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"The problems of deafness are deeper and more
complex, if not more important, than those of
blindness. Deafness is a much worse misfortune.
For it means the loss of the most vital stimulus-the sound of the voice that brings language, sets
thoughts astir and keeps us in the intellectual
company of man." 1 (emphasis added)
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"…after a lifetime in silence and darkness that to
be deaf is a greater affliction than to be blind...
Hearing is the soul of knowledge and information
of a high order. To be cut off from hearing is to be
isolated indeeed (emphasis added)
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Blindness cuts you off from things. But deafness
cuts you off from people.
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Most of us only have the opportunity to experience
blindness, albeit temporarily, when we close our
eyes. This enables us to appreciate in a very
limited way what it must be like to lose our
eyesight. And as with so many things in life, it is
often only by losing something important that we
can appreciate what it really means to us.
So perhaps this ability to temporarily switch off our
eyesight is the reason why so many people will
rank vision above their hearing: they've had the
opportunity to experience what they'd be missing.
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If we could switch off our hearing temporarily – as
we can our eyesight – it would very quickly give us
an insight into what our hearing actually does for
us. But because our ears are always open, our
hearing forms a seamless connection to the world
around us, and we are therefore prone to take it
for granted.
It would therefore be useful to remind ourselves
what our hearing does for us.
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Communication and inter-action (Acquisition
of normal language & speech skills).
Receiving incoming messages as a listener.
Helps to monitor once own speech as a
speaker & speech of others as listener.
Awareness and safety (Life Saving Signals).
Enjoyment and emotions (Aural Recreation).
The human ear has TWO functions
1. Hearing – The human ear helps us in
awareness, identification, discrimination and
comprehension of sound stimuli.
2. Balancing - The semicircular canals help
us maintaining the balance.
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The human ear has three main parts
Outer Ear
Middle Ear
Inner Ear
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The outer ear includes:
auricle (cartilage covered by skin placed on
opposite sides of the head)
auditory canal (also called the ear canal)
eardrum outer layer (also called the tympanic
membrane)
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Sound entering the outer ear travels through the
middle ear and causes the eardrum and ossicles
in the middle ear to vibrate. As it travels, it
amplifies (becomes louder) and changes from
air to liquid.
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The middle ear includes:
Eardrum
Cavity (also called the tympanic cavity)
Ossicles (3 tiny bones that are attached)
◦ Malleus (or hammer) – long handle attached to
the eardrum
◦ Incus (or anvil) – the bridge bone between the
malleus and the stapes
◦ Stapes (or stirrup) – the footplate; the smallest
bone in the body
The inner ear includes:
 Oval window – connects the middle ear with the inner ear
 Semicircular ducts – filled with fluid; attached to cochlea
and nerves; send information on balance and head position
to the brain
 Cochlea – spiral-shaped organ of hearing; transforms
sound into signals that get sent to the brain
 Auditory tube – drains fluid from the middle ear into the
throat behind the nose
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When the stapes moves, it pushes the oval
window, which then moves the cochlea. The
cochlea takes the fluid vibration of sounds from
the surrounding semicircular ducts and translates
them into signals that are sent to the brain by
nerves like the vestibular nerve and cochlear
nerve.
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The brain and auditory system work together to control how
we hear and how we balance ourselves. The human ear is
a complex organ and many scientists consider hearing to
be the most complex of the human senses.
Sound can be detected whether a person is on land,
underwater or in the air. Hearing is our ability to perceive
sound by detecting vibrations that travel through our
ears. The main purpose of the ear is to turn sound waves
from the air into electrical signals that are interpreted by the
brain.
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Sound: Rapid Air Waves Through the Ear
Sound travels through the auricle and the auditory canal, a short
tube that ends at the eardrum. Sound entering the outer ear
travels through the middle ear and causes the eardrum and
ossicles in the middle ear to vibrate. As it travels, it amplifies
(gets louder) and changes from air to liquid. When the stapes
moves, it pushes the oval window, which then moves the
cochlea. The cochlea takes the fluid vibration of sounds from the
surrounding semicircular ducts, translates them into signals sent
to the brain by nerves like the vestibular nerve and cochlear
nerve. The brain translates the information into recognizable
sound patterns. It is a complex process but it occurs in a splitsecond of time.
