The Ear and How We Hear Notes on the EAR Ear is divided into three main sections:

The Ear and How We Hear

Notes on the EAREar is divided into three main sections:

Parts of the Ear• What do the Parts consist of?

– Outer Ear: Pinna, Outer Ear Canal, Outer Layer of Eardrum

– Middle Ear: Malleus, Incus, Stapes, Eustachian Tube

– Inner Ear: Cochlea, semicircular canals, VIII Cranial Nerve

Parts of the Outer Ear• Pinna- the visible part of the outer ear. It collects sound

and directs it into the outer ear canal.

• Ear Canal- the tube through which sound travels to the eardrum

• Outer layer of eardrum- (tympanic membrane) vibrates when sound waves reach it

• Sound goes into the pinna and travels into the outer ear canal and sound pushes against the eardrum (tympanic membrane). The sound hits the TM and makes it vibrate (moving back and forth).

Parts of the Middle Ear• Malleus (hammer)- a tiny bone that passes vibrations• Incus (anvil)- a tiny bone that passes vibrations from the hammer

to the stirrup• Stapes (stirrup)- a tiny, U-shaped bone that passes vibrations

from the stirrup to the cochlea. – This is the smallest bone in the human body. (.25 to .33 cm long)

• When the TM moves, it causes a reaction for the middle ear to move back and forth, when the three bones in the middle ear that is called ossicular chain.

• Eustachian tube- a tube that connects the middle ear to the back of the nose; it equalizes the pressure between the middle ear and the air outside.

Parts of the Inner Ear• Semicircular Canals- Fluid filled tubes attached to

the cochlea that help us maintain our sense of balance.

• Cochlea- a spiral-shaped, fluid-filled inner ear structure; it is lined with cilia (thousands of tiny hairs) that move when vibrated and cause a nerve impulse to the VIII Cranial Nerve.

• The cilia are similar to piano keys. The low sounds are found on the apex of the cochlea and high sounds are found on the base of the cochlea.

• VIII Cranial Nerve (hearing nerve)- Sends sounds to the brain to be decoded and then understood.

Stapes (Stirrup)

Incus (Anvil)

Malleus (Hammer)Pinna

Semicircular Canals

VIII Cranial Nerve

Eustachian Tube

Eardrum

Outer Ear Canal

Cochlea

Labeling the Ear

What is Sound?• Our ears hear sound, which moves in waves. • Sound can be loud or soft.

How Do We Hear?

• First, sound is collected by the pinna. (the visible part of the outer ear)

• It is directed into the outer ear canal.• Sound makes the eardrum vibrate.• The vibration causes three tiny bones in the inner ear to

vibrate Malleus, Incus & Stapes which starts the Ossicular Chain to vibrate.

• The vibration is transferred to the snail-shaped cochlea in the inner ear.

• The hair cells (cilia) trigger the generation of nerve signals that are sent to the brain through the VIII Cranial Nerve.

Types of Hearing Loss

• Three types of hearing loss:

• Conductive loss• Sensorineural loss• Mixed loss

Conductive Loss

• Conductive Loss – means something is wrong with the outer or middle ear. The outer or middle ear can be damaged.

• born without a pinna, TM or ossicular chain• damage to the outer ear canal• punctured TM• getting hit in the head• when ossicular chain begins to grow together and cannot

move easily• germs may make middle ear fill up with fluid • wax in the ear canal

Sensorineural Loss• Sensorineural Loss – means problems in the inner ear.

The nerve endings in the inner ear are damaged.

• heredity• mother may be sick during pregnancy or take medication

during pregnancy which may cause damage • born pre-mature• high fever from flu, mumps, chicken pox, and measles• getting hit in the head• loud noises• old people losing the ability to send messages to the

brain.

Mixed Hearing Loss

• Mixed Hearing Loss – means there is damage to the inner and middle, or inner and outer ear.

• Some people have both conductive and sensorineural loss.

Treatment

• Conductive hearing loss can be easier to remedy than sensorineural or mixed hearing loss.

• It is usually treatable with either medical or surgical intervention

• In cases where medical/surgical intervention is not an option, a hearing aid can be very helpful.

Treatment

• Sensorineural hearing loss is usually permanent.

• No medically or surgically treatment. In most cases, the nerves from the inner ear to the brain are irreparably damaged.

• However, most people with this hearing loss find wearing hearing aids to be of significant benefit

• Doctors can not fix damaged nerves.

Types of Hearing Loss• Bilateral- both ears are impaired• Unilateral- one ear is impaired

Levels of Hearing Loss

• Four different levels of hearing loss: –Mild–Moderate –Severe–Profound

Mild Hearing Loss

• People with mild hearing loss:

• Cannot hear soft sounds. • People may need to repeat what they have

said. • It is hard for them to hear in noisy places.

Moderate Hearing Loss

• Moderate hearing loss: means that sound must be fairly loud before a person can hear them. Speech may not sound clear to them.

Serve Hearing Loss

• Severe Hearing Loss: They cannot hear other talk. Many speech sounds are not clear to them. People with severe hearing loss hear vowels better than consonants.

Profound Hearing Loss

• Profound Hearing Loss – even very loud sounds are not heard them. People with profound hearing may hear sounds only by feeling through the body.

Identifying Hearing Loss

• Ranges have been established to help people identify how much difficulty they should expect from their hearing loss. The typical ranges for an adult are:

• 10dB - 25dB = Normal range• 25dB - 40 dB = Mild hearing loss• 40 dB - 65 dB = Moderate hearing loss• 65 dB - 90 dB = Severe hearing loss• over 90 dB = Profound hearing loss

Decibels (dB)• The loudness of sound

is measured in decibels (dB). The number tells us how soft or how loud a sound is.

• Loud sounds have high decibel number.

• Soft sounds have a low decibel number

Hertz

• Sound can be either high or low.

• The frequency of a sound tells how high or low a sound is.

• The frequency of a sound is measured in hertz (Hz).

Decibels/ Hertz

Frequency• Frequency is the number of sound waves that move

through the air each second.

• High frequency = high sound and high number of Hz. The sound waves are close together.

• Low frequency = low sound and low number of Hz. The sound waves are far apart.

• Our speech has different frequencies in it. • All vowels have low frequency sounds. • Some consonants have high frequency sounds.

(Example….K, f, s, Th)

http://www.youtube.com/watch?v=7hdoMxS5GLg7:40

Audiogram

• Hearing loss is plotted on an audiogram• Right ear is represented by a red circle• Left ear is represented by a blue X

Identify the Hearing Loss

What type of hearing loss is

it?

Normal Hearing

Moderate Hearing Loss

Mild Hearing Loss

Profound Hearing Loss

Speech Banana

Hearing Aides

• Hearing aids make sound louder. It makes the sounds loud enough for them to hear sounds they could not hear, but it doesn’t make the sound clearer.