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Nancy Larson PublishersScienco 2, Booklet E

ExploringSound ond

Light

Physics

Physicist

Whot Couses Sound

!r' t Wehear sounds of home, of school, ond on the ployground. Some of these

sounds are made by people ond onimols. Other sounds ore mode by mochines.

Moving oir ond water con olso moke sounds.

2 Sound occurs when something vibrotes. When on object vibnotes, sound

woves move outword in oll directions from the vibroting object. Sound woves

cqnnot be seen.

3 Sound woves con poss through solids, liquids, ond goses. Physicists know

thot sound woves trovel fostest through solids ond slowest through gosas.

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Loud ond Soft Sounds

t 4 loud sound is cous ed by very large vibrotions. When Ihere are ve?y smoll

vibrotions, o sound will be soft ond moy be difficult to heor.

2 Sounds moy seem louder or softer, depending on how close we ereto the

source of the sound. Tf we are next to o vibroting object, the sound we heor is

louder thon when we a?e forther owoy.

Loud Sounds Soft Sounds

vibrotions Cr tl vibrationsJ

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Meosuring the Loudness of Sounds

1 The loudness of o sound is meosured in decibels. The softest possible

sound hos o decibel levelof 0. Most peoplecon heor sounds obove 10 decibels.

Sounds obove 90 decibels con domoge our heoring. Sounds obove l?O decibels

ore poinful to our eors.

Humon-mode noise thot is hormful to people is colled noise pollution. Loud

music, loud vehicles, ond loud construction equipment all createnoise pollution.

Noise pollution con domogeourhearing. ft con olso moke it difficult for us to

sleep or to concentrate when we work. ,.,

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Decibel Scole

Loudness SoundDecibel Level

(dB)

Very louda,

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120

Loud .- t.\o/', t i lV. ,' :': / l,'100

4 rr,{Y, 80

Average 60

Wlr'';;' i 30

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Science 2 @ Nancy Larson. All rights reserved. 5

Sound Woves

t When sound woves hit on object, some of the sound woves poss through

the object. Other sound woves ore obsorbed by the object or are reflected by

the object.

2 Soft objects ond objects with uneven surfoces absorb, or sook up, sound

woves. Curtoins, rugs, pillows, clothing, and plonts are objects thot obsorb

sound woves. fnsulotion in the wolls ond ceiling of a room olso obsorbs sound

woves. Rooms with mony soft objects ore quieter thon rooms without them.

3 Hord, smooth surfaces reflect, or send bock, sound woves. Metol, wood,

ond concreFe objects reflecl sound woves. Rooms with mony hord, smooth

surfoces oftenseem loud ond noisy becouse of reflected sound woves. The

reflected sound is colled an echo.

o Focusing sound woves in one direction con moke the sound woves trovel

farther.Tf we speok into empty tubes, megophones, or our cupped honds held

nesr our mouths, we focus the sound woves in one direction. The sound of our

voices trovels f arther ond seems louder.

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How Humon Beings Hear Sounds

1 our ears a?e the sense orgons thot ollow us to heor sounds. The humo n ear

hos three sections: the external ear,the middle ear,ond the inner eor.

2 The externol eor includes the port of the ear we see.The outer port of

theeor, colled the pinno, cotches sound woves tikeo cupped hond. From the

pinno, the sound woves move through the ear cqnol to the eordrum. The sound

woves moke the eardrum vibrote.Theeordrum separates the external ear from

the middle ear.

3r" ln the middle ear there are three tiny bones colled the moleus, incus, ond

stopes. The vibrotions from lhe eardrum trovel throuqh these threebones tobthe ovol window. The ovol window seporotes the middle ear f rom the inner ear.

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s47; r'n the inner ear, the vibrotions trovel through fluid in the cochleo. fnHz! the cochleo, the vibrotions ore tronsfer red to the oudit ory nerve. The ouditory5.2tr- sends o messogeto the broin ond our broins tell us whot weheor.E ne?ve:Eo':>!o

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Externol Eqr

1. p*hno" ?. eor conol

The Humqn Eor

Middle Eor

+. .mgUeus (hommer)

5. *qg. (onvil)

fnner Eor

8. cochlea

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6. stooes

\ (stirrup)

7. ovol window.%!k'*"

8 O Nancy Larson. All rights reserved Science 2

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L/Pitch of o Sound

1 Pitch is how high or low o sound is. Musicol instruments produce sounds

with diff erent pitches.

