country School

SAMPLE

DATASHEETS FORLABBOOK

Teacher’s NotesTIME REQUIRED

One 45-minute class period.

Does It All Add Up?Skills Practice Lab DATASHEET FOR LABBOOK LAB


Jason MarshMontevideo High

SAMPLE

SAMPLE

597E Chapter 21 • The Nature of Sound

Chapter Enrichment

This Chapter Enrichment provides relevant and

interesting information to expand and enhance

your presentation of the chapter material.

What Is Sound?Robert Boyle (1627–1691)• Robert Boyle, a British scientist who lived in Ireland,

performed a famous experiment in 1660. When a bell was suspended in a vacuum, the clapper could be seen striking the bell, but no sound was heard. This demonstration proved that sound requires a medium to propagate.

Is That a Fact!◆ Singing sand dunes can make two very different

sounds: some dunes “whistle” or “squeak” in the 500 Hz to 2,500 Hz range, but others “boom” at frequencies of 50 Hz to 300 Hz. Interestingly, the booming sands can be felt as well; the dune trembles noticeably as it booms.

◆ Only sand grains with certain sizes and shapes whistle or squeal. Sands in many locations, including beach sands in a variety of places, can be induced to whistle. Scientists are less certain what factors create booming dunes, although grains of a certain size and shape seem to be required.

Properties of SoundLoudness• Loudness is expressed in decibels. An increase of

10 dB multiplies the intensity of a sound by 10 times. An increase of 20 dB is 10 � 10, or 100 times more intense. The human ear, however, responds logarithmi-cally, not linearly, to intensity.

Doppler Effect• In 1842, the Doppler effect was explained by the

Austrian physicist Christian Doppler (1803–1853). He noted that there is a change in wavelength of both light and sound when either the source or the receiver (or both, if they move at different velocities) moves.

• In acoustical Doppler effects, the frequency depends on the velocity of the observer and the velocity of the source.

Is That a Fact!◆ The longest recorded distance traveled by any audible

sound in air is about 4,600 km. The volcanic explo-sion on the Indonesian island of Krakatau, in 1883, propelled a column of smoke and ash more than 80 km into the air. The explosion sounded like distant cannon fire to people in Australia, Singapore, and Rodriguez Island—4,600 km away in the Indian Ocean. Waves reached the Pacific coastline of Colombia 19 h later, and tsunamis were recorded in other parts of South America.

◆ Sound travels 1.7 km in about 5 s in air that is 20°C. Sound travels the same distance (1.7 km) in just over 1 s underwater and in only 0.3 s in steel.

21

Interactions of Sound WavesBat Sonar and Human Technology• Experiments conducted at Brown University found

that bat sonar can detect the difference between echoes just 2- to 3-millionths of a second apart. The best naval sonar could differentiate between echoes about 5- to 10-millionths of a second apart.

Is That a Fact!◆ Nikola Tesla, a Croatian inventor, once created a

human-made earthquake by making a steam-driven oscillator vibrate at the resonant frequency of the ground. Tesla had accurately determined the resonant frequency of the Earth! In a similar experiment, Tesla proved theories of seismic wave activity by sending waves of energy through the Earth. As these waves of energy returned, Tesla added electric current to them and thereby created a human-made bolt of lightning that measured 40 m. The accompanying thunder was heard for more than 35 km!

Sound QualityRecording Sound• The two basic methods of recording sound are analog

and digital recording. In analog recording, the record-ing medium varies continuously with the incoming signal. In digital recording, the signal is recorded as a rapid sequence of coded measurements.

Is That a Fact!◆ Notes on a musical scale are set by exact frequencies.

Although humans can hear frequencies as low as 20 Hz, the lowest frequency heard as a note is about 30 Hz. The highest frequency audible to humans is about 20,000 Hz. Middle C on the piano has a frequency of 263 Hz.

◆ Little was known about the science of sound until the 1600s. The Greeks were more interested in music than in the scientific aspects of sound. However, the Greek philosopher and mathematician Pythagoras (c. 580–500 BCE) discovered that doubling the frequency of a pitch produces a pitch one octave higher.

• Both methods preserve the varying voltage of the sound signal, but digital recording eliminates the hiss or electrical noise. Analog recordings can be improved by a noise reduction system, such as the Dolby®-system.

SciLinks is maintained by the National Science Teachers Association to provide you and your students with interesting, up-to-date links that will enrich your classroom presentation of the chapter.


Topic: What Is Sound?SciLinks code: HSM1663

Topic: The EarSciLinks code: HSM0440

Topic: Properties of SoundSciLinks code: HSM1233

Topic: Interactions of SoundWaves

SciLinks code: HSM0804

Topic: Sound QualitySciLinks code: HSM1427

Visit www.scilinks.org and enter the SciLinks code for more information about the topic listed.

For background information about teaching strategies and

issues, refer to the Professional Reference for Teachers.

Chapter 21 • Chapter Enrichment 597F

Standards Correlations

National Science Education Standards

The following codes indicate the National Science EducationStandards that correlate to this chapter. The full text of thestandards can be found at the front of the book.

Chapter OpenerSAI 1, 2

Section 1 What Is Sound?SAI 1, 2; SPSP 1; PS 3a

Section 2 Properties of SoundUCP 1, 3; SAI 1, 2; PS 3a

Section 3 Interactions of Sound WavesUCP 1; PS 3a

Section 4 Sound QualityUCP 5

Chapter LabSAI 1, 2

Chapter ReviewPS 3a

Science in ActionUCP 5; ST 2; SPSP 5

OverviewTell students that this chapterwill help them learn about thenature of sound. The chapterbegins with a description ofsound as longitudinal wavesmade by vibrations and carriedthrough a medium, such as air.Properties like speed, pitch, andamplitude are then discussed.Students will then learn aboutinteractions of sound waves,such as echoes, interference, andthe Doppler effect. Differencesin production of sound betweenmusical instruments and themeaning of the term soundquality will then be discussed.

Assessing PriorKnowledgeStudents should be familiarwith the following topics:

• particles

• energy

• waves

IdentifyingMisconceptionsMany students wrongly intuitthat sound cannot travelthrough solids and liquids andcan travel through a vacuumand space. They also maybelieve that sound can be pro-duced without any materials.Many students will also guessthat hitting an object harder willchange the pitch of the soundproduced.

598 Chapter 21 • The Nature of Sound

PRE-READINGPRE-READING

The Nature of Sound

About the

Look at these dolphins swimming swiftlyand silently through their watery world. Waita minute—swiftly? Yes. Silently? No way!Dolphins use sound—clicks, squeaks, andother noises—to communicate. Dolphins alsouse sound to locate their food by echolocationand to fi nd their way through murky water.

Concept Map Beforeyou read the chapter, cre-ate the graphic organizer

entitled “Concept Map” described in theStudy Skills section of the Appendix. Asyou read the chapter, fill in the conceptmap with detailsabout each type ofsound interaction.

SECTION

The properties and interactionsof sound waves affect whatone hears.

21

1 What Is Sound? . . . . . . . . . . . . 600

2 Properties of Sound. . . . . . . . . 606

3 Interactions ofSound Waves . . . . . . . . . . . . . . 612

4 Sound Quality. . . . . . . . . . . . . . 618

21

START-UPA Homemade GuitarIn this chapter, you will learn about sound. You can start by making your own guitar. It won’t sound as good as a real guitar, but it will help you explore the nature of sound.

Procedure1. Stretch a rubber band lengthwise around an

empty shoe box. Place the box hollow side up. Pluck the rubber band gently. Describe what you hear.

2. Stretch another rubber band of a different thickness around the box. Pluck both rubber bands. Describe the differences in the sounds.

3. Put a pencil across the center of the box and under the rubber bands, and pluck again. Compare this sound with the sound you heard before the pencil was used.

4. Move the pencil closer to one end of the shoe box. Pluck on both sides of the pencil. Describe the differences in the sounds you hear.

Analysis1. How did the thicknesses of the rubber bands

affect the sound?

2. In steps 3 and 4, you changed the length of the vibrating part of the rubber bands. What is the relationship between the vibrating length of the rubber band and the sound that you hear?

Chapter 21 • The Nature of Sound 599

START-UPSTART-UP vvM A T E R I A L S

FOR EACH GROUP• pencil• rubber band, thick• rubber band, thin• shoe box

Teacher’s Notes:1. Students should hear a sound

and see the rubber band vibrate.

2. Students should hear a higher pitch or note from the thin-ner rubber band. They might not use the words pitch ornote at this point, but they should be able to notice and describe the differences between the two sounds.

3. When the pencil is used, the pitch of the sound is higher.

4. A high pitch is produced by the short part of the rubber band, and a low pitch is pro-duced by the longer part of the rubber band.

Answers

1. The thicker the rubber band is, the lower the pitch.

2. The shorter the rubber band is, the higher the pitch.

Would You Believe . . . ?

The Nature of Sound CHAPTER STARTER

In 1271, the Italian explorer Marco Polobegan his historic journey to China withhis father and uncle. He was only 17years old. Though he didn’t know it atthe time, 24 years would pass before heand his companions would return hometo Venice, Italy.

Upon his return, Marco Polo wroteof the many incredible things he hadobserved while in Asia. One such thingwas the booming sand dunes of theAsian desert. Marco Polo wrote how thesands actually made noises, filling theair with sounds of music, drums, andweapons of war.

Although they were a mystery duringMarco Polo’s time, much has beenlearned about these booming sands. Forexample, they are most often found inthe middle of large deserts. The loud,low-pitched sounds—which have beencompared to foghorns, cannon fire, andmoaning—can last from a few secondsto 15 minutes and can be heard morethan 10 km away! Booming sands havebeen discovered all over the world,including the United States.

Scientists have learned that the loudsounds are caused by avalanches of sandwithin a dune. As the top layers of sandslip over the layers below, vibrations are

produced that create the strange sounds.However, scientists are still not sure whythese sands make noise and other sandsdo not.

Although there is still much to learnabout booming sands, the nature of soundis well understood. In this chapter, youwill learn about sound, its properties, andhow sound waves interact to influenceyour life.

Marco Polo

Sand Mountain, in Nevada, makes low droning sounds.


Chapter Starter TransparencyUse this transparency to help students begin thinking about the nature of sound.

CHAPTER RESOURCESTechnology

Transparencies• Chapter Starter Transparency

Student Edition on CD-ROM

Guided Reading Audio CD• English or Spanish

Classroom Videos• Brain Food Video Quiz

Workbooks

Science Puzzlers, Twisters & Teasers• The Nature of Sound g

READINGSKILLS

READING STRATEGY

What Is Sound?You are in a restaurant, and without warning, you hear a loudcrash. A waiter dropped a tray of dishes. What a mess! Butwhy did dropping the dishes make such a loud sound?

In this section, you’ll find out what causes sound and whatcharacteristics all sounds have in common.You’ll also learnhow your ears detect sound and how you can protect yourhearing.

Sound and VibrationsAs different as they are, all sounds have some things incommon. One characteristic of sound is that it is created byvibrations. A vibration is the complete back-and-forth motionof an object. Figure 1 shows one way sound is made byvibrations.

