Transcript Hearing Conservation Update for 2004

Preventing Hearing Loss
Anatomy of the Ear
• Outer ear - includes the part you can see. Its shape helps to collect
sound waves. A tube leads inward to the eardrum.
• Middle ear - separated from the outer ear by the eardrum. The middle
ear contains three tiny bones called the malleus (hammer bone), the
incus (anvil bone) and the stapes (stirrup bone). These bones amplify
the movement of the eardrum produced by sound waves. The
Eustachian tube attaches the middle ear to the back of the throat and
helps to equalize air pressure.
• Inner ear - sound waves are picked up by a little spiral-shaped organ
called the cochlear. Hairs on the cochlear sense the vibration and pass
the message - interpreted into electrical impulses - on to the brain via
the cochlear nerve.
Types of Hearing Loss
• Sensori neural hearing loss
• Conductive hearing loss
Types of Hearing Loss
SENORI NEURAL
• Sensori neural hearing loss is the result of
damage to the inner ear and accounts for over 90%
of hearing loss in adults. This type of hearing loss
is generally permanent.
• Sensori neural hearing loss is irreversible and
unnecessary is caused by loud, sudden noises and
are more damaging to hearing than regular and
extended exposure to loud sounds over a period of
time.
Causes of Hearing Loss
SENORI NEURAL
• Deterioration of hair cells due to exposure to loud
sounds or aging
• Deterioration of nerves pathways that transmit
signals to the brain, most commonly caused by a
tumor pinching the nerves
• Trauma to the head
• Infection that reaches the inner ear
• Heredity
Two Types of Hearing Loss
Sensori neural loss
Types of Hearing Loss
CONDUCTIVE
• Conductive hearing loss occurs when there
is damage or blockage in the outer or
middle ear, preventing sound from traveling
normally through the ear canal to the inner
ear. This type of hearing loss can often be
corrected.
Causes of Hearing Loss
CONDUCTIVE
• Fluid build up, often due to ear infection
• Ear wax
• Perforated ear drum
Two Types of Hearing Loss
Conductive loss
Factors That Affect Both Types
• Type of Noise – continuous, intermittent, impact,
high or low frequency
• Intensity of Noise – level of loudness
• Duration of Exposure – length of time subjected to
noise, and over time how often subjected to noise
• Type of Noise Environment – enclosed, open,
reflective surfaces
• Distance from Ears to the Source of Noise
Factors That Affect Both Types
• Physical position/posture relative to the noise
source
• Age of listener
• Individual Susceptibility
• General Health of listener
• Number of other Exposures to Noise – at home, in
the workplace, during recreational/leisure
activities, etc.
Ear Disorders
• Tinnitus - noises or ringing in the ears or
head
• Meniere's disease - symptoms may include
vertigo (dizziness), tinnitus, hearing loss
and nausea
• Acoustic Neuroma - tumors on the acoustic
nerve.
Noise Exposure
• Excessive noise levels over a long period of time
will damage your hearing so gradually and
painlessly that you may not notice the minor
deterioration from one day to the next. The parts
of the ear that process high frequency sounds are
usually the first to be affected. The degree of loss
depends on the loudness of the noise and your
level of exposure.
Noise Exposure
• Sudden explosive sounds, such as gunshots, can
cause immediate damage. Some people exposed to
excessive noise develop tinnitus, which is
described as a constant ringing sound. For most
cases of noise-induced hearing loss, there is no
cure. Hearing aids only amplify sounds, and can't
replace normal hearing.
Noise Exposure
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Apart from damage to hearing, exposure to constant and
excessive noise can cause other health problems,
including:
Headache
Elevated blood pressure
Fatigue
Irritability
Digestive disorders
Increased susceptibility to colds and other minor infections
Sample Sound Levels
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Normal conversation - 60 dB
Ringing telephone - 80 dB
Hair dryer; power lawnmower - 90 dB
Belt sander - 93 dB
Tractor - 96 dB
Hand drill - 98 dB
Impact wrench - 103 dB
Bulldozer; spray painter - 105 dB
Sample Sound Levels
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Continuous miner - 108 dB
Chain saw - 110 dB
Hammer drill - 114 dB
Pneumatic percussion drill - 119 dB
Ambulance siren - 120 dB
12-gauge shotgun - 165 dB
Rocket launch - 180 dB
Causes of Hearing Loss
• Hereditary disorders - some types of deafness
are hereditary, which means parents pass on
flawed genes to their children. In most cases,
hereditary deafness is caused by malformations of
the inner ear.
