“More
than 120 million people in the world have a disabling hearing
impairment.”—World Health Organization.
OUR ability to hear is a gift to be
treasured. As we age, though, our hearing progressively diminishes. Modern
society, with the many and varied sounds and noises it generates, seems to have
accelerated this process. A senior scientist at the Central Institute for the
Deaf, in St. Louis, Missouri, U.S.A., noted: “About 75 percent of
hearing loss in the typical American is caused not by the aging process alone
but by what you’ve done to your ears throughout your lifetime.”
Intense, brief exposure to loud sounds can be
harmful to the sensitive structures in the inner ear. More often, though,
hearing loss is a result of “the cumulative effect of noisy jobs, noisy
hobbies, noisy recreational activities,” said hearing specialist
Dr. Margaret Cheesman. What can you do to protect your hearing? To find
the answer, it is helpful to know something about how your sense of hearing
functions.
The Sounds We Hear
Our living environment seems to be getting
louder. Daily many are battered by sounds of varying intensities ranging from
the noise of cars, buses, and trucks in the streets to the racket of power
tools in the workplace.
Sometimes we add to the problem by turning up
the volume. One popular way of listening to music is through headphones
attached to a portable CD or cassette player. According to Marshall Chasin,
cofounder of the Musicians’ Clinics of Canada, surveys conducted in Canada and in
the United States indicate that youths are increasingly suffering loss of
hearing caused by the use of headphones with the volume turned up.
But what is too loud? Sound is characterized
in three ways—by duration, by frequency, and by amplitude. Duration simply
refers to the length of time a sound is heard. A sound’s frequency, or pitch,
is described in cycles per second, or hertz. The range of audible frequency for
normal, healthy hearing is from 20 to 20,000 cycles per second.
A sound’s amplitude, or strength, is measured
in units called decibels (dB). Normal conversation has a sound level of
approximately 60 decibels. Audiologists say that the longer you are exposed to
anything louder than 85 decibels, the greater will be the eventual loss of
hearing. The louder the sound, the faster the damage to hearing. A Newsweek
magazine report noted: “Your ear can safely handle two hours with a power drill
(100 dB), but not more than 30 minutes in a noisy video arcade (110 dB). Every
10-decibel increase on the sound scale represents 10 times more ear-battering
noise.” Tests confirm that sound becomes painful at approximately 120 decibels.
Incredibly, some home stereo equipment can produce sound at more than 140 decibels!
To help you understand why loud sounds can
damage your hearing, let us consider what happens when sound waves reach your
ears.
How Our Hearing
Functions
The shape of the fleshy part of the outer
ear, called the auricle, or pinna, is designed to collect sound waves and
direct them into the ear canal, where they soon reach the eardrum. At this
point the sound waves cause the eardrum to vibrate, and the eardrum, in turn,
causes the three bones in the middle ear to vibrate. Next, the vibrations are
transmitted into the inner ear, a fluid-filled sac encased in bone. Here the
vibrations move through the fluid in the cochlea, the snail-shaped hearing part
of the inner ear that contains the hair cells. The fluid in the cochlea
triggers the top portion of the hair cells to produce readable nerve impulses.
These impulses are then transmitted to the brain, where they are decoded and
interpreted as sound.
The limbic system helps the brain decide
which sounds to pay attention to and which to dismiss. For instance, a mother
may not consciously hear the normal sounds of a child at play, but she will
respond instantly to a cry of alarm. Hearing with two ears enables us to hear
in stereo, which is very useful. It allows us to identify where the sounds are
coming from. Yet, when a sound consists of speech, the brain can only
understand one message at a time. “This is why,” says the book The Senses,
“when listening to someone while talking on the telephone, people cannot
readily take in what the person next to them is saying.”
How Noise Damages Our
Hearing
To visualize how loud sounds can damage our
hearing, consider the following analogy. One occupational safety report
compares the hair membranes in the inner ear to wheat in a field and the sound
entering the ear to the wind. A gentle breeze, like a low level sound, will
move the tops of the wheat, but the wheat is not damaged. Increased wind
velocity, however, will increase the stress on the wheat stalk. A sudden,
extremely high wind or continuous exposure to lower winds over a long period of
time may damage the stalk beyond repair and cause it to die.