Electrical signals make the speaker vibrate. As thespeaker cone moves forward, it pushes the air particlesin front of it closer together, creating a region of higherdensity and pressure called a compression.

a

As the speaker cone moves backward, air particles closeto the cone become less crowded, creating a region oflower density and pressure called a rarefaction.

b

For each vibration, a compression and a rarefaction areformed. As the compressions and rarefactions travel awayfrom the speaker, sound is transmitted through the air.

c

Sounds from a Stereo SpeakerFigure 1

1What You Will Learn

Describe how vibrations causesound.Explain how sound is transmittedthrough a medium.Explain how the human ear works,and identify its parts.Identify ways to protect yourhearing.

Vocabularysound wavemedium

Prediction Guide Before reading thissection, predict whether each of thefollowing statements is true or false:

• Sound waves are made byvibrations.

• Sound waves push air particlesalong until they reach your ear.

1

OverviewThis section introduces soundand how it is produced. Studentslearn how sound waves traveland how the human ear works.

BellringerTell students that if they’ve everbeen near a large fireworks dis-play, they may have felt thesound of the explosions. Askthem to think of other timesthey might feel sound and todescribe them in their sciencejournal.

Demonstration --------------gVibrations of Stereo SpeakersSet up a stereo system withspeakers—these must havewoofers that reproduce low-frequency sounds—in the class-room, and remove the outercover of the speakers. Play musicthat has a strong bass beat orbass notes. Students will be ableto see the woofers vibrating withthe bass sounds. Challenge themto explain why the vibrationsof the woofers can be seen butthe vibrations of the tweetersare almost imperceptible.l Auditory/Visual

CHAPTER RESOURCES

Chapter Resource File

CRF • Lesson Plan • Directed Reading Ab • Directed Reading Bs

Technology

Transparencies• P85 Sounds from a Stereo Speaker

Workbooks

Interactive Textbook Struggling Readers Struggling Readers


Good Vibrations

1. Gently strike a tuning fork on a rubber eraser. Watch theprongs, and listen for a sound. Describe what you see andwhat you hear.

2. Lightly touch the fork with your fingers. What do you feel?3. Grasp the prongs of the fork firmly with your hand. What

happens to the sound?4. Strike the tuning fork on the eraser again, and dip the prongs

in a cup of water. Describe what happens to the water.5. Record your observations.

Sound WavesLongitudinal (LAHN juh TOOD’n uhl) waves are made ofcompressions and rarefactions. A sound wavesound wave is a longitudinalwave caused by vibrations and carried through a substance.The particles of the substance, such as air particles, vibrateback and forth along the path that the sound wave travels.Sound is transmitted through the vibrations and collisionsof the particles. Because the particles vibrate back and forthalong the paths that sound travels, sound travels as longitu-dinal waves.

Sound waves travel in all directions away from their source,as shown in Figure 2. However, air or other matter does nottravel with the sound waves. The particles of air only vibrateback and forth. If air did travel with sound, wind gusts frommusic speakers would blow you over at a school dance!

✓✓Reading Check What do sound waves consist of? (See theAppendix for answers to Reading Checks.)

sound wavesound wave a longitudinal wavethat is caused by vibrations and thattravels through a material medium

Figure 2 You can’t actuallysee sound waves, but they canbe represented by spheres thatspread out in all directions.

Compression Rarefaction

vv---------------------------------------------------g

Sounds in Your World Havestudents write in their sciencejournal all the different soundsthey hear during a typical day.Have students describe whichsounds they enjoy and whichare unpleasant to the ear andwhy. l Intrapersonal

StrategiesStrategiesINCLUSIONINCLUSION

• Behavior Control Issues• Visually Impaired• Hearing ImpairedMake sure students under-stand the word vibration.Borrow a drum from theband room. Place the drumon its side. Have two or threestudents hold their hands onthe bottom of the drum.Firmly hit the top of thedrum several times. Ask stu-dents if they can feel thevibrations. Repeat with stu-dents’ hands at the edge. Askstudents if they can feel thehit any more “loudly” whentheir hands are on the topof the drum.l Kinesthetic ee

Answer to Reading Check

Sound waves consist of longitudinalwaves carried through a medium.

M A T E R I A L SFOR EACH GROUP

• eraser, rubber• plastic cup of water, small• tuning fork

Safety Caution: Remind students thatthe tuning forks should not touch theireyes or eyeglasses.

Answers

1. Students should hear a faint sound and theymay or may not see the tuning fork vibrate,depending on how hard the fork was struck.

2. Students should feel the prongs vibrate.3. The sound will immediately stop.4. The vibrations of the prongs will create

waves in the water in the cup.

Section 1 • What Is Sound? 601

Sound and MediaAnother characteristic of sound is that all sound waves require a medium (plural, media). A medium is a substance through which a wave can travel. Most of the sounds that you hear travel through air at least part of the time. But sound waves can also travel through other materials, such as water, glass, and metal.

In a vacuum, however, there are no particles to vibrate. So, no sound can be made in a vacuum. This fact helps to explain the effect described in Figure 3. Sound must travel through air or some other medium to reach your ears and be detected.

✓Reading Check What does sound need in order to travel?

How You Detect SoundImagine that you are watching a suspenseful movie. Just before a door is opened, the background music becomes louder. You know that there is something scary behind that door! Now, imagine watching the same scene without the sound. You would have more difficulty figuring out what’s going on if there were no sound.

Figure 4 shows how your ears change sound waves into electrical signals that allow you to hear. First, the outer ear collects sound waves. The vibrations then go to your middle ear. Very small organs increase the size of the vibrations here. These vibrations are then picked up by organs in your inner ear. Your inner ear changes vibrations into electrical signals that your brain interprets as sound.

medium a physical environment in which phenomena occur

Figure 3 Tubing is connected to a pump that is removing air from the jar. As the air is removed, the ringing alarm clock sounds quieter and quieter.

Vocal Sounds The vibrations that produce your voice are made inside your throat. When you speak, laugh, or sing, your lungs force air up your wind-pipe, causing your vocal cords to vibrate.

Do some research, and find out what role different parts of your throat and mouth play in making vocal sounds. Make a poster in which you show the different parts, and explain the role they play in shaping sound waves.


Discussion ----------------------------------g

Sound in Space? Some science fiction movies are full of scenes of roaring spacecraft, loud drill-ing on asteroids, or deafening explosions during fictional space battles. Discuss with students why these movies are not scien-tifically accurate. l Logical

GroupGroup vv -------g

Sound Samples Have groups of students search the school and grounds to record a variety of sounds. If possible, use a tape recorder or video camera. Instruct them to find the following sounds:

• high-pitched sound

• sound from above or overhead

• repeating sound

• sound that would startle

• irritating sound

• sound made by an animal

• sound made by wind

• sound made by something moving

Students should record what the sound is and where it was made. Compare and discuss what different groups found. l Interpersonal cc


Sound needs a medium in order to travel.

h-----------------------------g

Hearing Aids Because so many young people listen to very loud music through headphones, one of the next major indus-tries may be the manufacturing of hearing aids. Have students research the different kinds of hearing aids available, how they work, and their costs. l Logical

A cricket hears through its front legs and produces a series of chirps, or trills, by rubbing its two front wings together. And the pistol shrimp makes a sound much like a gunshot by snapping shut its enlarged claw.

Pinna

Ear canal

HammerAnvil

Stirrup

Eardrum

Cochlea

Sound waves vibrate the eardrum—alightly stretched membrane that isthe entrance to the middle ear.

The vibration of theeardrum makes thehammer vibrate, which,in turn, makes the anviland stirrup vibrate.

The stirrup vibrates theoval window—the entranceto the inner ear.

The vibrations of the ovalwindow create waves in theliquid inside the cochlea.

Movement ofthe liquid causestiny hair cells in-side the cochleato bend.

The bendingof the hair cellsstimulates nerves,which sendelectrical signalsto the brain.

In the middle ear, threebones—the hammer, anvil,and stirrup—act as leversto increase the size ofthe vibrations.

In the inner ear, vibra-tions created by sound arechanged into electrical signalsfor the brain to interpret.

b ca The outer ear acts as a funnel forsound waves. The pinna collectssound waves and directs them intothe ear canal.

1

2

3 4

56

How the Human Ear WorksFigure 4

CONNECTION toCONNECTION toLife Science -----------------------------------g

Vocal Cords and the LarynxThe vocal cords are located inthe throat in an organ called thelarynx. Besides producing sound,the larynx controls the flow ofair during breathing. The vocalcords are located in the center ofthe larynx. They are made ofthin strips of muscle. They forma V-shaped opening in the air-way. Other small muscles stretchand loosen the vocal cords toproduce different sounds as theair moves across them.

The inner ear contains the organs thatare responsible for maintaining balance.These organs are located in a hollowregion called the vestibule. Therefore,the sense of balance is sometimesreferred to as the vestibular sense.

CHAPTER RESOURCESTechnology

Transparencies• P86 How the Human Ear Works

SUPPORT FOR

English LanguageLearnersParts of the Ear Havestudents demonstrate compre-hension of the informationabout the parts of the ear byparaphrasing the text afterthey have read the diagram.Have students copy the dia-gram into their science jour-nal and rewrite the labels intheir own words. In a discus-sion setting, ask the followingquestions:What is the function (job)of the outer ear? (to collectsound waves and direct theminto the ear canal)What is the function (job) ofthe bones in the middle ear?(The three bones act as leversto increase the size of thevibrations.)What is the job of the innerear? (to convert vibrationsinto electric signals for thebrain to interpret)Check journals for accuracyand language usage, and havestudents make correctionsif necessary.l Visual/Verbal/Logical


Making Sound Versus Hearing SoundHave you heard this riddle? If a tree falls in the forest and no one is around to hear it, does the tree make a sound? Think about the situation pictured in Figure 5. When a tree falls and hits the ground, the tree and the ground vibrate. These vibrations make compressions and rarefactions in the surround-ing air. So, there would be a sound!

Making sound is separate from detecting sound. The fact that no one heard the tree fall doesn’t mean that there wasn’t a sound. A sound was made—it just wasn’t heard.

Hearing Loss and DeafnessThe many parts of the ear must work together for you to hear sounds. If any part of the ear is damaged or does not work properly, hearing loss or deafness may result.

One of the most common types of hearing loss is called tinnitus (ti NIET us), which results from long-term exposure to loud sounds. Loud sounds can cause damage to the hair cells and nerve endings in the cochlea. Once these hairs are damaged, they do not grow back. Damage to the cochlea or any other part of the inner ear usually results in permanent hearing loss.

People who have tinnitus often say they have a ringing in their ears. They also have trouble understanding other people and hearing the difference between words that sound alike. Tinnitus can affect people of any age. Fortunately, tinnitus can be prevented.

✓Reading Check What causes tinnitus?

Figure 5 Sound is made whether or not anyone is around to hear it.

For another activity related to this chapter, go to go.hrw.com and type in the keyword HP5SNDW.



Tinnitus is caused by long-term exposure to loud sounds.

Reteaching -------------------------------------bRetracing the Process of Sound and Hearing Ask students what the first step is in sound produc-tion. (a vibration) Have a student draw a very simple sketch of this on the board. Then, ask students what happens to the sound. (Sound waves [longitudinal waves] are carried through a medium.) Have another student draw a very simple sketch of this pro-cess on the board. Then, ask students what happens to the sound once it reaches your ear. (It is funneled by the outer ear, magnified by the middle ear, and changed into electrical signals by the inner ear.) Have another stu-dent draw a sketch of this pro-cess on the board. l Visual

Quiz ---------------------------------------------------------------------g

1. Name the three bones in the ear that act as levers. (hammer, anvil, stirrup)

2. What is necessary for sound to travel from its source to a listener? (a medium through which the sound waves can travel)

Alternative Assessment ---------------------------g

Hearing Problem Have stu-dents write letters to a fictional boss explaining that they are having a hearing problem at work. They should explain the problem and what corrections could be made in the workplace for the benefit of everyone who works there. l Verbal

Is That a Fact!Imagine the sound that is created when a giant sequoia falls! The most massive living organisms in the world are giant sequoia trees, which can grow to more than 85 m tall and can be more than 9 m in diameter at the base. Scientists estimate that some of the largest giant sequoias can have masses up to 2,500 t. Some of the oldest giant sequoias are more than 3,000 years old.