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Vocalized and Non-Vocalized Sound
The human ear can detect different tones and loudness levels,
which can help a person determine the direction of something
(locate where the sound comes from), and helps to pick out
specific sounds despite lots of background noise. Specifically,
when someone is speaking, the sounds may be vocalized or
non-vocalized.
Vocalized Sound: Vowels
Vocalized sounds require a combination of air passing through
the vocal cords and mouth shapes.
When a person is speaking, the vocal cords are in
vibration. There is no closure of the throat or mouth with these
sounds. And, in almost all languages, words must contain at
least one vowel.
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Non-Vocalized Sound: Consonants
Non-vocalized sounds are created strictly from
mouth shapes. Lipreading is the process of visually
detecting non-vocalized sounds.
When a person is speaking, the quietest sounds are
those that are actually easier to detect
visually. When a person can see someone speak,
they can understand him or her better. This
combination of seeing what is heard contributes to a
better sense of understanding.
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Auditory Pathways
The auditory pathways begin in the nerve fibers in
the inner ear, where sound waves get converted into
nerve impulses. These impulses then travel via the
auditory nerve to the highest cerebral levels in the
cortex of the brain.
Definition
1.Hearing impairment may be defined as inability of a
person to perform day to day communication with or
without amplification.
2. According to PWD (Persons With Disability- Equal
opportunities, protection of rights & full participation ) Act
1995 Hearing disability means loss of 60 decibels or more
in the better ear in the conversational range of frequencies.
How we hear
(a) Pinna
 (b) Ear canal
 (c) Eardrum
 (d) 3 smallest bones in the body
 (e) Cochlea
 (f) Auditory nerve
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The hearing loss can be classified on
the following basis:
1) Onset of hearing loss
2) Site of lesion
3) Degree of hearing loss
 Hearing
loss/deafness in early
childhood/since birth {Prelingual deafness}
… Severe Speech & Language Deficits
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Deafness Acquired after speech & language
development {Post-lingual Deafness}
… Deterioration in speech because of
difficulty in monitoring one’s own speech.
1. Conductive hearing loss
2. Sensori - neural hearing loss
3. Mixed hearing loss
4. Auditory processing disorder
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0-15
16-25
26-40
41-55
56-70
71-90
>90
Normal Hearing
Minimal hearing loss
Mild hearing loss
Moderate hearing loss
Moderately severe hearing loss
Severe hearing loss
Profound hearing loss
How we hear
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A loss of sensitivity
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Auditory nervous system pathology
Time of onset
 Congenital:
 Acquired:
 Adventitious:
present at birth
obtained after birth
acquired after birth
Time Course
 Acute:
 Chronic:
 Sudden:
 Gradual:
sudden onset/short duration
long duration
rapid onset
changes slowly over time
Time Course
 Temporary:
 Permanent:
 Progressive:
 Fluctuating:
limited duration
irreversible
advancing
changes in degree
over time
Number of Ears Involved
 Unilateral:
 Bilateral:
Just one
Both
“The ear is not as sensitive as normal in
detecting sound”
 Types:
 Conductive
 Sensorineural
 Mixed
“Caused by an abnormal reduction or
attenuation of sound as it travels from the
outer ear to the cochlea”
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Conductive hearing loss is characterized by an obstruction to
air conduction that prevents the proper transmission of sound
waves through the external auditory canal and/or the middle ear.
It is marked by an almost equal loss of all frequencies. The
auricle (pinna), external acoustic canal, tympanic membrane, or
bones of the middle ear may be dysfunctional. Conductive
hearing loss may be congenital or caused by trauma, severe
otitis media, otosclerosis, or atresia of the ear canal. Some
conductive hearing loss can be treated surgically with
tympanoplasty or stapedectomy, and the use of hearing aids
and assistive listening devices may also be beneficial.
An audiogram of a bilateral conductive
hearing loss
Differences in the air-bone gap across different
types of hearing loss
“Caused by a failure in the cochlea to
transduce the sound from the middle ear
to neural impulses in the VIII Nerve.”
