Physical Physical ScienceScience

Chapter 8Chapter 8SoundSound

SoundSound Sounds are longitudinal waves that require a Sounds are longitudinal waves that require a

medium to travel caused by the vibrations of an medium to travel caused by the vibrations of an object.object.

Speed of Sound – on average:Speed of Sound – on average: Air is 767 mph (343 m/s) – about 1 mile every 5 Air is 767 mph (343 m/s) – about 1 mile every 5

secsec Water is 3,315 mph (1,482 m/s)Water is 3,315 mph (1,482 m/s) Steel is 13,330 mph ( 5,960m/s)Steel is 13,330 mph ( 5,960m/s)

The speed of sound depends on the elasticity, The speed of sound depends on the elasticity, density and temperature of the medium.density and temperature of the medium.

Sonic Boom follows

Speed of SoundSpeed of Sound Speed of SoundSpeed of Sound: depends on the : depends on the elasticityelasticity, , densitydensity and and

temperaturetemperature ElasticityElasticity – – the ability of an object to bounce back to its original the ability of an object to bounce back to its original

shape. Sound travels faster in more elastic objects. Typically gasses shape. Sound travels faster in more elastic objects. Typically gasses are the least elastic, liquids are next and solids are the most elastic.are the least elastic, liquids are next and solids are the most elastic.

DensityDensity – – generally speaking, in material of the same state of generally speaking, in material of the same state of matter (solid, liquid or gas) the matter (solid, liquid or gas) the denser the medium denser the medium the the slowerslower the the sound travels. Sound travels slower in lead than it does in steel.sound travels. Sound travels slower in lead than it does in steel.

TemperatureTemperature – – generally speaking the generally speaking the higher the temperature higher the temperature the the fasterfaster the speed of sound. the speed of sound.

Breaking the Sound Breaking the Sound BarrierBarrier

Chuck Yeager Chuck Yeager – – first man to fly faster than first man to fly faster than the speed of soundthe speed of sound

Andy Green Andy Green – – first man to drive a land first man to drive a land vehicle faster than the speed of sound.vehicle faster than the speed of sound.

October 14, 1947 – in X1 “Glamorous

Glennis”

October 15, 1997 – in SuperSonic Car

“Thrust SSC”763 MPH

Properties of SoundProperties of Sound IntensityIntensity – – the amount of energy the wave carries the amount of energy the wave carries

per second per meter squaredper second per meter squared

intensity = Watts / mintensity = Watts / m22

LoudnessLoudness – – sound level is measured in sound level is measured in decibelsdecibels (dB) (dB)

Frequency & PitchFrequency & Pitch FrequencyFrequency – the number of vibrations per second – the number of vibrations per second

Human Hearing – between 20 Hz – 20,000 HzHuman Hearing – between 20 Hz – 20,000 Hz Below 20 Hz is called infrasoundBelow 20 Hz is called infrasound Above 20,000 Hz is called ultrasoundAbove 20,000 Hz is called ultrasound

PitchPitch - dependent of frequency - dependent of frequency high frequency yields high pitch soundshigh frequency yields high pitch sounds Low frequency yields low pitchLow frequency yields low pitch

ResonanceResonance – when the frequency of sound – when the frequency of sound matches the natural frequency of an objectmatches the natural frequency of an object

Tacoma Narrows Bridge collapse

A Perfect Matching or A Perfect Matching or a Bunch of “Fill-in-the-a Bunch of “Fill-in-the-

Blanks”Blanks”

Hearing – Human SoundHearing – Human SoundNeed to know these structures & their function: Outer Ear, Need to know these structures & their function: Outer Ear,

Middle Ear, Inner Ear, Pinna, Auditory canal, Tympanum, Middle Ear, Inner Ear, Pinna, Auditory canal, Tympanum, Malleus, Incus, Stapes, Oval Window, Cochlea, Auditory Malleus, Incus, Stapes, Oval Window, Cochlea, Auditory Nerve, Semicircular Canals, Eustachian TubeNerve, Semicircular Canals, Eustachian Tube

Outer EarOuter Ear PinnaPinna- (the ear flap aka - (the ear flap aka

auricleauricle), used to focus ), used to focus the sound waves into the sound waves into the ear canalthe ear canal

External Auditory External Auditory MeatusMeatus – the “hole – the “hole through the temporal through the temporal bone that opens the bone that opens the space for the ear canal, space for the ear canal, the middle & inner earsthe middle & inner ears

Auditory CanalAuditory Canal – (ear – (ear canal), focuses the canal), focuses the sound onto the ear sound onto the ear drumdrum

Tympanic membraneTympanic membrane – – (ear drum), end of the (ear drum), end of the outer ear, beginning of outer ear, beginning of the middle ear. Sound the middle ear. Sound starts the ear drum starts the ear drum vibrating.vibrating.

Middle EarMiddle Ear Tympanic membraneTympanic membrane

vibrates vibrates Causing the 3 Causing the 3

smallest bones in to smallest bones in to vibrate, one after the vibrate, one after the nextnext MalleusMalleus (hammer) (hammer)

is touching the ear is touching the ear drum & vibrates firstdrum & vibrates first

Next is the Next is the IncusIncus (anvil) (anvil)

Last is the Last is the StapesStapes Eustachian TubeEustachian Tube: :

tube that connects tube that connects the middle ear w/ the the middle ear w/ the pharynx. This allows pharynx. This allows the pressure on both the pressure on both sides of the ear drum sides of the ear drum to equalize.to equalize.

Inner EarInner EarThe The StirupStirup vibrates the vibrates the oval windowoval window of the of the cochleacochlea. Cochlea is a . Cochlea is a long fluid filled tube, folded in half and the coiled up like a snail long fluid filled tube, folded in half and the coiled up like a snail shell. The entire inner surface is lined w/ shell. The entire inner surface is lined w/ cillia.cillia. Attached to the Attached to the cillia is a cillia is a nerve fibernerve fiber. Once cillia are vibrated, the attached . Once cillia are vibrated, the attached nerves are stimulated & send signal to the brain.nerves are stimulated & send signal to the brain.BalanceBalance is achieved by the is achieved by the

semicircular canalssemicircular canals. 3 canals in 3 . 3 canals in 3 different planes are able to different planes are able to determine body position in spacedetermine body position in space

That’s all Folks …That’s all Folks …Learn it…Learn it…Live it…Live it…

Love it !!!Love it !!!