sound waves and the ear

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