Implications include:
A
reduction in the sensitivity of the receptor
cells in the cochlea
 A reduction in the frequency resolving
power of the cochlea
 A reduction in the dynamic range of the
system
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Sensorineural hearing loss occurs when the sensory
receptors of the inner ear are dysfunctional. Sensorineural
deafness is a lack of sound perception caused by a defect in the
cochlea and/or the auditory division of the vestibulocochlear
nerve. This type of hearing loss is more common than
conductive hearing loss and is typically irreversible. It tends to
be unevenly distributed, with greater loss at higher frequencies.
Sensorineural hearing loss may result from congenital
malformation of the inner ear, intense noise, trauma, viral
infections, ototoxic drugs (e.g., cisplatin, salicylates, loop
diuretics), fractures of the temporal bone, meningitis, ménière's
disease, cochlear otosclerosis, aging (i.e., presbycusis), or
genetic predisposition, either alone or in combination with
environmental factors.
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Many patients with sensorineural hearing loss can be
habilitated or rehabilitated with the use of hearing aids.
Patients with profound bilateral sensorineural hearing loss
(e.g., at least 90 dB) who derive no benefit from conventional
hearing aids may be appropriate candidates for the cochlear
implant device, which bypasses the damaged structures of
the cochlea and stimulates the function of the auditory nerve.
An audiogram of a bilateral sensorineural
hearing loss
Differences in the air-bone gap across different
types of hearing loss
“A loss with both a conductive and sensorineural
component.”
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Individuals with mixed hearing loss have both
conductive and sensory dysfunction. Mixed
hearing loss is due to disorders that can affect the
middle and inner ear simultaneously, such as
otosclerosis involving the ossicles and the
cochlea, head trauma, middle ear tumors, and
some inner ear malformations. Trauma resulting in
temporal bone fractures may be associated with
conductive, sensorineural, and mixed hearing
loss.
An audiogram of a bilateral mixed hearing loss
Differences in the air-bone gap across
different types of hearing loss
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Auditory Processing Disorder (APD) is a deficit in
neural processing of auditory stimuli that is not due to
higher order language, cognitive, or related factors.
However, APD may lead to or be associated with
difficulties in higher order language, learning, and
communication functions. This type of auditory
problem affects more complex auditory processes,
such as understanding speech when there is
background noise. The results of hearing sensitivity
and physiological tests, such as otoacoustic emissions
(OAE) and auditory brainstem response (ABR) are
normal in children with a central auditory disorder.
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A loss of sensitivity
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Auditory nervous system pathology
Causes:
 Disease
 Disordered
auditory nervous system
development
Kinds:
Retrocochlear disorders
 Central auditory processing disorders
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Auditory Characteristics:
 Reduced
ability to understand speech in
a noise background
 Problems understanding speech with
reduced redundancy
 Problems with localization and
lateralization
 Problems processing normal or altered
temporal cues
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Deaf/Deafness refers to a person who has a profound
hearing loss and uses sign language.
Hard of hearing refers to a person with a hearing loss
who relies on residual hearing to communicate through
speaking and lip-reading.
Hearing impaired is a general term used to describe
any deviation from normal hearing, whether permanent
or fluctuating, and ranging from mild hearing loss to
profound deafness.
Residual hearing refers to the hearing that remains
after a person has experienced a hearing loss. It is
suggested that greater the hearing loss, the lesser the
residual hearing.
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Conductive hearing loss is characterized by an
obstruction to air conduction that prevents the
proper transmission of sound waves through the
external auditory canal and/or the middle ear. It is
marked by an almost equal loss of all frequencies.
The auricle (pinna), external acoustic canal, tympanic
membrane, or bones of the middle ear may be
dysfunctional. Conductive hearing loss may be
congenital or caused by trauma, severe otitis media,
otosclerosis, neoplasms, or atresia of the ear canal.
Some conductive hearing loss can be treated
surgically with tympanoplasty or stapedectomy, and
the use of hearing aids and assistive listening devices
may also be beneficial