For a variety of links related to this chapter, go to www.scilinks.org

SummarySummary

Review

Protecting Your HearingShort exposures to sounds that are loud enough to be painful can cause hearing loss. Your hearing can also be damaged by loud sounds that are not quite painful, if you are exposed to them for long periods of time. There are some simple things you can do to protect your hearing. Loud sounds can be blocked out by earplugs. You can listen at a lower volume when you are using headphones, as in Figure 6. You can also move away from loud sounds. If you are near a speaker playing loud music, just move away from it. When you double the distance between yourself and a loud sound, the sound’s intensity to your ears will be one-fourth of what it was before.

Figure 6 Turning your radio down can help prevent hearing loss, especially when you use headphones.

• All sounds are generated by vibrations.

• Sounds travel as longi-tudinal waves consisting of compressions and rarefactions.

• Sound waves travel in all directions away from their source.

• Sound waves require a medium through which to travel. Sound cannot travel in a vacuum.

• Your ears convert sound into electrical impulses that are sent to your brain.

• Exposure to loud sounds can cause hearing damage.

• Using earplugs and lowering the volume of sounds can preventhearing damage.

Using Key Terms

1. Use the following terms in the same sentence: sound wave and medium.

Understanding Key Ideas

2. Sound travels as

a. transverse waves.b. longitudinal waves.c. shock waves.d. airwaves.

3. Which part of the ear increases the size of the vibrations of sound waves entering the ear?

a. outer earb. ear canalc. middle eard. inner ear

4. Name two ways of protecting your hearing.

Critical Thinking

5. Analyzing Processes Explainwhy a person at a rock concert will not feel gusts of wind coming out of the speakers.

6. Analyzing Ideas If a meteorite crashed on the moon, would you be able to hear it on Earth? Why, or why not?

7. Identifying Relationships Recall the breaking dishes mentioned at the beginning of this section. Why was the sound that they made so loud?

Interpreting Graphics

Use the diagram of a wave below to answer the questions that follow.

8. What kind of wave is this?

9. Draw a sketch of the diagram on a separate sheet of paper, and label the compressions and rarefactions.

10. How do vibrations make these kinds of waves?

Topic: The Ear; What Is Sound?SciLinks code: HSM0440; HSM1663


Answers to Section Review

1. Sample answer: A sound wave is carried through a medium by longitudinal waves.

2. b3. c4. wearing ear protection

devices and keeping a distance between your ears and loud sounds

5. All sounds are carried by longitudinal waves: In a wave, the particles themselves do not move forward with the wave.

6. no; There is no medium between the moon and Earth to carry sound waves.

7. The breaking of dishes involves a high energy of vibra-tions, so the sound is loud.

8. a longitudinal wave9. Diagrams should label the

areas dense with particles as “compressions,” and sparse areas as “rarefactions.”

10. The back-and-forth motion of a vibrating object forms com-pressions and rarefactions in the air around it.

CHAPTER RESOURCES


• Section Quiz g• Section Review g• Vocabulary and Section Summary g• SciLinks Activity g• Datasheet for Quick Lab

CRF

READING STRATEGY

Properties of SoundImagine that you are swimming in a neighborhood pool. Youcan hear the high, loud laughter of small children and the softsplashing of the waves at the edge of the pool.

Why are some sounds loud, soft, high, or low? The differencesbetween sounds depend on the properties of the sound waves.In this section, you will learn about properties of sound.

The Speed of SoundSuppose you are standing at one end of a pool and two peoplefrom the opposite end of the pool yell at the same time. You wouldhear their voices at the same time. The reason is that the speedof sound depends only on the medium in which the sound istraveling. So, you would hear them at the same time—even ifone person yelled louder!

How the Speed of Sound Can ChangeTable 1 shows how the speed of sound varies in different media.Sound travels quickly through air, but it travels even faster inliquids and even faster in solids.

Temperature also affects the speed of sound. In general, thecooler the medium is, the slower the speed of sound. Particlesof cool materials move more slowly and transmit energy moreslowly than particles do in warmer materials. In 1947, pilotChuck Yeager became the first person to travel faster than thespeed of sound. Yeager flew the airplane shown in Figure 1 at293 m/s (about 480 mi/h) at 12,000 m above sea level. At thataltitude, the temperature of the air is so low that the speedof sound is only 290 m/s.

2

Figure 1 The X-1 airplane wasthe first vehicle to move fasterthan the speed of sound.

Table 1 Speed of Soundin Different Media

Medium Speed (m/s)

Air (0°C) 331

Air (20°C) 343

Air (100°C) 366

Water (20°C) 1,482

Steel (20°C) 5,200

What You Will Learn

Compare the speed of sound indifferent media.Explain how frequency and pitchare related.Describe the Doppler effect, and giveexamples of it.Explain how amplitude and loudnessare related.Describe how amplitude andfrequency can be “seen” on anoscilloscope.

Vocabularypitch loudnessDoppler effect decibel

Reading Organizer As you readthis section, create an outline of thesection. Use the headings from thesection in your outline.

2

OverviewIn this section, students learnabout properties of sound, whataffects the speed of sound, andhow pitch and frequency arerelated. Students also learnabout the Doppler effect andhow volume and amplitude arerelated.

BellringerAsk students the followingquestion:

You are the commander of aspace station located about half-way between Earth and themoon. You are in the CommandCenter, and your chief of secu-rity tells you that sensors havejust de tected an explosion61.054 km from the station.How long will it be before youhear the sound of the explosion?(You won’t hear it. Sound waves willnot travel in the vacuum of space.)

Is That a Fact!In some western movies, a characterwould be shown put ting an ear to thehard ground to find out if someone wascoming. This technique actually worksbecause sound travels faster and withless loss of energy through the groundthan through air.

CHAPTER RESOURCES



Technology

Transparencies • Bellringer

• P87 Frequency and Pitch• P88 The Doppler Effect

Workbooks



Pitch and FrequencyHow low or high a sound seems to be is the pitch of that sound. The frequency of a wave is the number of crests or troughs that are made in a given time. The pitch of a sound is related to the frequency of the sound wave, as shown in Figure 2. Frequency is expressed in hertz (Hz), where 1 Hz � 1 wave per second. For example, the lowest note on a piano is about 40 Hz. The screech of a bat is 10,000 Hz or higher.

✓Reading Check What is frequency? (See the Appendix for answers to Reading Checks.)

Frequency and HearingIf you see someone blow a dog whistle, the whistle seems silent to you. The reason is that the frequency of the sound wave is out of the range of human hearing. But the dog hears the whistle and comes running! Table 2 compares the range of frequencies that humans and animals can hear. Sounds that have a frequency too high for people to hear are called ultrasonic.

pitch a measure of how high or low a sound is perceived to be, depending on the frequency of the sound wave

High frequency � high pitch

Low frequency � low pitch

Frequency and PitchFigure 2

The Speed of SoundThe speed of sound depends on the medium through which sound is traveling and the medium’s temperature. Sound travels at 343 m/s through air at a temperature of 20°C. How far will sound travel in 20°C air in 5 s?

The speed of sound in steel at 20°C is 5,200 m/s. How far can sound travel in 5 s through steel at 20°C?

Table 2 Frequencies Heard by Different Animals

Animal Frequency range (Hz)

Bat 2,000 to 110,000

Porpoise 75 to 150,000

Cat 45 to 64,000

Beluga whale 1,000 to 123,000

Elephant 16 to 12,000

Human 20 to 20,000

Dog 67 to 45,000

vv---------------------------------------------------g

M A T E R I A L SFOR EACH PAIR OFSTUDENTS• cups, paper (2)• string, several types, 6 m each

Paper Cup Phones Have stu-dents punch a hole in the bot-tom of each cup, insert one end of the string into each cup, and tie a knot in the string. Have one student from each pair talk quietly into the cup while the other listens through the second cup. Have each pair experiment with the types of string, the ten-sion of the strings, and lengths of the strings to see which com-bination works best. l Auditory

CONNECTIONCONNECTION vvMath ----------------------------------------------------------------------------g

Speed of Sound in Steel Ask students the following ques-tion: “The temperature is 20°C. You are standing next to a rail-ing located in a national park. The railing is 7,700 m long and is made of steel. Your friend is at the other end of the railing, and she hits the railing with a hammer. How long will it take for the sound to get to you through the railing: less than 1 s, between 1 s and 2 s, or more than 2 s? Explain your answer.” (between 1 s and 2 s; Sound trav-els 5,200 m through steel in 1 s. Therefore, sound will take between 1 s and 2 s to travel through the 7,700 m rail.) l Logical

Answers to Math Practice

air: 343 m/s � 5 s � 1,715 m;steel: 5,200 m/s � 5 s � 26,000 m


Frequency is the number of crests or troughs made in a given time.

Is That a Fact!Studies now show that regions of hair cells within the inner ear are actually “tuned” to specific frequencies. Because of their differences in size and shape, hair cells have a specific resonance at which they vibrate. Thus, certain fre-quencies will activate some hair cells but not others.

Section 2 • Properties of Sound 607

The Doppler EffectHave you ever been passed by a car with its horn honking?If so, you probably noticed the sudden change in pitch—sortof an EEEEEOOoooowwn sound—as the car went past you. Thepitch you heard was higher as the car moved toward youthan it was after the car passed. This higher pitch was a resultof the Doppler effect. For sound waves, the Doppler effect isthe apparent change in the frequency of a sound caused bythe motion of either the listener or the source of the sound.Figure 3 shows how the Doppler effect works.

In a moving sound source, such as a car with its hornhonking, sound waves that are moving forward are going thesame direction the car is moving. As a result, the compressionsand rarefactions of the sound wave will be closer togetherthan they would be if the sound source was not moving. Toa person in front of the car, the frequency and pitch of thesound seem high. After the car passes, it is moving in theopposite direction that the sound waves are moving. To aperson behind the car, the frequency and pitch of the soundseem low. The driver always hears the same pitch because thedriver is moving with the car.

Doppler effect an observedchange in the frequency of awave when the source orobserver is moving

A car with its horn honking movestoward the sound waves going in thesame direction. A person in front of the carhears sound waves that are closer together.

The car moves away from the sound wavesgoing in the opposite direction. A personbehind the car hears sound waves that arefarther apart and have a lower frequency.

ba

The Doppler EffectFigure 3

a b

vv------------------------------------------b

Doppler Diagram Have studentsuse colored pencils to draw adiagram showing the Dopplereffect. Have them include alistener, a vehicle, and linesdepicting sound waves. l Visual

CONNECTION toCONNECTION toHistory --------------------------------------------------g

Doppler Effect The Doppler effect isnamed after the Austrian mathematicianChristian Doppler (1803–1853), who firstproposed it in 1842 in a paper describingthe colored light of double stars. In 1845,Doppler applied his theory to sound wavesand tested it with trumpet players on a

train. In 1929, astronomer Edwin Hubble(1889–1953) used Doppler’s theory to inter-pret his measurements and show that thefarther away from Earth a galaxy is, thefaster it is moving away from Earth and themore the light from that galaxy is “shifted”toward the red end of the spectrum.

