Hearing loss caused by noise can occur in people of
any age. It may develop suddenly or gradually, depending on the source and
intensity of the noise. Noise can affect hearing in several ways.
- Acoustic trauma occurs
when a sudden, extremely loud sound, such as an explosion, a gunshot, or a
firecracker close to the ear, damages any of the structures in the ear and
produces an immediate, severe, and permanent hearing loss. This type of injury
often requires immediate medical attention.
- Temporary threshold shift occurs when loud sounds (such as
from a rock concert) cause a temporary ringing and hearing loss. Sounds may
also seem muffled. These effects usually don't last more than a few hours,
although they may sometimes last several days or weeks. Repeated exposure to
sounds that cause temporary threshold shifts can gradually lead to permanent
threshold shifts, commonly referred to as noise-induced hearing loss.
- Noise-induced hearing loss is the result of
repeated, frequent exposure to loud or moderately loud sounds over a long
period of time (often years). Though permanent, this kind of hearing loss is
almost entirely preventable.
How loud a noise is and how long you are around it determine whether
a noise is harmful. On-the-job (occupational) noise is one of the most common
sources of harmful noise, largely because you are around it all day for years.
For instance, if you work in construction, in a factory, or are in the
military, you may be around harmful noise for several hours each day.
The sounds of recreation and daily activities over many years can
also damage the ear and cause hearing loss. These include:
- High-volume music.
- The noise of power
tools, such as chainsaws or electric drills.
- The noise from lawn
mowers, household appliances (such as blenders and vacuum cleaners), and
vehicles (such as snowmobiles and motorcycles).
You can reduce harmful noise levels and prevent noise-induced damage
to your hearing by avoiding noisy situations whenever you can. When you can't
avoid noisy situations, wear hearing protectors such as earplugs or
earmuffs.
Noise-induced hearing loss is usually permanent and cannot be
reversed. Hearing aids, which make sounds louder, are often helpful for this
type of hearing loss.
How does noise-induced hearing loss develop?
To be heard, sound energy has to be strong enough to bend tiny hair
cells in the cochlea, a part of the inner
ear 
. The force of loud noise can damage these hair
cells. A small amount of damage may have no effect on hearing. With repeated
exposure to noise, however, more of the hair cells are damaged, resulting in
hearing loss.
Noise-induced hearing loss usually affects both ears. However, one
ear may be affected more than the other if you have had repeated, long-term
exposure to a loud sound that is always coming from the same direction, such as
gunfire that is always near the same ear.
