hearing loss and correction

8/3/2019 Hearing Loss and Correction

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HEARING LOSS AND CORRECTION


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HEARING

It is one of the traditional five senses. The inabilityto hear is called deafness.

In humans and other vertebrates, hearing is

performed primarily by the auditory system:vibrations are detected by the ear and transducedinto nerve impulses that are perceived bythe brain (primarily in the temporal lobe).Like touch, audition requires sensitivity to the

movement of molecules in the world outside theorganism. Both hearing and touch are types ofmechanosensation.


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Hearing Loss

one of its common cause is aging, calledpresbycusis ( literally elder hearing)

other causes are trauma (sudden injury),

prolonged exposure to high sound levels, disease

and congenital birth defect.

one of its basic types is conductive hearing loss

caused by defects in the structure that conduct

sound to the inner ear.

another type is neural hearing loss(sometimescalled sensorineural, for sensory and neural)

results from damage to the cochlea or neurons that

send sound information to the brain and difficult to

correct.


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considered severe when it interferes with a

persons ability to understand conversationalspeech.

in presbycusis, hearing is normal at low

frequencies but falls of rapidly at higher

frequencies. This person should not havemuch difficulty understanding conversational

speech but is likely to have difficulty if the

losses worsen.

Noise- induced hearing loss often damages

hearing only over a narrow range of

frequencies


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Hearing Test is a step in evaluating hearing loss todetermine the severity of a hearing loss and to aid in

determining its type and correct ability.

most common testing procedure is to place the

patient in a soundproof room ad ask him or her to signal

when a sound becomes audible.

ear is tested individually using a headset.range of discrete frequencies is tested typically 250,

500, 1000, 2000, and 8000 Hz .

if hearing loss is detected, second test is

administered using bone conduction of sound.


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in bone conduction test, a probe is placed against the skull

behind the ear and sound vibrations of various frequencies

and intensities are sent to the inner ear.

bone conduction test bypass the outer and middle ear

structures; if hearing is significantly better by bone

conduction, then the hearing loss is conductive rather then

neural.

the results of this test can be graph by the use of

audiogram.

in audiogram, hearing threshold levels graphed in the

vertical axis are he number of decibels above the normal

threshold needed to be barely audible to the person tested.

The open brackets are test results using bone conduction,

and the circles are results using air conduction.


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it is instructive to note the difficulty of making precise

hearing measurements and also to comment on what

constitutes a severe hearing loss before examining thehearing test results because it suffer from a number of

difficulties.

attenuation of sound in bone varies with frequency and

differs from attenuation of air and this makes it difficult

to obtain precise intensities.

these difficulties are overcome by careful and

consistent technique and by putting noise into the ear

that is not being tested(called masking).

air conduction test are more accurate because air

attenuation is negligible for all frequencies and the

equipment can be calibrated more easily.


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TREATMENTS

one possible treatment is the use of

hearing aid that sends sound to inner ear

by bone rather than air conduction.

another treatment may be used,depending on what part of the

conduction mechanism is affected and

how it is affected.

surgery and other amplification through

air are other possibilities


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An audiogram is a standard way of

representing a person's hearing loss. Most

audiograms cover the limited range 100Hzto 8000Hz (8kHz) which is most important

for clear understanding of speech, and they

plot the threshold of hearing relative to a

standardized curve that represents 'normal'hearing, in dBHL. They are not the same as

equal-loudness contours, which are a set of

curves representing equal loudness at

different levels, as well as at the threshold

of hearing, in absolute terms measured indB SPL (sound pressure level).


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Audiograms are set out with

frequency in hertz (Hz) on thehorizontal axis, most commonly on a

logarithmic scale, and a lineardBHL

scale on the vertical axis. Normal

hearing is classified as being between-10dBHL and 15dBHL, although 0dB

from 250Hz to 8kHz is deemed to be

'average' normal hearing.


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Hearing thresholds of humans and othermammals

can be found by using behavioral hearing tests or

physiological tests. An audiogram can be obtained

using a behavioral hearing test called Audiometry. For

humans the test involves different tones being

presented at a specific frequency (pitch) and intensity

(loudness). When the person hears the sound they

raise their hand or press a button so that the tester

knows that they have heard it. The lowest intensitysound they can hear is recorded. The test varies for

children, their response to the sound can be a head

turn or using a toy. The child learns what they can do

when they hear the sound, for example they are

taught that when they heard the sound they can put a

toy man in a boat. A similar technique can be used

when testing some animals but instead of a toy, food

can be used as a reward for responding to the sound.

Physiological


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tests do not need the patient to

respond (Katz 2002). For examplewhen performing the brainstem

auditory evoked potentials the

patients brainstem responses are

being measured when a sound is

played into their ear.

Hazel Anne bangiban

Grethel Jane V. Banes

hearing loss and correction

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