• Genetic disorders - genetic mutations may
happen at conception
Causes of Hearing Loss
• Prenatal exposure to disease - a baby will be born deaf or
with hearing problems if they are exposed to certain
diseases, including rubella (German measles), influenza
and mumps. Other factors that are thought to cause
congenital deafness include exposure to methyl mercury
and drugs such as quinine.
• Noise - loud noises (such as gun shots, firecrackers,
explosions and rock concerts) can damage the delicate
mechanisms inside the ear. If you are standing next to
someone, yet have to shout to be heard, you can be sure
that the noise is loud enough to be damaging your ears.
Causes of Hearing Loss
• Trauma - such as perforation of the eardrum, fractured
skull or changes in air pressure (barotrauma).
• Disease - certain diseases can cause deafness including
meningitis, mumps, and chicken pox. A severe case of
jaundice is also known to cause deafness.
• Other causes - other causes of deafness include Meniere's
disease and exposure to certain chemicals.
Age Related Loss
• Our hearing gradually becomes less acute as we
age. This is normal, and rarely leads to deafness.
Age-related hearing loss (presbycusis) typically
begins with the loss of higher frequencies, so that
certain speech sounds - such as 's', 'f' and 't' - end
up sounding very similar. This means the older
person can hear, but not always understand. For
example, the words 'see' and 'tea' might sound the
same.
Severity of Hearing Loss
• Mild (21-45dB) - soft sounds may be difficult to
distinguish.
• Moderate (46-60dB) - conversational speech is hard to
hear, especially if there is background noise (such as a
television or radio).
• Moderately severe (61-75dB) - it is very difficult to hear
ordinary speech.
• Severe (76-90dB) - conversational speech can't be heard.
• Profound (91dB) - almost all sounds are inaudible. Most
people with profound hearing loss benefit from a hearing
aid, while some don't.
Causes of Temporary Deafness
• Wax - the ear canal secretes a waxy substance that helps to protect and
lubricate the tissues. A build-up of wax can block the ear canal, leading
to short term conductive deafness.
• Foreign object - similarly to ear wax, a foreign object stuck inside the
ear canal (such as the tip of a cotton bud) can temporarily cause
hearing loss.
• Excess mucus - the common cold, a bout of flu, hay fever or other
allergies can cause an excess of mucus that may block the Eustachian
tubes of the ear.
• Ear infections - including infections of the outer ear and infections of
the middle ear where fluid and pus don't allow the full conduction of
sound.
• Drugs - certain drugs, including aminoglycosides and chloroquine, can
cause temporary deafness in susceptible people.
Deafness
• The ear is our organ of hearing. At around 20 years of age,
our hearing starts a gradual decline. Higher frequencies are
usually the first to go. This age-related hearing loss is
normal and doesn't lead to total loss of hearing. Deafness
can range from mild to profound and is caused by many
different events including injury, disease and genetic
defects. There are various ways to categorize deafness. The
two main types of deafness are conductive deafness and
nerve deafness. Deafness at birth is known as congenital
deafness, while deafness that occurs after birth is called
adventitious deafness. The most common cause of
adventitious deafness is noise, which accounts for over one
quarter of people affected by hearing loss.
Deafness
• Conductive deafness is caused by the failure of the
three tiny bones inside the middle ear to pass
along sound waves to the inner ear. Another
common cause of conductive deafness is the
failure of the eardrum to vibrate in response to
sound waves. A build-up of fluid in the ear canal,
for example, could dampen the movement of the
eardrum. In many cases, treatment is available for
conductive deafness and normal hearing will
return.
Deafness
• Nerve deafness is caused by disease, trauma or
some other disruptive event targeting the cochlear
nerve. The rest of the ear - including the tiny
bones and eardrum - may be working, but the
electrical impulses aren't able to reach the brain. In
other cases, the problem is in the brain itself,
which can't 'translate' the messages from the
cochlear nerve. Most cases of nerve deafness don't
respond to treatment.