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Lesson 3 of 4
Hearing loss
In this section you will learn more about hearing loss -
its prevalence, causes and impact..


Hearing loss is the #1 disability in the world, but is also the most preventable.
According to the World Health Organization, 5.3% of the world's population have hearing impairment
Every tenth American admits that hearing loss affects his daily life.
30% of North Americans over 65 experience hearing loss. Their number increases to 90% for people over 80 years old.
3% of all children in the world have hearing impairment. In Ukraine, 2-3 children per 1000 newborns have congenital hearing defects.
25 million people would benefit from hearing aids. But only 5 million people have them.
Causes of hearing loss
Exposure of loud noise
Ear infections
Some remedies
Damaged structures of the middle and inner ear
Can be born with hearing loss (congenital)
May be acquired defect
Hearing loss may or may not be hereditary (genetic)

Types of hearing loss

There are 3 main types of hearing loss: Conductive, sensorineural and mixed.
Conductive hearing loss
Sensorineural hearing loss
Mixed hearing loss
Conductive hearing loss
Conductive hearing loss occurs when sound is not conducted efficiently in the outer ear or middle ear, or both. Injury, ear infections and congenital abnormalities are among the common causes.
Conductive hearing loss usually involves a reduction in sound level, or the ability to hear faint sounds.

Sensorineural hearing loss
Sensorineural hearing loss occurs when there is damage to the inner ear (cochlea) or to the nerve pathways from the inner ear to the brain. Sensorineural hearing loss can refer to a sensory or neural cause or both.
It not only involves a reduction in sound level, or ability to hear faint sounds, but also affects speech understanding, or ability to hear clearly.

Mixed hearing loss
A mixed hearing loss, as the name implies, is caused by a combination of both conductive and sensorineural aspects and involves the outer and/or middle ear and the inner ear.
It affects both awareness of sound and also understanding of speech.

In these images you can see microscopic scans of healthy inner ear structures on the left and damaged structures on the right. This shows the primary cause of sensorineural hearing loss.

Conductive hearing loss may be temporary and can sometimes be improved by medical/surgical treatment. In contrast, sensorineural hearing loss is usually permanent and requires non-medical intervention (like hearing instruments) for improvement.
Click the play button on the image above to see an illustration of hearing loss and the limited amount of sound that moves through the hearing system and on to the brain.
Degrees of hearing loss
The audiogram is used to determine the severity or degree of hearing loss. Most people do not hear all frequencies equally. So it is not possible to assign a single number, like a percentage, to quantify an individual's degree of impairment. Instead, general descriptive terms are used, each of which has a range.

Degrees of hearing loss
The levels of hearing loss are generally classified as mild, moderate, severe or profound.
The exact cutoff points for each category vary slightly according to different publications and different audiologists, but they are roughly as shown on the chart below.

Examples of varying degrees of hearing loss

Here you can scroll through a series of sample audiograms showing different degrees of hearing loss with descriptions for further explanation.
Dynamic range

Another important aspect of hearing loss is called 'dynamic range'. This is the range between the softest sounds one can hear and the loudest sounds one can tolerate. For those with normal hearing, this range is quite wide, usually about 120 decibels. But for people with sensorineural loss, this range is often much narrower. Sounds must be louder to be heard in the first place, but loud sounds can actually become uncomfortable sooner and cause distortion as well as discomfort. So just amplifying sound to make it louder may not be adequate or appreciated.

Knowledge check
Take a short test to see how well you have learned the information.
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What does sensorineural hearing loss mean?
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What does conductive hearing loss mean?
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Is it true or not that hearing loss is measured by percentage?
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