Hearing: How do we hear?

Our Essential Questions

• What are the major parts of the ear?

• How does the ear translate sound into neural impulses?

Sound

• What part of the brain?

• Sound comes in waves

• Vibration

Pitch

• A sound’s highness or lowness

• Dependent on the frequency of the sound wave– the more “waves per second” the higher the

frequency or pitch

• Measured as hertz (Hz)

Hertz (Hz)

• Measure of the number of sound wave peaks per second; measures frequency

• Determines the pitch of the sound

• Human hearing: 20 Hz - 20,000 Hz

What pitch can you hear?

http://journal.plasticmind.com/ears/mosquito-tone-or-how-to-tell-youre-a-youngun/

Decibel (dB)

• A measure of the height of the sound wave

• Loudness of the sound• Amplitude

What are good sounds versus bad?

• What volume do you think is okay?

• Not good, not bad?

• Bad?

Hearing: The Structure of the

Auditory System

Divisions of the Ear

• Ear’s structure can be divided into:

–The outer ear

–The middle ear

–The inner ear

Break It Down

• Sound waves are collected in the outer ear, amplified in the middle ear, and transduced, in the inner ear.

Divisions of the Ear

The outer ear collects sound

Parts of the Outer Ear – Pinna

•The visible part of the outer ear.•collects sound and directs it to auditory canal

Parts of the Ear – Sound Waves

• The opening, tunnel that sound waves travel through

• Ends at the eardrum

Parts of the Outer Ear – Auditory Canal

Parts of the Outer Ear – Auditory Canal

Divisions of the Ear

The middle ear amplifies sound

Parts of the Middle Ear - Eardrum• AKA tympanic membrane• Thin membrane that vibrates when

sound waves reach it• Transfers sound vibration from the

air to the tiny bones of the middle ear

• Damage?

Parts of the Middle Ear – Tympanic Membrane

Parts of the Middle Ear - Ossicles

• 3 tiny bones that transfer sound waves from the eardrum to the cochlea

• Hammer, anvil and stirrup– Fun fact: the stirrup is the smallest

bone in the human body – only .25 cm

Parts of the Middle Ear - Occicles

Divisions of the Ear

The inner ear transduces sound

Parts of the Inner Ear - Oval Window

• Intersection of the middle ear with the inner ear

• Touches the stirrup • As the oval window vibrates, the

fluid in the cochlea vibrates• From eardrum oval window,

sound is amplified 20 times

Parts of the Inner Ear – Oval Window

Parts of the Inner Ear - Cochlea

• A hearing organ where sound waves are changed into neural impulses (transduction)

• The major organ of hearing• Filled with fluid; a snail shaped

body tube

Parts of the Ear - Cochlea

Parts of the Inner Ear - Hair Cells• The receptor cells …what do they do?

• Transduction!

Parts of the Inner Ear - Hair Cells

Parts of the Inner Ear - Auditory Nerve

• carries sound information from the ears to the brain

• Like the optic nerve

Parts of the Inner Ear – Auditory Nerve

Hearing - Review

• Sound is collected by pinna• Goes through the ear canal to the

eardrum• Eardrum changes sound vibrations• Vibrations go from middle ear

inner ear via oval window

Hearing - Review

• Here vibrations neural impulses so that the brain can read / interpret the sound

• What are the receptors cells for hearing?

Problems with hearing• Conduction deafness (middle

ear damage)

• Nerve deafness (hair cell or auditory nerve damage)

Problems with hearing

•http://www.youtube.com/watch?v=lioNIbtFxSY&feature=related

• Cochlear Implants:

• http://www.youtube.com/watch?v=4Avc3nNFxIA&feature=related

Hair Cell Loss

• Read the article “How the iPod and other audio devices are destroying your ears”

• Answer the review questions at the end

Localization of Sound

• Locating where sound is originating from

• Done through two cues:

–Which ear hears the sound first?

–Which ear hears the sound louder?

Localization of Sound

YOU Break It Down This Time

• Sound waves are ______ in the outer ear, _______ in the middle ear, and ________, in the inner ear.

• Is there another sense in your ear?

Vestibular Sense• body orientation and balance

• Receptor cells: semicircular canals, hair cells in inner ear

• Parietal lobes

• Motion sickness = overstimulation

Parts of the Ear – Semicircular Canals

Parts of the Ear – Semicircular Canals

Semicircular canal

• What situations will affect the semicircular canal?

Let’s Process

• Get a piece of paper• Trace the ear• Label as much as you can by your self

– 60 seconds• Get with a partner – fill in the rest • Together, briefly describe how sound

is changed into neural impulses

• UKULELE