SUPPORT FOR

English LanguageLearnersThe Doppler Effect inAction A demonstration willhelp students understand theDoppler effect. Find a noise-maker that produces a con-stant sound (a small buzzeror something similar). Attachthe noisemaker to the endof a string approximately 70cm to 90 cm long. (It may benecessary to do the demon-stration outside.) Let studentshear the noise from thenoisemaker. Stand away fromthe students and walls. Swingthe noisemaker by the stringin a wide circle over yourhead. Ask students to describewhat they hear in terms ofthe Doppler effect. (When thenoisemaker is coming towardthem, they will hear a higherpitch because the soundwaves are closer together.When it is moving awayfrom them they will hear alower pitch because the soundwaves are farther apart.) Callon students to ensure full par-ticipation.l Visual/Auditory


Loudness and AmplitudeIf you gently tap a drum, you will hear a soft rumbling. But if you strike the drum with a large force, you will hear a much louder sound! By changing the force you use to strike the drum, you change the loudness of the sound that is created. Loudness is a measure of how well a sound can be heard.

Energy and VibrationLook at Figure 4. The harder you strike a drum, the louder the boom. As you strike the drum harder, you transfer more energy to the drum. The drum moves with a larger vibration and transfers more energy to the air around it. This increase in energy causes air particles to vibrate farther from their rest positions.

Increasing AmplitudeWhen you strike a drum harder, you are increasing the amplitude of the sound waves being made. The amplitude of a wave is the largest distance the particles in a wave vibrate from their rest positions. The larger the amplitude, the louder the sound. And the smaller the amplitude, the softer the sound. One way to increase the loudness of a sound is to use an amplifier, shown in Figure 5. An amplifier receives sound signals in the form of electric current. The amplifier then increases the energy and makes the sound louder.

✓Reading Check What is the relationship between the amplitude

of a sound and its energy of vibration?

loudness the extent to which a sound can be heard

Figure 5 An amplifier increases the amplitude of the sound generated by an electric guitar.

Figure 4 When a drum is struck hard, it vibrates with a lot of energy, making a loud sound.

Sounding Board

1. With one hand, hold a ruler on your desk sothat one end of it hangs over the edge.

2. With your other hand, pull the free end of the ruler up a few centimeters, and let go.

3. Try pulling the ruler up different distances. How does the distance affect the sounds you hear? What property of the sound wave are you changing?

4. Change the length of the part that hangs over the edge. What property of the sound wave is affected? Record your answers and observations.

CONNECTION toCONNECTION toLife Science -----------------------------------g

A Very Loud Bird The loudest bird in North America is the whooping crane. Its call can be heard from about 5 km away.


The amplitude of a sound increases as the energy of the vibrations that caused the sound increases.

CONNECTION toCONNECTION toReal World --------------------------------------------g

Loud Music Listening to loud music and attending loud con-certs can be harmful to your hearing. Loudness is expressed in decibels (dB). Long-term exposure to sounds above 85 dB is considered hazardous to your hearing. Sounds louder than 85 dB take less time to cause hear-ing damage. Music concerts are often 110 dB or louder, so the potential for hearing damage is very real.

Safety Caution: Remind students to wear safety goggles when doing this lab.

Teacher’s Note: Any stiff wooden or plastic ruler will work for this lab.

Answers

3. The farther up they pull the ruler, the louder the sound will be. Amplitude is changing.

4. Changing the length of the ruler hanging off the edge changes the frequency of the sound wave. The shorter the length of the ruler hanging off the edge of the table, the higher the pitch will be.


Measuring LoudnessThe most common unit used to express loudness is thedecibeldecibel (dB). The softest sounds an average human can hearare at a level of 0 dB. Sounds that are at 120 dB or highercan be painful. Table 3 shows some common sounds and theirdecibel levels.

“Seeing” Amplitude and FrequencySound waves are invisible. However, technology can provide away to “see” sound waves. A device called an oscilloscope (uhSIL uh SKOHP) can graph representations of sound waves, asshown in Figure 6. Notice that the graphs look like transversewaves instead of longitudinal waves.

✓✓Reading Check What does an oscilloscope do?

decibeldecibel the most commonunit used to measure loudness(symbol, dB)

The graph on the right has a larger amplitude thanthe graph on the left. So, the sound representedon the right is louder than the one representedon the left.

The graph on the right has a lower frequency thanthe one on the left. So, the sound representedon the right has a lower pitch than the one repre-sented on the left.

Decibel LevelsWith an adult,

listen for the normal soundsthat happen around yourhouse. In your sciencejournal, write down somesounds and what you thinktheir decibel levels mightbe. Then, move closer to thesource of each sound, andwrite what you think the newdecibel level of each is.

”Seeing” SoundsFigure 6

Table 3 Decibel Levels of Common Sounds

Decibel level Sound

0 the softest sounds you can hear

20 whisper

25 purring cat

60 normal conversation

80 lawn mower, vacuum cleaner, truck traffic

100 chain saw, snowmobile

115 sandblaster, loud rock concert, automobile horn

120 threshold of pain

140 jet engine 30 m away

200 rocket engine 50 m away

WRITINGSKILL


An oscilloscope turns sounds into electricalsignals and graphs the signals.

Reteaching -------------------------------------bSound Relationships Write thewords frequency and amplitudein one line on the board, andloudness and pitch on the nextline. Ask students to match eachterm with its counterpart. Then,ask students what kind ofrelationship is involved in eachpair. (Frequency is related to pitch,and amplitude is related to loud-ness. Both are direct relationships,meaning if one increases, the otheralso increases.) l Visual/Logical

Quiz ---------------------------------------------------------------------g

1. Name three properties ofsound. (speed, pitch, andloudness)

2. Explain how a person canobserve the Doppler effect.(When the source of a loud noiseis moving toward or away froma listener, the sound appears tochange pitch because the soundwaves are moving closer togetheror farther apart relative to thelistener’s position.)

AlternativeAssessment ---------------------------g

Concept Mapping Have stu-dents create a concept mapshowing the properties of sound.Concept maps should includethe vocabulary terms from thissection and examples illustratingthe terms. l Visual




SummarySummary

Review

From Sound to Electrical SignalAn oscilloscope is shown in Figure 7. A micro-phone is attached to the oscilloscope and changes a sound wave into an electrical signal. The electri-cal signal is graphed on the screen in the form of a wave. The graph shows the sound as if it were a transverse wave. So, the sound’s amplitude and frequency are easier to see. The highest points (crests) of these waves represent compressions, and the lowest points (troughs) represent rarefactions. By looking at the displays on the oscilloscope, you can quickly see the differences in amplitude and frequency of different sound waves.

Figure 7 An oscilloscope can be used to represent sounds.

• The speed of sound depends on the medium and the temperature.

• The pitch of a sound becomes higher as the frequency of the sound wave becomes higher. Frequency is expressed in units of Hertz (Hz), which is equivalent to waves per second.

• The Doppler effect is the apparent change in frequency of a sound caused by the motion of either the listener or the source of the sound.

• Loudness increases with the amplitude of the sound. Loudness is expressed in decibels.

• The amplitude and fre-quency of a sound can be measured electroni-cally by an oscilloscope.

Using Key Terms

1. In your own words, write a definition for the term pitch.

2. Use the following terms in the same sentence: loudnessand decibel.


3. At the same temperature, in which medium does sound travel fastest?

a. airb. liquidc. solidd. It travels at the same speed

through all media.

4. In general, how does the temperature of a medium affect the speed of sound through that medium?

5. What property of waves affects the pitch of a sound?

6. How does an oscilloscope allow sound waves to be “seen”?

Math Skills

7. You see a distant flash of light-ning, and then you hear a thun-derclap 2 s later. The sound of the thunder moves at 343 m/s. How far away was the lightning?

8. In water that is near 0°C, a submarine sends out a sonar sig-nal (a sound wave). The signal travels 1500 m/s and reaches an underwater mountain in 4 s. How far away is the mountain?

Critical Thinking

9. Analyzing Processes Will a listener notice the Doppler effect if both the listener and the source of the sound are traveling toward each other? Explain your answer.

10. Predicting Consequences A drum is struck gently, then is struck harder. What will be the difference in the amplitude of the sounds made? What will be the difference in the frequency of the sounds made?

Topic: Properties of SoundSciLinks code: HSM1233


1. Sample answer: how low or high a sound seems, which depends on the frequency of the sound waves

2. Loudness is expressed sci-entifically in units of decibels.

3. c4. Sound tends to travel fast-

est in higher-temperature media.

5. Pitch is determined by the frequency of sound waves.

6. An oscilloscope changes sound waves into electronic signals, which are represented on a screen.

7. 343 m/s � 2 s � 686 m8. 1,500 m/s � 4 s � 6,000 m9. yes; The sound waves in

front of the source will become closer together as the source moves forward. Also, the lis-tener will “meet” the sound waves more rapidly by moving toward the source. The move-ments of both the source and the listener will make the pitch of the sound higher.

10. The amplitude of the sound will be higher when the drum is struck harder. The frequency will not change.

CHAPTER RESOURCES


• Section Quiz g• Section Review g• Vocabulary and Section Summary g• Reinforcement Worksheet b• Datasheet for Quick Lab

CRF

READING STRATEGY

Interactions of Sound WavesHave you ever heard of a sea canary? It’s not a bird! It’s a whale! Beluga whales are sometimes called sea canaries because of the many different sounds they make.

Dolphins, beluga whales, and many other animals that livein the sea use sound to communicate. Beluga whales also relyon reflected sound waves to find fish, crabs, and shrimp toeat. In this section, you will learn about reflection and otherinteractions of sound waves. You will also learn how bats,dolphins, and whales use sound to find food.

Reflection of Sound WavesReflection is the bouncing back of a wave after it strikes abarrier. You’re probably already familiar with a reflected soundwave, otherwise known as an echo.echo. The strength of a reflectedsound wave depends on the reflecting surface. Sound wavesreflect best off smooth, hard surfaces. Look at Figure 1. A shoutin an empty gymnasium can produce an echo, but a shout inan auditorium usually does not.

The difference is that the walls of an auditorium areusually designed so that they absorb sound. If sound waveshit a flat, hard surface, they will reflect back. Reflection ofsound waves doesn’t matter much in a gymnasium. Butyou don’t want to hear echoes while listening to a musicalperformance!

echoecho a reflected sound wave

Sound waves easily reflect off the smooth, hard walls of a gymnasium. For this reason, you hear an echo.

In well-designed auditoriums, echoes are reduced by soft materials that absorb sound waves and by irregular shapes that scatter sound waves.

3

Sound Reflection and AbsorptionFigure 1

What You Will Learn

Explain how echoes are made,and describe their use inlocating objects.List examples of constructiveand destructive interference ofsound waves.Explain what resonance is.

Vocabularyecho sonic boomecholocation standing waveinterference resonance

Paired Summarizing Read thissection silently. In pairs, take turnssummarizing the material. Stop todiscuss ideas that seem confusing.

3

OverviewIn this section students learnabout reflection and echoloca-tion. They also learn about con-structive and destructive waveinterference and resonance.

