Sound waves and the
Ear
SoundSound travels in waves.
We “hear” vibrations of molecules.
Speed of Sound Depends on what it is traveling
through.Air 340 m/sLiquids 1400 m/sSolids 5500 m/s
Why?The more dense = more particles to
pass on energy
FrequencyHuman hearing is between 16Hz-20
000Hz (20 kHz)Dogs can hear up to 80 000 Hz and bats up to 120 000 Hz
Hearing testhttp://www.youtube.com/watch?v=4G60hM1W_mk
The Decibel ScaleA relative scale measuring the intensity
or amplitude of noiseAbove 100 dB will do damage to the
ear.Above 120 dB – pain and immediate loss of hearing
Source Intensity Level
Instant Perforation of Eardrum 160 dB
Military Jet Takeoff 140 dB Threshold of Pain 130 dB Front Rows of Rock Concert 110 dB Walkman at Maximum Level 100 dB
Large Orchestra 98 dB
Vacuum Cleaner 80 dB
Busy Street Traffic 70 dB Normal Conversation 60 dB
Whisper 20 dB
Rustling Leaves 10 dB Threshold of Hearing (TOH) 0 dB
The Ear
The Ear
Pinna orAuricle
Auditory canal
Outer Ear
Outer EarPinna or Auricle
Only visible part of ear
Shaped like a funnel
*picks up sound vibrations
Outer EarAuditory Canal
2.5 cm long*carries sound vibrations to ear
drumLined with fine hairs and glands that
secrete wax –> *prevents foreign particles from
entering ear (ex. dust)
Pinna orAuricle
Auditory canal
Outer Ear
Tympanic Membrane
Ossicles
Eustachian tube
Middle EarTympanic Membrane (eardrum)
Thin flexible membraneAbout 1 cm in diameter*moves with sound vibrations
Middle EarOssicles
3 small bonesAmplify the sound waves by 20%
Middle EarEustachian Tube
Connects middle ear to pharynxEqualizes pressure during swallowing
Pinna orAuricle
Auditory canal
Outer Ear
Tympanic Membrane
Ossicles
Eustachian tube
Semi-circular canals
CochleaVestibule
Inner EarSemi-circular canals
Filled with liquid*BALANCE when moving*
Inner EarVestibule
Links semi-circular canals to the cochleaBalance when not moving
Inner EarCochlea
Liquid filledWalls covered with hairs (auditory nerve cells)Hairs transform vibrations into a nerve impulse
Pinna orAuricle
Auditory canal
Outer Ear
Tympanic Membrane
Ossicles
Eustachian tube
Semi-circular canals
CochleaVestibule
Auditory Nerve
Auditory NerveSends information (nerve impulses) to the brain
Video clips Intro – parts - http://www.youtube.com/watch?
v=ahCbGjasm_E&feature=related
Stomp - http://www.youtube.com/watch?v=KY7_TIktQFs&feature=PlayList&p=FE42A62D04D5C9B7&playnext=1&playnext_from=PL&index=6
Hearing loss and hair cells - http://www.youtube.com/watch?v=MGj-cdn2M9o&feature=PlayList&p=FE42A62D04D5C9B7&playnext=2&playnext_from=PL&index=7