Sound WavesSound WavesChapter 16Chapter 16

Old RiddleOld Riddle

If a tree falls in the If a tree falls in the middle of a forest and middle of a forest and no one is around, does it no one is around, does it make a sound?make a sound?

AnswerAnswer

To a scientist, the tree does make a To a scientist, the tree does make a sound no matter whether someone sound no matter whether someone hears it or not.hears it or not.

Sound- disturbance that travels Sound- disturbance that travels through a medium as a longitudinal through a medium as a longitudinal wavewave

Sound WaveSound Wave

Sound WavesSound Waves Sound Waves reflect, Sound Waves reflect,

diffract through narrow diffract through narrow openings and around openings and around barriers, and interfere barriers, and interfere with each otherwith each other

Reflection- sounds Reflection- sounds bounce off surfaces bounce off surfaces such as wallssuch as walls A reflected sound wave A reflected sound wave

is called an echois called an echo

DefractionDefraction Why can you hear Why can you hear

someone in a someone in a classroom before you classroom before you enter the room?enter the room? Sound waves do not Sound waves do not

travel in straight linetravel in straight line They expand and They expand and

contract to fill the room contract to fill the room which they are enteringwhich they are entering

InterferenceInterference

Interference- when waves interact Interference- when waves interact with each otherwith each other Constructive Constructive DestructiveDestructive

Speed of SoundSpeed of Sound If a sound wave is traveling through If a sound wave is traveling through

air at room temperature, the speed air at room temperature, the speed of the wave is 343 m/s.of the wave is 343 m/s.

The speed of sound depends on The speed of sound depends on many factors such as elasticity, many factors such as elasticity, density, and temperature of the density, and temperature of the medium through which it is medium through which it is traveling.traveling.

Turn to pg 543. Look at the Math Turn to pg 543. Look at the Math Analyzing Data and do problems 1-3Analyzing Data and do problems 1-3..

Elasticity- ability of a material to Elasticity- ability of a material to bounce back after being bounce back after being disturbeddisturbed Which is more elastic?Which is more elastic?

Modeling clayModeling clay Rubber bandRubber band

The more elastic a medium, the The more elastic a medium, the faster the sound travels.faster the sound travels. Solid- more elasticSolid- more elastic Liquid- middle elasticLiquid- middle elastic Gas- Least elasticGas- Least elastic

ElasticityElasticity

Density- how much matter that Density- how much matter that is in an objectis in an object In an object with the same state In an object with the same state

(solid, liquid, gas), sound travels (solid, liquid, gas), sound travels slower in denser object.slower in denser object.

Why?Why?The particles do not move as The particles do not move as quickly in denser objectquickly in denser object

DensityDensity

Temperature- how Temperature- how quickly particles movequickly particles move Sound travels more Sound travels more

slowly in lower slowly in lower temperaturestemperatures

Which wins? Put in order Which wins? Put in order from fastest to slowest.from fastest to slowest. 30º C30º C 20º C20º C 10º C10º C 0º C0º C

TemperatureTemperature

Loudness- perception of energy Loudness- perception of energy of a soundof a sound

Loudness depends on two things: Loudness depends on two things: the amount of energy it takes to the amount of energy it takes to make the sound and the distance make the sound and the distance from the source of the soundfrom the source of the sound Shouting vs. whisperingShouting vs. whispering The closer to a sound you are, the The closer to a sound you are, the

louderlouder

LoudnessLoudness

The greater the energy The greater the energy used to make the sound, used to make the sound, the louder the sound.the louder the sound.Guitar String- more energy Guitar String- more energy used to pick the string up, used to pick the string up, the louder it is.the louder it is.The more energy that is The more energy that is used, the higher the used, the higher the amplitude.amplitude.

Loudness increases as you get Loudness increases as you get closer to the origination of the closer to the origination of the sound.sound. Why?Why?

The closer you are to the origination The closer you are to the origination of the sound, the smaller the wave of the sound, the smaller the wave and the more energy you hear.and the more energy you hear.

As a sound wave travels, the waves As a sound wave travels, the waves spread and energy is also spread spread and energy is also spread out.out.

IntensityIntensity

Intensity- the amount of energy Intensity- the amount of energy a sound waves carries per a sound waves carries per second through a unit areasecond through a unit area

A sound wave with a greater A sound wave with a greater intensity, sounds louder.intensity, sounds louder.

As you walk away, it gets softer As you walk away, it gets softer and intensity goes down.and intensity goes down.

Loudness is measured Loudness is measured in decibels (dB)in decibels (dB)Loudness of what we Loudness of what we can barely hear is 0dBcan barely hear is 0dB

30 dB is 3 times the 30 dB is 3 times the level of 10 dBlevel of 10 dB

Sounds louder than 100 Sounds louder than 100 dB can damage your dB can damage your earsears

DecibelsDecibels

Pitch- of a sound is a Pitch- of a sound is a description of how low or how description of how low or how high the sound seems to a high the sound seems to a personperson

Sound waves with a high Sound waves with a high frequency has a high pitch.frequency has a high pitch.

Sound waves with a low Sound waves with a low frequency has a low pitch.frequency has a low pitch.