BellringerPut these questions on theboard:

• On an oscilloscope, does awave with a larger amplitude(greater crests and troughs)indicate louder sound orhigher pitch? (louder sound)

• As frequency increases, doespitch get higher or lower?(higher)

• What is the speed of sounddependent on? (Sample answer:the medium and its temperature)

• What do you think happenswhen two sound waves inter-act with each other? (Answersmay vary.)

Demonstration --------------gSound Waves in WaterFill a shallow pan with water.Let it sit until the surface of thewater becomes still. Tap a tuningfork, and touch the fork to thesurface of the water. Ask stu-dents to explain in their sciencejournal why the water moves.l Visual

Is That a Fact!According to Greek mythology, echoesoriginated when the angry goddess Heraplaced a curse on the wood nymphEcho that caused her to repeat whateverwas said to her.

CHAPTER RESOURCES



Technology

Transparencies • Bellringer • LINK TOLINK TO EARTH SCIENCEEARTH SCIENCE E48 How Sonar Works

• P89 Echolocation• P90 How Sonar Works

Workbooks



EcholocationBeluga whales use echoes to find food. The use of reflected sound waves to find objects is called echolocation. Other animals—such as dolphins, bats, and some kinds of birds—also use echolocation to hunt food and to find objects in their paths. Figure 2 shows how echolocation works. Animals that use echolocation can tell how far away something is based on how long it takes sound waves to echo back to their ears. Some animals, such as bats, also make use of the Doppler effect to tell if another moving object, such as an insect, is moving toward it or away from it.

✓Reading Check How is echolocation useful to some animals? (See the Appendix for answers to Reading Checks.)

Echolocation TechnologyPeople use echoes to locate objects underwater by using sonar (which stands for sound navigation andranging). Sonar is a type of electronic echolocation. Figure 3 shows how sonar works. Ultrasonic waves are used because their short wavelengths give more details about the objects they reflect off. Sonar can also help navigators on ships avoid icebergs and can help oceanographers map the ocean floor.

Figure 2 Bats use echolocation to navigate around barriers and to find insects to eat.

When the sound waves strike an object, the waves are reflected back to the bat. The time it takes for the echoes to reach the bat lets the bat know how far away the obstacle is.

The bat can detect an insect flying toward it because of the Doppler effect. The echo will have a higher frequency than that of the original sound wave.

Figure 3 A fish finder sends ultrasonic waves down into the water. The time it takes for the echo to return helps determine the location of the fish.

Bats emit ultrasonic waves as they fly.

1

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echolocation the process of using reflected sound waves to find objects; used by animals such as bats

Section 3 • Interactions of Sound Waves 613

CONNECTIONCONNECTION vvLanguage Arts -------------------------g

The Power of Sound The power of sound is so strong that stories have been written about it. In Homer’s epic poem TheOdyssey, the war hero Odysseus makes his journey home after the Trojan War. Odysseus and his crew sail near an island where beautiful women sing so sweetly that men are lured to their death. While his men put wax in their ears, Odysseus chooses to be lashed to the mast so that he can hear the beauti-ful music but not be lured onto the rocks. Have students write a story in which the plot depends on a sound. Students must include science concepts learned in this chapter. l Verbal

CONNECTION toCONNECTION toEarth Science ---------------------------g

Sonar in Oceanography Use the teaching transparency “How Sonar Works” to show students how scientists use sound waves to map the ocean floor.

StrategiesStrategiesINCLUSIONINCLUSION

• Gifted and Talented• Behavior Control IssuesMany students benefit from learning beyond the class-room walls. Have students hypothesize and then check whether or not sound waves reflect to create echoes in different school locations like the following: audi-torium, gym, classroom, cafeteria, music room, and inside a desk. Ask them to also check on other locations in their homes and local area. Have students present their findings in one joint presentation. l Interpersonal cc


Echolocation helps some animals find food.Is That a Fact!Dolphins use echolocation by emitting rapid, high-pitched clicks and listening for the returning echo. The closer a dolphin gets to an object, the faster the clicks return. As a dolphin moves its head side to side to scan, it detects both distance and shape. Dolphins can detect an object that is 2 cm in diameter more than 70 m away in open water.

UltrasonographyUltrasonography (UHL truh soh NAHG ruh fee)is a medical procedure that uses echoes to“see” inside a patient’s body without doingsurgery. A special device makes ultrasonic waveswith a frequency that can be from 1 million to 10million hertz, which reflect off the patient’sinternal organs. These echoes are then changed intoimages that can be seen on a television screen,as shown in Figure 4. Ultrasonography is used toexamine kidneys, gallbladders, and other organs. Itis also used to check the development of an unbornbaby in a mother’s body. Ultrasonic waves are lessharmful to human tissue than X rays are.

Interference of Sound WavesSound waves also interact through interference. Interferencehappens when two or more waves overlap. Figure 5 showshow two sound waves can combine by both constructive anddestructive interference.

Orchestras and bands make use of constructive interfer-ence when several instruments of the same kind play thesame notes. Interference of the sound waves causes thecombined amplitude to increase, resulting in a louder sound.But destructive interference may keep some members of theaudience from hearing the concert well. In certain places inan auditorium, sound waves reflecting off the walls interferedestructively with the sound waves from the stage.

✓Reading Check What are the two kinds of sound

wave interference?

Sound waves from two speakers producingsound of the same frequency combine byboth constructive and destructive interference.

Constructive InterferenceAs the compressions of one waveoverlap the compressions of anotherwave, the sound will be louderbecause the amplitude is increased.

Destructive InterferenceAs the compressions of one waveoverlap the rarefactions of anotherwave, the sound will be softerbecause the amplitude is decreased.

sonic boom the explosive soundheard when a shock wave from anobject traveling faster than the speedof sound reaches a person’s ears

interference the combination oftwo or more waves that results in asingle wave

Constructive and Destructive InterferenceFigure 5

Figure 4 Images created by ultrasonographyare fuzzy, but they are a safe way to seeinside a patient’s body.

CONNECTIONCONNECTION vvReal World ---------------------------------------------g

The sound transmission class(STC) rating tells how wellbuilding materials insulatesound. The higher the number,the more the material blockssound.

STC # What can be heard

25 Normal speech can beheard.

30 Loud speech can beheard.

35 Loud speech is audiblebut not intelligible.

42 Loud speech is audibleas a murmur.

45 A person must strain tohear loud speech.

48 Some loud speech isbarely audible.

50 Loud speech is inaudible.

Have students research what sortof building materials have theSTC ratings given above. Then,have students design a houseand use this rating system todetermine what building materialsto use. Ask them to explain whythey put the materials wherethey did. l Logical


Sound wave interference can beeither constructive or destructive.

Is That a Fact!Mach number is not a speed. It is theratio between the speed of an object,usually an airplane, and the speed ofsound in the medium in which the objectis traveling. A plane traveling at Mach 3.0is traveling at 3 times whatever the speedof sound is at the plane’s altitude.

SUPPORT FOR

English Language LearnersUltrasonography Students will benefitfrom seeing an ultrasound of an organor an unborn baby. Before you showthe ultrasound, describe what they willsee and ask them to predict how muchdetail they will be able to view. Presentthe ultrasound on an overhead projec-tor, and enlarge to show detail. Pointout features of the image. Ask, “Did yousee the details you expected to see? Wasanything in the picture different fromwhat you expected?”l Visual/Verbal


Interference and the Sound BarrierAs the source of a sound—such as a jet plane—gets close to the speed of sound, the sound waves in front of the jet plane get closer and closer together. The result is constructive interference. Figure 6 shows what happens as a jet plane reaches the speed of sound.

For the jet in Figure 6 to go faster than the speed of sound, the jet must overcome the pres-sure of the compressed sound waves. Figure 7shows what happens as soon as the jet reaches supersonic speeds—speeds faster than the speed of sound. At these speeds, the sound waves trail off behind the jet. At their outer edges, the sound waves combine by constructive interference to form a shock wave.

A sonic boom is the explosive sound heard when a shock wave reaches your ears. Sonic booms can be so loud that they can hurt your ears and break windows. They can even make the ground shake as it does during an earthquake.

Figure 6 When a jet plane reaches the speed of sound, the sound waves in front of the jet combine by constructive interference. The result is a high-density compression that is called the sound barrier.

You hear a sonic boom when the shock wave reaches you, not when the jet breaks the sound barrier.

On the edge of the cone, the sound waves combine by constructive interference to produce a shock wave.

Figure 7 When a jet travels at supersonic speeds, the sound waves it creates spread out behind it in a three-dimensional cone shape.

a

b

Constructiveinterference


vv--------------------------------------a

Interference in AuditoriumsDestructive interference can make it hard to hear in some parts of a theater or auditorium. To reduce the effects of destruc-tive interference, sounds are usually amplified electronically, and speakers are located in dif-ferent places. But sound waves from the many speakers can also produce destructive interference. Also, sound waves reflected from the walls and other surfaces can interfere with waves from the speakers. Have students find out how theaters, concert halls, and recording studios are designed and built to reduce destructive interference. Encourage them to use models or posters to show their results. l Visual

The speed of sound is about 343 m/s at sea level at 20°C and is known as Mach 1. As a plane passes through the sound barrier created at this speed, the resulting shock wave increases the drag on the plane. The plane has to be equipped to control this change in airflow.

Is That a Fact!A double sonic boom occurs when the space shuttle enters the atmosphere. Whenever a craft exceeds Mach 1, one shock wave is formed at the nose, and another shock wave is formed at the tail. If the shock waves are more than 0.10 s apart, you hear two sonic booms.

Interference and Standing WavesWhen you play a guitar, you can make some pleasing sounds, and you might even play a tune. But have you ever watched a guitar string after you’ve plucked it? You may have noticed that the string vibrates as a standing wave. A standing wave isa pattern of vibration that looks like a wave that is standing still. Waves and reflected waves of the same frequency are going through the string. Where you see maximum amplitude, waves are interfering constructively. Where the string seems to be standing still, waves are interfering destructively.

Although you can see only one standing wave, which is at the fundamental frequency, the guitar string actually creates several standing waves of different frequencies at the same time. The frequencies at which standing waves are made are called resonant frequencies. Resonant frequencies and the relationships between them are shown in Figure 8.

✓Reading Check What is a standing wave?

ResonanceIf you have a tuning fork, shown in Figure 9, that vibrates at one of the resonant frequencies of a guitar string, you can make the string make a sound without touching it. Strike the tuning fork, and hold it close to the string. The string will start to vibrate and produce a sound.

Using the vibrations of the tuning fork to make the string vibrate is an example of resonance. Resonance happens when an object vibrating at or near a resonant frequency of a second object causes the second object to vibrate.

standing wave a pattern of vibration that simulates a wave that is standing still

resonance a phenomenon that occurs when two objects naturally vibrate at the same frequency; the sound produced by one object causes the other object to vibrate

Figure 9 When struck, a tuning fork can make another object vibrate if they both have the same resonant frequency.

Higher resonant frequencies are called overtones. The first overtone is twice the frequency of the fundamental.

The second overtone is 3 times the fundamental.

The third overtone is 4 times the fundamental.

The lowest resonant frequency is called the fundamental.

Resonant Frequencies of a Plucked StringFigure 8


A standing wave is a pattern of vibration that looks like a wave that is standing still.

