A Story About the Ear
Mrs. Jameson
How Sound Travels
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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.
Semicircular Canals
Stirrup
Nerves
Anvil
Hammer
Pinna
Cochlea
Eardrum
Eustachian Tube
Outer Ear Canal
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
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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
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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
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Mild
Moderate
Severe
Profound
Mild Hearing Loss
• A mild hearing loss may cause you to miss 2540% 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 speechreading).
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
speechreading (also commonly referred to
as "lipreading")
• 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 = 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
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!