PitchPitch

FemaleFemale (alto)(alto)

MaleMale (bass)(bass)

We can hear frequencies We can hear frequencies between 20 Hz and 2000 Hzbetween 20 Hz and 2000 Hz

Ultrasound- sound waves above Ultrasound- sound waves above the normal hearing rangethe normal hearing range Ultra-beyondUltra-beyond

Infrasound- sound waves below Infrasound- sound waves below the normal human range of the normal human range of hearinghearing Infra- belowInfra- below

When singing, you change When singing, you change pitch often.pitch often.

When you change pitch, you When you change pitch, you use your vocal cords.use your vocal cords.

Nestled in your vocal cords is Nestled in your vocal cords is your voice box, which is called your voice box, which is called a larynxa larynxTo sing, you contract and relax To sing, you contract and relax muscles in your throat and vocal muscles in your throat and vocal cordscords

The Doppler Effect- the change in The Doppler Effect- the change in frequency of a wave as its source frequency of a wave as its source moves in relation to an observermoves in relation to an observer

The sound waves are a change The sound waves are a change frequency which changes the pitchfrequency which changes the pitch

When a sound source moves, the When a sound source moves, the frequency of waves changes because frequency of waves changes because the motion of the source adds to the the motion of the source adds to the motion of the wavesmotion of the waves Ex. Tennis ball and wall- further you Ex. Tennis ball and wall- further you

move back the less the frequencymove back the less the frequency

Doppler EffectDoppler Effect

Groups of InstrumentsGroups of Instruments Stringed- guitar and violinStringed- guitar and violin

Vibration when a string is strummed or Vibration when a string is strummed or pluckedplucked

Pitch depends on length, thickness, Pitch depends on length, thickness, material, and how tightly its stretchedmaterial, and how tightly its stretched

Wind- brass and woodwindWind- brass and woodwind Vibrations against mouthpiece or reedVibrations against mouthpiece or reed Pitch depends on air column lengthPitch depends on air column length

Percussion- drums, cymbals, and Percussion- drums, cymbals, and xylophonesxylophones Vibrate when struckVibrate when struck Pitch depends on size, materials, and Pitch depends on size, materials, and

tension on drumheadtension on drumhead

Human EarHuman Ear

Function of your ear is to gather Function of your ear is to gather sound waves and send sound to sound waves and send sound to your brain.your brain.

The outer ear funnels sound The outer ear funnels sound waves, the middle ear transmits waves, the middle ear transmits the waves inward, and the inner the waves inward, and the inner ear converts sound waves into a ear converts sound waves into a form that travels to your brainform that travels to your brain

Outer EarOuter Ear

Outermost ear looks and acts like Outermost ear looks and acts like a funnela funnel

Ear canal- narrow region leading Ear canal- narrow region leading from the outside of the human ear from the outside of the human ear to the eardrumto the eardrum

Eardrum- small, tightly stretched, Eardrum- small, tightly stretched, drumlike membrane that vibrates drumlike membrane that vibrates when sound enterswhen sound enters

Middle EarMiddle Ear

Behind the eardrum, is the middle Behind the eardrum, is the middle ear.ear.

Three smallest bones in your body Three smallest bones in your body make up the middle ear: hammer, make up the middle ear: hammer, anvil, and the stirrupanvil, and the stirrupEardrum causes the hammer to vibrateEardrum causes the hammer to vibrateHammer causes the anvil to vibrateHammer causes the anvil to vibrateAnvil causes the stirrup to vibrateAnvil causes the stirrup to vibrate

Inner EarInner Ear

The stirrup’s vibrations transfer The stirrup’s vibrations transfer to the cochleato the cochlea

Cochlea- fluid filled sac shaped Cochlea- fluid filled sac shaped like a snail shelllike a snail shell

On the cochlea are several hairs On the cochlea are several hairs that sense the vibrations and that sense the vibrations and send the messages to the brain send the messages to the brain through the auditory nervethrough the auditory nerve

EcholocatioEcholocationn

Echolocation- use of Echolocation- use of reflected sound to reflected sound to determine distances or to locate determine distances or to locate

objectsobjects Animals use echolocation to find Animals use echolocation to find

food and avoid predatorsfood and avoid predators Bats Bats

Frequency around 100,000 HzFrequency around 100,000 Hz Dolphins Porpoises and WhalesDolphins Porpoises and Whales

Frequencies around 150,000Frequencies around 150,000

UltrasoundUltrasound

Ultrasound technologies such as Ultrasound technologies such as sonar and ultrasound images are sonar and ultrasound images are used to observe things that cannot used to observe things that cannot be seen directlybe seen directly Sonar-Sound Navigation and RangingSonar-Sound Navigation and Ranging Used to determine depth of water, Used to determine depth of water,

map the ocean floor, and locate map the ocean floor, and locate sunken shipssunken shipsTotal distance divided by twoTotal distance divided by two

UltrasoundUltrasound

Sonogram- use of reflected Sonogram- use of reflected ultrasound waves to create a ultrasound waves to create a picturepictureSee how many babies there areSee how many babies there areSee sex of babySee sex of babyPosition of a babyPosition of a babyDiagnose and treat medical Diagnose and treat medical

conditionsconditions