Reteaching -------------------------------------bBrainstorming Section ConceptsAsk students what the two main ideas in this section are. (reflection and interference of sound waves) If they mention resonance, ask them what more general concept it goes under. (interference) Then, have them name subtopics covered in this chapter and which of the two main ideas each is related to. (reflection: echoes, echolocation, ultrasonography; interference: con-structive interference, destructive interference, sound barrier, sonic boom, standing waves, resonance)l Logical

Quiz ---------------------------------------------------------------------g

1. Why does everything seem so quiet after a snowfall? (Snowdoes not reflect sound waves; it absorbs them.)

2. Have you ever sung in the shower? Why does your voice sound so much better there? (The hard, smooth walls of the shower reflect sound waves, and the interactions of the waves make your voice sound fuller.)


Sound Stories Have students write fictional articles for a tab-loid newspaper about a strange phenomenon caused by an interaction of sound waves they have learned about in this chap-ter. The science must be accu-rate, but they can exaggerate the effects. l Verbal

MISCONCEPTIONALERT

Fundamentals and Harmonics When overtones are exact multiples of the fundamental, they are often called har-monics. However, confusion sometimes results because harmonics are numbered to include the fundamental, but over-tones are not. As a result, the first over-tone is the second harmonic, the second overtone is the third harmonic, and so on.



SummarySummary

Review

Resonance in Musical InstrumentsMusical instruments use resonance to make sound. In wind instruments, vibrations are caused by blowing air into the mouthpiece. The vibrations make a sound, which is amplified when it forms a standing wave inside the instrument.

String instruments also resonate when they are played. An acoustic guitar, such as the one shown in Figure 10, has a hollow body. When the strings vibrate, sound waves enter the body of the guitar. Standing waves form inside the body of the guitar, and the sound is amplified.

Figure 10 Thebody of a guitar resonates when the guitar is strummed.

• Echoes are reflected sound waves.

• Some animals can use echolocation to find food or to navigate around objects.

• People use echoloca-tion technology in many underwater applications.

• Ultrasonography uses sound reflection for medical applications.

• Sound barriers and shock waves are created by interference.

• Standing waves form at an object’s resonant frequencies.

• Resonance happens when a vibrating object causes a second object to vibrate at one of its resonant frequencies.

Using Key Terms

1. Use the following terms in the same sentence: echo andecholocation.

Complete each of the following sentences by choosing the correct term from the word bank.

interference standing wavesonic boom resonance

2. When you pluck a string on a musical instrument, a(n) _____ forms.

3. When a vibrating object causes a nearby object to vibrate, _____ results.


4. What causes an echo?

a. reflectionb. resonancec. constructive interferenced. destructive interference

5. Describe a place in which you would expect to hear echoes.

6. How do bats use echoes to find insects to eat?

7. Give one example each of constructive and destructive interference of sound waves.

Math Skills

8. Sound travels through air at 343 m/s at 20°C. A bat emits an ultrasonic squeak and hears the echo 0.05 s later. How far away was the object that reflected it? (Hint: Remember that the sound must travel to the object and back to the bat.)

Critical Thinking

9. Applying Concepts Your friend is playing a song on a piano. Whenever your friend hits a certain key, the lamp on top of the piano rattles. Explain why the lamp rattles.

10. Making Comparisons Compare sonar and ultrasonography in locating objects.

Topic: Interactions of Sound WavesSciLinks code: HSM0804



1. Sample answer: Some ani-mals use echolocation to “see” in the dark by listening for the echoes of the sounds they make off reflected objects.

2. standing wave3. resonance4. a5. Sample answer: a room

with smooth walls6. They use echolocation to

find insects by emitting sounds and listening for the echoes, which tell them how far away the insect is and how fast it is moving.

7. Sample answer: construc-tive interference: sonic boom; destructive interference: a “dead spot” in a concert hall

8. 343 m/s � 0.05 s � 17 m 17 m � 2 � 8.5 m

9. Resonance is occurring, because the lamp on top of the piano has a resonant fre-quency equal to one of the notes being played.

10. Both sonar and ultrasonography make use of sound reflection to locate objects. Ultrasonography, however, involves much higher frequency sound waves than used in sonar and allows imag-ing of objects instead of just locating them.

CHAPTER RESOURCES


• Section Quiz g• Section Review g• Vocabulary and Section Summary g

CRF

Fundamental

First overtone

Second overtone

Resulting sound

READING STRATEGY

Sound QualityHave you ever been told that the music you really like is justa lot of noise? If you have, you know that people can disagreeabout the difference between noise and music.

You might think of noise as sounds you don’t like and musicas sounds that are pleasant to hear. But the difference betweenmusic and noise does not depend on whether you like thesound. The difference has to do with sound quality.

What Is Sound Quality?Imagine that the same note is played on a piano and on aviolin. Could you tell the instruments apart without looking?The notes played have the same frequency. But you could prob-ably tell them apart because the instruments make differentsounds. The notes sound different because a single note onan instrument actually comes from several different pitches:the fundamental and several overtones. The result of thecombination of these pitches is shown in Figure 1. The resultof several pitches mixing together through interference issound quality.sound quality. Each instrument has a unique sound quality.Figure 1 also shows how the sound quality differs when twoinstruments play the same note.

4

Figure 1 Each instrument has a unique sound quality thatresults from the particular blend of overtones that it has.

Violin

Piano

What You Will Learn

Explain why different instrumentshave different sound qualities.Describe how each family of musicalinstruments produces sound.Explain how noise is differentfrom music.

Vocabularysound qualitynoise

Reading Organizer As you readthis section, make a table comparingthe way different instrumentsproduce sound.

4

OverviewThis section defines sound qual-ity and explains how the threemain musical-instrument fami-lies (wind, percussion, andstring) produce sound. Studentslearn the difference betweenmusic and noise.

BellringerAsk the following questions:

• Which strings on a piano havelower pitch? (the longer andthicker strings)

• Why does a tuba have a lowerpitch than a trumpet? (Sampleanswer: A tuba has a longer andlarger air column.)

• Why are some sounds pleasingto hear and some sounds not?Explain your answer. (Accept allreasonable answers.)

Demonstration --------------g

Musical Instruments Ask twoor three different volunteerswho play musical instruments todemonstrate them for the class.Without discussing the differentfamilies of instruments, havestudents compare the soundquality of instruments within afamily and from different fami-lies. Tell the band or orchestramembers that they will have achance to perform later in thelesson. l Auditory

Is That a Fact!Many cultures write and play music ona basic eight-tone scale, although thenotes or tones may vary greatly fromscale to scale. Other cultures use a five-tone, or pentatonic, scale. Whicheverscale is used, each note has a character-istic frequency, and the notes span afrequency range called an octave.

CHAPTER RESOURCES



Technology

Transparencies • Bellringer

Workbooks



Sound Quality of InstrumentsThe difference in sound quality among different instrumentscomes from their structural differences. All instruments pro-duce sound by vibrating. But instruments vary in the part thatvibrates and in the way that the vibrations are made. There arethree main families of instruments: string instruments, windinstruments, and percussion instruments.

✓Reading Check How do musical instruments differ in how theyproduce sound? (See the Appendix for answers to Reading Checks.)

String InstrumentsViolins, guitars, and banjos are examples of string instruments.They make sound when their strings vibrate after being pluckedor bowed. Figure 2 shows how two different string instrumentsproduce sounds.

sound quality the result ofthe blending of several pitchesthrough interference

Cellos and guitars have strings of different thicknesses.The thicker the string is, the lower the pitch is.

The pitch of the string can be changed bypushing the string against the neck of theinstrument to change the string’s length.Shorter strings vibrate at higher frequencies.

A string vibrates when a bowis pulled across it or when

the string is plucked.

The vibrationsin the cello stringmake the bridgevibrate, which, in turn,makes the body of thecello vibrate.

An amplifier convertsthe electrical signalback into a soundwave and increasesthe loudness of thesound.

Pickups on the guitar convertthe vibration of the guitarstring into an electrical signal.

The body of the cello and the airinside it resonate with the string’svibration, creating a louder sound.

b

a

c

d

e

f

g

String InstrumentsFigure 2

READINGSTRATEGY -----------------g

Prediction Guide Before stu-dents read these two pages, askthem to name the three majorfamilies of musical instrumentsand to give as many examplesof each family as they can.l Logical


Musical instruments differ in the part of theinstrument that vibrates and in the way thatthe vibrations are made.

Is That a Fact!The pickup on an electric guitar is a setof magnets wrapped by thousands ofturns of wire. The vibrations of the gui-tar strings create disturbances in themagnetic fields. These disturbances pro-duce electrical impulses in the coils ofwire, and these impulses are transmittedto an amplifier, where they are con-verted into sounds.

SUPPORT FOR

English LanguageLearnersString Instruments Studentsmay have had little exposureto string instruments suchas violins. Ask the orchestradirector or students who playa string instrument to demon-strate how their instrumentswork. Before the demonstra-tion, have groups of studentswrite down questions to ask.Spot check the questionsorally for grammar. Ask thedemonstrator if students maystudy the instruments upclose after the demonstration.l Visual/Auditory

h-----------------------------g

The Sound of Music Havestudents write in their sciencejournal about a sound or somemusic that is important to them.The sound or music may havechanged their perspective aboutsomething, or maybe it changedtheir attitude or mood. Maybe itis just a favorite song. Ask themto explain why they think musiccan produce a change in a per-son’s mood. l Intrapersonal

Section 4 • Sound Quality 619

Wind InstrumentsA wind instrument produces sound when a vibration is created at one end of its air column. The vibration causes standing waves inside the air column. Pitch is changed by changing the length of the air column. Wind instruments are sometimes divided into two groups—woodwinds and brass. Examples of woodwinds are saxophones, oboes, and recorders. French horns, trombones, and tubas are brass instruments. A brass instrument and a woodwind instrument are shown in Figure 3.

Percussion InstrumentsDrums, bells, and cymbals are percussion instruments. They make sound when struck. Instruments of different sizes are used to get different pitches. Usually, the larger the instrument is, the lower the pitch is. The drums and cymbals in a trap set, shown in Figure 4, are percussion instruments.

The reed vibrates back and forth when a musician blows into a clarinet.

A trumpet player’s lips vibrate when the player blows into a trumpet.

Standing waves are formed in the air columns of the instruments. The pitch of the instrument depends in part on the length of the air column. The longer the column is, the lower the pitch is.

The length of the air column in a clarinet is changed by closing or opening the finger holes.

The length of the air column in a trumpet is changed by pushing the valves.

Cymbals vibrate when struck together or when struck with drumsticks.

The skins of the drums vibrate when struck with drumsticks.

Each drum in the set is a different size. The larger the drum is, the lower the pitch is.

d

c

e

ba

Wind InstrumentsFigure 3

Percussion InstrumentsFigure 4


Reteaching -------------------------------------bMusical Instruments and Sound Quality Have students name the three classes of musical instruments named in this sec-tion. Write each one on the board. Then, have them brain-storm as many examples of each one as they can think of. Write these in a second area on the board underneath each category. Then, have them explain what all instruments of each category have in common in how they produce sound and what deter-mines their particular sound quality. l Logical

Quiz ---------------------------------------------------------------------g

1. What is sound quality? (theresult of several pitches blending together through interference)

2. How does noise differ from music? (Music contains repeat-ing melodic patterns. Noise has a complex sound wave with no pattern.)


Instrument Diagrams Have students draw and label mem-bers of each instrument family. Instruct them to label the part that vibrates and show where or how pitch can be changed. l Verbal ee

CulturalAwarenessCulturalAwareness g

Use of Drums Drums, the most com-mon percussion instruments, have been around since at least 6000 BCE. Drums are found in almost every culture and have been used for a number of purposes, including music. In some African cultures, drums were used to transmit messages over many miles. In Europe, infantry regiments once used snare drums to transmit coded orders to soldiers.

