ANATOMY OF THE EAR

How Sound Travels

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

Then, it is directed into the outer ear canal Next, sound makes the eardrum vibrate Now, the vibration causes three tiny bones in the inner

ear to vibrate

Hammer Anvil Stirrup

Vibration of the eardrum

How Sound Travels

Finally, the vibration is transferred to the snail-shaped cochlea in the inner ear

The cochlea is lined with sensitive hair cells (cilia)

The hair cells (cilia) trigger the generation of nerve signals that are sent to the brain

Anatomy of the Ear

o Outer Ear• Pinna• Ear Canal• Outer layer of the eardum

o Middle Ear• Hammer• Anvil• Stirrup

o Inner Ear• Cochlea• Nerves• Semicircular Canals

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

Middle Ear

Hammer (Malleus)- a tiny bone that passes vibrations Anvil (Incus)- a tiny bone that passes vibrations from

the hammer to the stirrup Stirrup (Stapes)- 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)

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.

Inner Ear

Cochlea- a spiral-shaped, fluid-filled inner ear structure; it is lined with cilia (tiny hairs) that move when vibrated and cause a nerve impulse to form.

Nerves- these carry electro-chemical signals from the inner ear (the cochlea) to the brain.

Semicircular Canals- Fluid filled tubes attached to the cochlea that help us maintain our sense of balance.

Stirrup

Anvil

HammerPinna

Semicircular Canals

Nerves

Eustachian Tube

Eardrum

Outer Ear Canal

Cochlea

Hearing Loss

• There are three kinds of hearing loss:–Sensorineural–Conductive–Mixed hearing loss

Sensorineural Hearing Loss

• Also known as nerve deafness

• the inner ear or actual hearing nerve itself is damaged

• About 90% of all people with hearing impairments suffer from sensorineural hearing loss

• Most common

Conductive Hearing Loss

• outer and/or middle part of the ear fail to work properly

• Sounds become "blocked" and are not carried all the way to the inner ear (where hearing is still normal)

• Not permanent; temporary hearing loss

Mixed Hearing Loss

• A combination of a conductive and sensorineural hearing loss

• Both the middle and inner ear are involved

Causes of Conductive Hearing Loss

• a buildup of fluid in the middle ear

• wax in the ear canal

• puncturing of the eardrum

• problems or injury to the bones or membrane — which carry sound from the external ear through the middle ear to the inner ear.

Sensorineural Hearing Loss

• Usually permanent

• not medically or surgically treatable

• In most cases, the cillia or the nerves from the inner ear to the brain are irreparably damaged.

• wearing hearing aids may be of significant benefit

Causes of Sensorineural Hearing Loss

• the natural aging process

• exposure to loud noises

• infection or other disease

• a genetic disorder

• Tinnitus, or ringing in the ears, is usually associated with sensorineural hearing loss

Causes of a Mixed Hearing Loss

• This hearing disorder can also occur when a person first just has a permanent sensorineural hearing loss and then also develops a conductive hearing loss.

• For example, a person who already has a sensorineural loss gets a middle ear infection, and the two types of loss combine to create a greater hearing loss.

• Some other instances of mixed hearing loss are the result of the outer and inner ear being malformed, which causes both types of hearing 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 treatable. 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

Treatment for Mixed Hearing Loss

• With mixed hearing loss, the conductive part may be treated, but the sensorineural part is usually permanent.

Levels of Hearing Loss

• Bilateral- both ears are impaired

• Unilateral- one ear is impaired

Bilateral Hearing Loss

• Mild

• Moderate

• Severe

• Profound

Mild Hearing Loss

• A mild hearing loss may cause you to miss 25-40% of the speech signal. Usually this results in problems with clarity since the brain is receiving some sounds but not all of the information. Symptoms of mild hearing loss include problems understanding someone farther away than a normal distance for conversation, or even up close if the background environment is noisy. Weak voices are also difficult to understand for people with mild hearing losses.

Moderate Hearing Loss

• A moderate hearing loss may cause you to miss 50-75% of the speech signal. This means you would not have problems hearing at short distances and understanding people face-to-face, but you would have problems if distance or visual cues changed. Symptoms of moderate hearing loss include problems hearing normal conversations and problems hearing consonants in words

Severe Hearing Loss

• People with severe hearing loss have difficulty hearing in all situations. Speech may be heard only if the speaker is talking loudly or at close range. A severe hearing loss may sometimes cause you to miss up to 100% of the speech signal. Symptoms of severe hearing loss include inability to have conversations except under the most ideal circumstances (i.e., face-to-face, in quiet, and accompanied with speech reading).

Profound Hearing Loss

• Profound hearing loss is the most extreme hearing loss. A profound hearing loss means that you may not hear loud speech or any speech at all. You are forced to rely on visual cues instead of hearing as your main method of communication. This may include sign-language and/or speech reading (also commonly referred to as "lip-reading")

• Decibels (dB)- the intensity (volume or loudness) of a sound– A whisper is about 20 dB– loud music (some concerts) is around 80 to

120 dB– and a jet engine is about 140 to 180 dB– Usually, sounds greater than 85 dB can

cause hearing loss in a few hours; louder sounds can cause immediate pain, and hearing loss can develop in a very short time

How Hearing Loss is Measured

• Hertz- a range of frequencies• The tone of sound is measured in cycles per second (cps)

or Hertz. • Low bass tones range around 50 to 60 Hz• Shrill, high - pitched tones range around 10,000 Hz or

higher• The normal range of human hearing is about 16 Hz to

16,000 Hz• Some people can hear within a slightly higher range• Animals can hear up to about 50,000 Hz.

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 to 25dB = Normal range

• 26dB to 40 dB = Mild hearing loss

• 41 dB to 55 dB = Moderate hearing loss

• 56 dB to 70 dB = Moderately Severe hearing loss

• 71 dB to 90 dB = Severe hearing loss

• over 90 dB = Profound hearing loss

Audiogram

• Hearing loss is plotted on an audiogram

• Right ear is represented

by a red circle

• Left ear is

represented by

a blue X

Audiogram

• 10dB to 25dB = Normal hearing• 26dB to 40 dB = Mild hearing loss • 41 dB to 55 dB = Moderatehearing loss • 56 dB to 70 dB = Moderately• Severe hearing loss • 71 dB to 90 dB = Severe hearing loss• over 90 dB = Profoundhearing loss

Hertz/Decibels

Decibels

Hertz

Identify the Hearing Loss

What type of hearing loss

is it?

Normal Hearing

Moderate Loss

Mild Hearing Loss

Profound Hearing Loss

What Causes Hearing Loss?

You tell me!