2 A xylophone hos bors of diff erent lengths thot aretapped with o mollet.

When a bor is topped, it vibnotes. Eoch bor produces o sound with o diff erenl

pitch. Shorter bors moke higher-pitched sounds thon longer bors.

3 stringed instruments, such os guitors ond violins, hovestrings thot vibrote

to produce sounds. Eoch string produces o sound with o different pitch. A piono

olso hos strings. The strin gs are of diff erent lengtrhs. Short er strings on o

piono produce sounds with high er pilches thon longer strings.

4 ShorFening o string on on instrumenf con produce ahigher-pitched sound.

You con shorten the port of o string thot vibrotes on o guito r by pressing your

f inger on the string. The shorter strin g will produce o sound with o higher

pitch.

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Pitch olso depends on the thickness of o string. A thin string on o guitor

a higher pitch thcn o thick string of thesome length.

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6 The tightness of o string also aff ects the pitch . Wheno string on o guitor

is stretch ed tighter, the pitch becomes higher.

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Pitch Experiment I

Purpose: To observe how chonging the tightness of o rubber bond aff ecls pitch.

Moteriols: Rubber bond, cordboord or plostic box

Procedure: 1. Put o rubber bond oround on open box.

2. Pluck the bond ond listen to the pitch.

3. Use one hond to pull the bond tighler ot the side of the box.

4. U;E your other hond to pluck the bond. Listen to the pitch.

5. Compore the pitches.

Collect How did the pitch chonge when the bond wos pullad tighter?l,fur {uhh{r- L*,*# rr.i,4{

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Conclusion: Whot did you leorn from this experiment?'.1

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Pitch Experiment 2

Purpose: To observe how chonging thelenglh of o rubber bond offects pitch.

Moterials: Rubber bond, cordboord or plostic box

Procedure: 1. Put o rubber bond oround on open box.2. Pluck the bond ond listen to the pitch.3. Shortenrhelength of the vibroting bond by using two fingers

on one hond to pinch the bond over 'fhe opening ol the boi.4- Use your other hond to pluck the bond. Listen to the pitch.5. Compore the pitches.

Collect Doto: How did the pitch change when the bond wos shorlened?lr

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Conclusion: Whot did you learn from Ihis experiment?:T Iii

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Pitch ActivityProcedure: 7. Place three diff erent-sized rubber bonds oround on

2. Put the bonds in order from lowest pitch to highest3. Ask someone to check tha pitch of your bonds.4. Moke up o song using your rubber-bond instrument.

open box.

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Science 2 O Nancy Larson. Al1 rights reservecl 11

Light

r The Sun, f ire, lightning, ond light bulbs ore oll sources of light. Light

spneods out in oll directions from the source of the light. Light trovels in

stroight lines colled roys.

' Light trovels fosler thon sound. This is why we seeFhe light from lightning

beforewehear the sound of thunder, even though they both occur of the some

time.

3 Light con poss through fronsporent motter, such os gloss ond oir. Only

some light posses through tronslucent motter, such os woter ond thin poper.

4 Light connot poss through opoque motter. Motter thot is opoque reflects

light, obsorbs light, on does both. We see shodows behind opoque objects

because the light is reflected or obsonbed.

Tronsporent Tronslucent Opoque

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The Colors of Light

1 The light from the Sun is colled white light. This light seems to be

colorless. More thon 300 yeors ogo, o scientist nomed Sir fsaoc Newton

discovered thot white light is mode of sevendifferent colors. The colors thot

moke up white light are red, orange,yellow, green, blue, indigo, ond violet.

2 The seven colors thot moke up white light ore called the light spectrum.

The lighf spectrum con be seen in o roinbow or when light posses through o

prism. All the other colors we see are made from combinotions of the seven

colors in the light spectrum.

The Colors of the Light Spectrum

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Red Orange

ROy

Yellow Green

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Blue fndigo

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Violet

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The Colors We See

' WheH light roys hit on object , Fhecolor we seedepends on which colors b'

in the light spectrum are reflected. A red opple oppeors red because the

opple reflects the red light ond obsorbs most of the other colors of the light

spectrum. A leaf oppeors green becouse the leaf reflects the green light ond

obsorbs most of the other colors of the light spectrum.

z Tf on object reflects oll of the colors in tha light spectrum ,the object

oppeors white. This poper oppeors white to us becouse it reflects oll the colons

in the light spectrum, ond no colors ore absorbed.

: ff on object obsorbs olmost all of tha colors in the light spectrum , the

object oppeors block. The words on this page oppeor block becouse most colors

in the light spectrum ore obsorbed, ond olmost none are reflected.a6''o0a@5

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