For a variety of links related to thischapter, go to www.scilinks.org


SummarySummary

Review

Music or Noise?Most of the sounds we hear are noises. The sound of a truckroaring down the highway, the slam of a door, and the jingleof keys falling to the floor are all noises. Noise can be describedas any sound, especially a nonmusical sound, that is a randommix of frequencies (or pitches). Figure 5 shows on an oscillo-scope the difference between a musical sound and noise.

✓Reading Check What is the difference between musicand noise?

noise a sound that consists ofa random mix of frequencies

Figure 5 A note from a Frenchhorn produces a sound wave witha repeating pattern, but noise froma clap produces complex soundwaves with no regular pattern.

French horn A sharp clap

• Different instrumentshave different soundqualities.

• Sound quality resultsfrom the blendingthrough interferenceof the fundamentaland several overtones.

• The three familiesof instruments arestring, wind, and percus-sion instruments.

• Noise is a soundconsisting of a randommix of frequencies.

Using Key Terms

1. Use each of the following termsin a separate sentence: soundquality and noise.


2. What interaction of soundwaves determines sound quality?

a. reflection c. pitchb. diffraction d. interference

3. Why do different instrumentshave different sound qualities?

Critical Thinking

4. Making Comparisons Whatdo string instruments and windinstruments have in common inhow they produce sound?

5. Identifying Bias Someone saysthat the music you are listen-ing to is “just noise.” Does theperson mean that the music isa random mix of frequencies?Explain your answer.

Interpreting Graphics

6. Look at the oscilloscope screenbelow. Do you think the soundrepresented by the wave on thescreen is noise or music? Explainyour answer.

Topic: Sound QualitySciLinks code: HSM1427


1. Sample answer: Each instrumenthas a different sound qualitybased on how it produces sound.Static from the TV or radio is anexample of noise.

2. d3. A musical instrument’s particular

shape and way of producingsound give it its unique soundquality.

4. String instruments and windinstruments both make standingwaves, string instruments alongthe string and wind instrumentsinside the air column, to producesound.

5. probably not; People use theword noise in common speech tomean any unpleasant sound,which might be applied by some-one to a particular kind of musiceven if that music is not merely arandom mix of frequencies.

6. The sound is music. The oscillo-scope shows an image of a wavewith a repeating pattern.


Music consists of sound waves that have regu-lar patterns, and noise consists of a random mixof frequencies.

CHAPTER RESOURCES


• Section Quizg• Section Reviewg• Vocabulary and Section Summaryg• Critical Thinkinga

Technology

Interactive Explorations CD-ROM• Sound Bite!g

CRF

Section 4 • Sound Quality 621

Measure your classmates’ability to detect differentpitches at different distances.

Graph the average class data.

Form a conclusion abouthow easily pitches of differentfrequencies are heard atdifferent distances.

• eraser, hard rubber

• meterstick

• paper, graph

• tuning forks, differentfrequencies (4)

Easy ListeningPitch describes how low or high a sound is. A sound’s pitchis related to its frequency—the number of waves per second.Frequency is measured in hertz (Hz), where 1 Hz equals 1wave per second. Most humans can hear frequencies in therange from 20 Hz to 20,000 Hz. But not everyone detects allpitches equally well at all distances. In this activity, you willcollect data to see how well you and your classmates heardifferent frequencies at different distances.

Ask a Question

1 Do most of the students in your classroom hear low-, mid-, orhigh-frequency sounds best?

Form a Hypothesis

2 Write a hypothesis that answers the question above. Explainyour reasoning.

Test the Hypothesis

3 Choose one member of your group to be the sound maker.The others will be the listeners.

4 Copy the data table below onto another sheet of paper. Besure to include a column for every listener in your group.

5 The sound maker will choose one of the tuning forks, andrecord the frequency of the tuning fork in the data table.

6 The listeners should stand 1 m from the sound maker withtheir backs turned.

OBJECTIVES

MATERIALS

Data Collection Table

Frequency

Distance (m)

Listener 1 Listener 2 Listener 3 Average

1 ( _____Hz)

2 ( _____Hz)

3 ( _____Hz)

4 ( _____Hz)

DO NOT WRITE IN BOOKDO NOT WRITE IN BOO

LabSkills PracticeUsing Scientifi c MethodsSkills PracticeSkills Practice LabLab

Easy Listening

Teacher’s Notes

Time RequiredOne or two 45-minute classperiods

Lab Ratings

rTeacher Prep f

Student Set-Up f

Concept Level ff

Clean Up f

M A T E R I A L SFOR EACH GROUP OF 3 TO 4STUDENTS

• eraser, hard rubber (or tuningfork mallet)

• meterstick• paper, graph• tuning forks, different

frequencies (4)

Form a Hypothesis

2. Sample answer: Most of the students in the class will hearmid-frequency sounds better.(Accept any testable hypothesis.)

Lab NotesYou may wish to use the classroom graphto have students practice interpreting agraph. For instance, you could ask studentsto try and pinpoint the distances at whichother frequencies might be heard based onthe graph.

CHAPTER RESOURCES


CRF • Datasheet for Chapter Lab• Lab Notes and Answers

Technology

Classroom Videos• Lab Video

• The Speed of Sound• Tuneful Tube• The Energy of Sound


7 The sound maker will create a sound bystriking the tip of the tuning fork gently withthe eraser.

8 Listeners who hear the sound should take onestep away from the sound maker. The listenerswho do not hear the sound should stay wherethey are.

9 Repeat steps 7 and 8 until none of thelisteners can hear the sound or the listenersreach the edge of the room.

0 Using the meterstick, the sound maker shouldmeasure the distance from his or her positionto each of the listeners. All group membersshould record this data.

q Repeat steps 5 through 10 with a tuning forkof a different frequency.

w Continue until all four tuning forks have beentested.

Analyze the Results

1 Organizing Data Calculate the average dis-tance for each frequency. Share your group’sdata with the rest of the class to make a datatable for the whole class.

2 Analyzing Data Calculate the average dis-tance for each frequency for the class.

3 Constructing Graphs Make a graph of theclass results, plotting average distance (y-axis)versus frequency (x-axis).

Draw Conclusions

4 Drawing Conclusions Was everyone in theclass able to hear all of frequencies equally?(Hint: Was the average distance for eachfrequency the same?)

5 Evaluating Data If the answer to question 4is no, which frequency had the longest averagedistance? Which frequency had the shortestfinal distance?

6 Analyzing Graphs Based on your graph, doyour results support your hypothesis? Explainyour answer.

7 Evaluating Methods Do you think your classsample is large enough to confirm yourhypothesis for all people of all ages? Explainyour answer.

Analyze the Results

1. You may wish to provide a tableon the board or on an overheadtransparency for students torecord their data. The tableshould include a column foreach group and a row for thedistance measurement foreach tuning fork.

2. Calculate the class averagefor each frequency. All studentsshould have the same averages.

3. The graph will vary dependingon what frequencies are used,surrounding noise levels, andindividual hearing abilities.See the sample graph below:

Draw Conclusions

4. The average distance for eachfrequency should be different.

5. Answers will depend on whichfrequencies were used. Acceptall answers that agree withclass data.

6. Answers will vary depending onhypotheses. Accept all reason-able responses.

7. The class sample is not enoughto confirm the hypothesis forall humans of all ages, becausemost people in the classroomare the same age. In addition,the number of students in anaverage classroom is just toosmall to provide results thatcan be extended to the general population.

CHAPTER RESOURCESWorkbooks

Whiz-Bang Demonstrations• Hear Ye, Hear Yeg• Jingle Bells, Silent Bellsg• The Sounds of Timeg• A Hot Toneg

EcoLabs & Field Activities• An Earful of Soundsb

Long-Term Projects & Research Ideas• The Caped Ace Flies Againa

Aver

age

dist

ance

Frequency

Terry Rakes

Elmwood Junior HighRogers, Arkansas

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Chapter 21 • Chapter Lab 623

Complete each of the following sentences by choosing the correct term from the word bank.

loudness echoespitch noisesound quality

1 The _____ of a sound wave depends on its amplitude.

2 Refl ected sound waves are called _____.

3 Two different instruments playing the same note sound different because of _____.

Multiple Choice

4 If a fi re engine is traveling toward you, the Doppler effect will cause the siren to sound

a. higher. c. louder.b. lower. d. softer.

5 Sound travels fastest through

a. a vacuum. c. air.b. sea water. d. glass.

6 If two sound waves interfere construc-tively, you will hear

a. a high-pitched sound.b. a softer sound.c. a louder sound.d. no change in

sound.

7 You will hear a sonic boom when

a. an object breaks the sound barrier.b. an object travels at supersonic

speeds.c. a shock wave reaches your ears.d. the speed of sound is 290 m/s.

8 Resonance can happen when an object vibrates at another object’s

a. resonant frequency.b. fundamental frequency.c. second overtone frequency.d. All of the above

9 A technological device that can be used to see sound waves is a(n)

a. sonar. c. ultrasound.b. oscilloscope. d. amplifi er.

Short Answer

0 Describe how the Doppler effect helps a beluga whale determine whether a fi sh is moving away from it or toward it.

q How do vibrations cause sound waves?

w Briefl y describe what happens in the different parts of the ear.

Math Skills

e A submarine that is not moving sends out a sonar sound wave traveling 1,500 m/s, which refl ects off a boat back to the submarine. The sonar crew detects the refl ected wave 6 s after it was sent out. How far away is the boat from the submarine?

USING KEY TERMS

UNDERSTANDING KEY IDEAS

12. In the outer ear, sound waves are funneled into the ear canal. In the middle ear, the hammer, anvil, and stirrup increase the size of the vibrations. In the inner ear, these vibrations are changed into electrical sig-nals for the brain to interpret.

13. 1,500 m/s � 6 s � 9,000 m 9,000 m � 2 � 4,500 m

ANSWERS

Using Key Terms1. loudness2. echoes3. sound quality

Understanding Key Ideas4. a5. d6. c7. c8. d9. b

10. If a fish is moving away from the whale, the echo off the fish that the whale hears will have a lower pitch than the original sound. If the fish is moving toward the whale, the echo off the fish heard by the whale will have a higher pitch than the original sound.

11. The back-and-forth motions of vibrations of an object cause compressions and rarefactions in the air around it, which is carried outward as sound waves.

Assignment GuideSECTION QUESTIONS

1 11–12, 17

2 1, 4–5, 9–10, 13, 19–20

3 2, 6–8, 15–16

4 3, 18, 21

2 and 3 14


rConcept Mapping Use the followingterms to create a concept map:sound waves, pitch, loudness, decibels,frequency, amplitude, oscilloscope,hertz, and interference.

tAnalyzing Processes An anechoicchamber is a room where there isalmost no refl ection of sound waves.Anechoic chambers are often used totest sound equipment, such as stereos.The walls of such chambers are usuallycovered with foam triangles. Explainwhy this design eliminates echoes inthe room.

yApplying Concepts Would the pilot ofan airplane breaking the sound barrierhear a sonic boom? Explain why orwhy not.

uForming Hypotheses After workingin a factory for a month, a man youknow complains about a ringing in hisears. What might be wrong with him?What do you think may have causedhis problem? What can you suggest tohim to prevent further hearing loss?