It is similar with noise and the tiny,
delicate hair cells in the inner ear. An instant loud blast can tear the
tissues of the inner ear and leave scars that cause permanent hearing loss. In
addition, prolonged dangerous noise levels can permanently damage the delicate
hair cells. Once damaged, they cannot regenerate. The accompanying result may
be tinnitus—a buzzing, ringing, or roaring in the ears or head.
Protect and Prolong
Your Hearing
Although heredity or some unforeseen accident
may result in hearing loss, we can take precautions to protect and prolong our
precious sense of hearing. It is good to learn in advance about potential
hearing hazards. As one audiologist said, “waiting for a problem to arise
before taking action is like applying the suntan lotion after you’ve been
burned.”
Often it is a matter of how we listen
and not so much what we listen to. For example, if you use stereo headphones,
you may want to set the volume at a level low enough for you to be able to hear
sounds around you. If your car or home stereo is set loud enough to drown out
ordinary conversation, this may well be a signal that it is also loud enough to
damage your hearing. Experts caution that two to three hours of exposure to 90
decibels can damage your ears. Earplugs or other hearing-protection devices are
recommended whenever you are in a noisy environment.
Parents do well to remember that children are
more susceptible to hearing damage than are adults. Keep in mind the potential
danger of noisy playthings. Why, a toy rattle can reach 110 decibels!
Our ears are delicate, small, and wonderful
mechanisms. With them we can hear all the varied and beautiful sounds of the
world around us. Surely, this precious gift of hearing deserves to be
protected.
Approximate Decibel
Level of Some Common Sounds
• Breathing—10 decibels
• Whispering—20 decibels
• Conversation—60 decibels
• Rush-hour traffic—80 decibels
• Food blender—90 decibels
• Passing train—100 decibels
• Chain saw—110 decibels
• Passing jet plane—120 decibels
• Shotgun blast—140 decibels
You May Be Losing
Your Hearing if You
• Increase the volume on the radio or TV but
others find it uncomfortably loud
• Continually ask others to repeat themselves
• Often frown, lean forward, and turn your
head in order to hear the one speaking to you
• Have difficulty hearing at public
gatherings or when there is noise in the background, such as at a social
gathering or in a busy store
• Often depend on others to tell you what was
said
Things That Can Go Wrong
Given the
outer ear's exposure to the elements and the middle ear's connection to the
nose via the Eustachian tube, more than a few things can affect the ear and
bring on hearing loss. Fortunately, most of these conditions can be treated
effectively if they're detected early by a doctor.
Some of
the more common ear problems include:
Noise-induced
hearing loss (NIHL).
This hearing loss is brought on by too much exposure to loud noise. Loud noises
can damage the hair cells in the cochlea. For kids in America, one of the main
culprits is portable music players. Video games, TVs, movie theaters, traffic,
power tools, and even some appliances can also be too noisy for most people. NIHL
also can be caused by a onetime exposure to a very loud sound, such as an
explosion or thunderclap. NIHL is almost 100% preventable if you protect your
ears.
Otitis
media. This
infection of the middle ear is the most common cause of hearing loss in children.
It can affect one or both ears and happens when pus and mucus build up behind
the eardrum if the Eustachian tube gets blocked by allergies or a cold or upper
respiratory infection. Otitis media, if not treated, can damage the eardrum,
causing hearing loss and an infection of the mastoid bone behind the ear.
Otitis
externa. Also
known as "swimmer's ear," this infection of the outer ear happens
when water and bacteria get trapped in the ear canal. The bacteria can multiply
in the warm, moist environment, leading to irritation and infection of the skin
lining the ear canal. This is called "swimmer's ear" because it's a
common problem for swimmers, but it can affect anyone who bathes or takes a
shower.