Use the oscilloscope screens below toanswer the questions that follow:

i Which sound is noise?

o Which represents the softest sound?

p Which represents the sound with thelowest pitch?

aWhich two sounds were produced bythe same instrument?

CRITICAL THINKING INTERPRETING GRAPHICS

a b

c d

Critical Thinking14. An answer to this

exercise can befound at the endof this book.

15. This design eliminates echoesbecause the surfaces of thewalls absorb most soundwaves instead of reflectingthem.

16. no; A sonic boom is only audi-ble to an observer behind theplane along the shock wave.Once the airplane breaks thesound barrier, the plane out-runs the sonic boom, so thepilot does not hear it.

17. The worker may be sufferingfrom tinnitus, caused by longexposure to loud sounds.Further hearing loss could beprevented by wearing hearingprotection while on the job.

Interpreting Graphics18. d19. a20. c21. b, c

CHAPTER RESOURCES


CRF • Chapter Reviewg• Chapter Test Ag• Chapter Test Ba• Chapter Test Cs• Vocabulary Activityg

Workbooks

Study Guide• Study Guide is also available in Spanish.

Chapter 21 • Chapter Review 625

READING

MISCONCEPTIONALERT

Answers to the standardized test preparation can help you identify student misconcep-tions and misunderstandings.

Teacher’s NoteTeacher’s NoteTo provide practice under more realistic testing conditions, give students 20 minutes to answer all of the questions in this Standardized Test Preparation.

READINGRead each of the passages below. Then, answer the questions that follow each passage.

Passage 1 Centuries ago, Marco Polo wrote about the booming sand dunes of the Asian desert. He wrote that the booming sands filled the air with the sounds of music, drums, and weapons of war. Booming sands are most often found in the middle of large deserts. They have been discovered all over the world, including the United States. Booming sands make loud, low-pitched sounds when the top layers of sand slip over the layers below, producing vibrations. The sounds have been compared to foghorns, cannon fire, and moaning. The sounds can last from a few seconds to 15 min and can be heard more than 10 km away!

1. Which is a fact in this passage?

A Marco Polo loved traveling.B Booming sands always sound like moaning

people.C Booming sands are the most interesting

thing in Asia.D Some booming sands are found in the

United States.

2. Which of the following phrases best describesbooming sands?

F found in AsiaG noisyH slipperyI discovered by Marco Polo

3. What causes booming sands?

A vibrations caused by top layers of sand slipping over layers below

B battles in the desertC animals that live beneath sand dunesD There is not enough information to

determine the answer.

Passage 2 People who work in the field of architectural acoustics are concerned with controlling sound that travels in a closed space. Their goal is to make rooms and buildings quiet yet suitable for people to enjoy talking and listening to music. One major factor that affects the acoustical quality of a room is the way the room reflects sound waves. Sound waves bounce off surfaces such as doors, ceilings, and walls. Using materials that absorb sound reduces the reflection of sound waves. Materials that have small pockets of air that can trap the sound vibrations and keep them from reflecting are the most sound absorbent. Sound-absorbing floor and ceiling tiles, curtains, and upholstered furniture all help to control the reflection of sound waves.

1. The fi eld of architectural acoustics is concerned with which of the following?

A making buildings earthquake safeB controlling sound in closed spacesC designing sound-absorbing materialsD making buildings as quiet as possible

2. Which of the following is a major factor in the acoustical quality of a room?

F the size of the roomG the furnishings in the roomH the walls of the roomI the noise level in the room

3. Which of the following materials is most likely to absorb sounds the best?

A materials that have small pockets of airB surfaces such as doors, ceilings, and wallsC materials that keep the room as quiet as

possibleD furniture that is made of wood

Passage 11. D2. G3. A

Question 2: The key to this ques-tion is zeroing in on the one most defining aspect of booming sands among the descriptors shown. Although they are found in Asia, this is not a defining aspect of booming sands: they are found elsewhere. Booming sands can be caused by slip-page of sand over sand dunes, but “slippery” is not the best way to describe them. Booming sands were described by Marco Polo, but this is, again, not a defining aspect of boom-ing sands. The best answer choice is G, “noisy,” because this is the one quality referred to most throughout the passage.

Passage 21. B2. H3. A

Question 3: Students may be tempted to select answer C, but it is not an actual description of the types of materials that are likely to absorb sound. Furniture is mentioned in the passage as a minor factor in room acoustics, but the passage names materials that have small pockets of air as the best sound-absorbing material. Answer A is therefore correct.


Chapter 21 • Standardized Test Preparation 627

CHAPTER RESOURCES


CRF • Standardized Test Preparation g

State Resources

For specifi c resources for your state, visit go.hrw.com and type in the keyword HSMSTR.

Sta

nd

ardize

d Te

st Pre

pa

ratio

n

Use the pictures of standing waves below to answer the questions that follow.

Read each question below, and choose the best answer.

1. Which of the standing waves has the lowest frequency?

A aB bC cD d

2. Which of the standing waves has the highest frequency?

F aG bH cI d

3. Which of the standing waves represents the fi rst overtone?

A aB bC cD d

4. In which of the following pairs of standing waves is the frequency of the second wave twice the frequency of the fi rst?

F a, bG a, cH b, cI c, d

1. The speed of sound in copper is 3,560 m/s. Which is another way to express this measure?

A 356 � 102 m/sB 0.356 � 103 m/sC 3.56 � 103 m/sD 3.56 � 104 m/s

2. The speed of sound in sea water is 1,522 m/s. How far can a sound wave travel underwater in 10 s?

F 152.2 mG 1,522 mH 15,220 mI 152,220 m

3. Claire likes to go swimming after work. She warms up for 120 s before she begins swimming, and it takes her an average of 55 s to swim one lap. Which equation could be used to fi nd w, the number of seconds it takes for Claire to warm up and swim 15 laps?

A w � (15 � 120) � 55B w � (15 � 55) � 120C w � 120 � 55 � 15D w � (15 � 55) � 120

4. The Vasquez family went bowling. They rented 6 pairs of shoes for $3 a pair and bowled for 2 h at a rate of $8.80/h. Which is the best estimate of the total cost of the shoes and bowling?

F $24G $30H $36I $45

INTERPRETING GRAPHICS MATH

(a)

(b)

(c)

(d)

INTERPRETING GRAPHICS1. A2. I3. B4. F

Question 3: The first overtone should not be confused with the first harmonic, which is the same as the fundamental. The first overtone is the standing wave with twice the fre-quency (and half the wavelength) of the fundamental.

MATH1. C2. H3. B4. H

Question 3: If students recognize that the order of operations for addi-tion is not important, they will recog-nize B as the correct answer. If they do not, they may think that the fact that the 120 s of warmup is mentioned first in the passage means they should look for the 120 s to come first in the equation, and they may be tempted to choose C.

Sciencein Action

in Action

Language ArtsRead “Ear,” by Jane Yolen, in the Holt Anthology of Science Fiction.

Write a one-page report that discusses how the story made you think about the impor-tance of hearing in your everyday life.

MathImagine that a standing wave with a frequency of 80 Hz is made inside the crest of a Parasaurolophus. What would be the frequency of the first overtone of this standing wave? the second? the third?

WRITINGSKILL

Scientific DiscoveriesJurassic BarkImagine you suddenly hear a loud honking sound, such as a trombone or a tuba. “Must be band tryouts,” you think. You turn to find the noise and find yourself face to face with a 10 m long, 2,800 kg dinosaur with a huge tubular crest on its snout. Do you run? No—your musical friend, Parasaurolophus, is a vegetarian. In 1995, an almost-complete fossil skull of an adult Parasaurolophus was found in New Mexico. Scientists studied the noise-making qualities of Parasaurolophus’s crest and found that it contained many internal tubes and chambers.

Science Fiction“Ear” by Jane YolenJily and her friends, Sanya and Feeny, live in a time not too far in the future. It is a time when everyone’s hearing is damaged. People communicate using sign language—unless they put on their Ear. Then, the whole world is filled with sounds.

Jily and her friends visit a club called The Low Down. It is too quiet for Jily’s tastes, and she wants to leave. But Sanya is dancing by herself, even though there is no music. When Jily finds Feeny, they notice some Earless kids their own age. Earless people never go to clubs, and Jily finds their presence offensive. But Feeny is intrigued.

Everyone is given an Ear at the age of 12 but has to give it up at the age of 30. Why would these kids want to go out without their Ears before the age of 30? Jily thinks the idea is ridiculous and doesn’t stick around to find out the answer to such a question. But it is an answer that will change her life by the end of the next day.


Science, Technology,

and Society

BackgroundComputed axial tomography (CAT scanning), which has been used for many years in medicine, is now being used by paleontolo-gists to study the internal struc-ture of fossils. CAT scanning can provide interior views of a fos silwithout touching the fossil’s surface. If a paleontologist needs to reconstruct an entire skull, a series of two-dimensional “slice” shots are taken and combined through computer imaging to produce a three-dimensional image of the skull—inside and out!

Science Fiction

BackgroundAs a Caldecott Award winner, National Book nominee, and Nebula finalist, Jane Yolen knows how to write successful stories. Her work spans a wide range of topics—from imagina-tive alphabet books for the youngest reader to serious novels for the young-adult and adult audience. The inspiration for much of Yolen’s work comes from folktales and stories with rich histories.

Answer to Math Activity

The first overtone would be twice the frequency of the fundamental, so the frequency would be 80 Hz � 2 � 160 Hz. The second overtone would be 80 Hz � 3 � 240 Hz. The third overtone would be 80 Hz � 4 � 320 Hz.

Answer to Language Arts Activity

Answers may vary.

Check out Current Science®

articles related to this chapterby visiting go.hrw.com. Justtype in the keyword HP5CS21.

Careers

Social StudiesSocial Studies

Research the ways in whichconcert halls were designedbefore the use of electricamplification. Make a model ordiorama, and present it to theclass, explaining the acousticalfactors involved in the design.

Adam DudleySound Engineer Adam Dudley uses the science of sound waves every day at his job.He is the audio supervisor for the Performing Arts Center of the University of Texas atAustin. Dudley oversees sound design and technical support for campus performancespaces, including an auditorium that seats over 3,000 people.

To stage a successful concert, Dudley takes many factors into account. The sizeand shape of the room help determine how many speakers to use and where to placethem. It is a challenge to make sure people seated in the back row can hear wellenough and also to make sure that the people up front aren’t going deaf from thehigh volume.

Adam Dudley loves his job—heenjoys working with people andtechnology and prefers not to weara coat and tie. Although he is invis-ible to the audience, his work back-stage is as crucial as the musiciansand actors on stage to the successof the events.

To learn more about theseScience in Action topics, visitgo.hrw.com and type in thekeyword HP5SNDF.

Careers

BackgroundThe physics of sound is veryimportant in the field of soundengineering. For instance,speakers placed in differentlocations in a concert hall mustbe placed in such a way thatdestructive interference does notcreate dead spots. Also, some-times extra speakers are placedin the balcony to reinforce thesound coming from the speakersnear the stage. But because ofthe difference in speed betweenthe signal coming through thewire and the sound travelingthrough air, people in the bal-cony may hear a delay betweenthe sound coming from the bal-cony speakers and that comingfrom speakers near the stage.This problem requires a correc-tion in the signal to the balconyspeakers, delaying it by a frac-tion of a second to compensate.

Answer to Social Studies Activity

Answers may vary.

Chapter 21 • Science in Action 629

21 the nature of sound compression guide: chapter …21 the nature of sound chapter planning guide...

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