Tinnitus. A ringing, humming, buzzing,
roaring, or clicking in the ears is known as tinnitus. It happens as a result
of damage to nerve endings in the inner ear. In young people, the main cause of
tinnitus is exposure to loud noises. Medical treatments or hearing devices can
often help people who have tinnitus.
Impacted
earwax. Earwax,
also known as cerumen, traps dirt and dust before they reach the eardrum.
Usually, earwax dries and falls out of the ear or is washed away. But in some
people it can build up and plug the inside of the ear canal (known as
"impaction") and cause hearing loss. Fortunately, doctors and nurse
practitioners can usually treat this kind of hearing loss simply by washing
away the wax. Because earwax can get impacted, doctors recommend never using
cotton swabs in the ear canal because doing this can push wax deeper into the
ear canal and make it harder to get out.
Ruptured
eardrum. A
puncture or rupture of the tympanic membrane is known as a ruptured or
perforated eardrum. Ruptured eardrums are sometimes accompanied by pain,
discharge from the ear, and decreased hearing. Ruptured eardrums often heal on
their own, but sometimes people need surgery to repair the rupture. Things can
get serious if water gets into the middle ear. So if you have a ruptured
eardrum, your doctor will tell you how to protect your middle ear from water
and bacteria while it heals.
Cholesteatoma. This is a type of skin cyst that
affects the middle ear. Someone can be born with cholesteatoma, but usually
it's a complication of chronic otitis media. If the Eustachian tube isn't
working properly, it can cause negative pressure in the middle ear. This pulls
the eardrum into the middle ear, creating a cyst or pocket that can fill with
dead skin cells and other waste material and become infected. People who have
cholesteatoma need to get surgery to remove the cyst. If it's not treated, it's
possible for the infection to spread to the brain, causing more serious
problems like meningitis.
Meniere's
disease.
Meniere's disease causes problems with balance and hearing. It occurs when a
part of the semicircular canals called the endolymphatic sac becomes
swollen. This affects the movement of the fluid in the canal and sends an
incorrect signal to the brain regarding body position and balance. Episodes of
Meniere's disease, which can produce severe dizziness, can happen without
warning. Some people get them a lot, others as rarely as once a year. Doctors
don't know exactly what causes Meniere's disease, and it can't be cured. But
there are treatments and things people can do to help relieve symptoms.
Injuries,
burns, and frostbite. Exposed
to the elements as they are, your ears are subject to all manner of minor
injuries. Usually that's no big deal, but an injury to the outer ear or ear
canal can lead to bleeding and infection that may affect other parts of the
ear. A direct blow to the ear, such as from a car accident or sports injury,
may tear the eardrum, dislocate the ossicles, or damage the inner ear. Repeated
hits to the outer ear can cause bruising and blood clots that disrupt blood
flow to the cartilage of the pinna and damage its shape and structure. This
condition is called "cauliflower ear."
Piercing
problems. If you
decide to pierce your ears, go to reputable, trained practitioners in clean,
sanitary surroundings. Because piercing breaks the skin, there's always a risk
of infection. To protect against germs, use a cotton ball or swab to apply
rubbing alcohol or antibiotic ointment to the earlobe around each earring.
Earrings should be made of surgical-grade stainless steel or 18 or 24-karat
gold. Rotate the earrings at least twice a day to keep the holes open while
they heal. Pierced earlobes generally take about 6 to 8 weeks to heal. Pierced
ear cartilage takes 4 months to a year to heal completely.
Things to remember
- Once hearing is damaged, it often can’t be restored. Too loud for too long is wrong.
- Avoid exposure to noise when you can and wear earplugs in noisy environments, such as discos or motor racing events.
- Certain chemicals and drugs can damage your hearing if taken over a long period of time.
Can noise affect more than my hearing?
A ringing
in the ears, called tinnitus, commonly occurs after noise exposure, and often
becomes permanent. Some people react to loud noise with anxiety and
irritability, an increase in pulse rate and blood pressure, or an increase in
stomach acid. Very loud noise can reduce efficiency in performing difficult
tasks by diverting attention from the job.
References:
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