Hearing loss is the major consequence of the loud noises found in a
military environment. Loudness is measured by a unit called the
decibel. To get an idea of the intensity of a decibel, a quiet
library might be measured at about 40 decibels; a handsa equals 85
decibels; a power saw, 110 decibels; a jackhammer, 130; artillery fire
(at 500 feet), 150 decibels; and a rifle (close range), 165.
For every 10 decibel increase, there is a 10-fold increase in noise
energy. That means the intensity of a 50 decibel sound is ten times
that of a 40 decibel sound, and a 60 decibel sound is 100 times a 40
decibel sound. The the intensity of a rifle blast is many million
times more intense than the sound in a library.
The US Occupational Safety and Health Administration (OSHA), limits
the permissible exposure of workers to loud noises. For example, a
worker may be exposed to a 90 decibels or less of noise for 8 hours a
day, but to a sound of 115 decibels for only 15 minutes.
Hearing loss is one of the most common causes of workers' compensation
claims in the military. The highest rates of hearing loss are in the
combat-related occupations, for example infantry or artillery.
Hearing protectors lower the number of decibels reaching the hearing
apparatus inside the ear. This is accomplished by earplugs and
earmuffs or a combination of the two.
Earplugs fit inside the ear canal. They must seal the canal to be
effective. Earmuffs cover and seal off the entire outer ear. Plugs
and muffs can lower noise levels by 15 to 30 decibels. If both are
worn, reduction is an additional 10 to 15 decibels. In a combat
situation, these would be worn under a sound-reducing helmet to
further lower the intensity of noise reaching the ear.
Below is a summary of types of hearing protective devices on the
Expandable foam plugs: these are rolled to fit into the ear canal,
then expand to make a tight fit. They are used only once and
Pre-molded, reusable plugs: also fit into the ear canal and are made
from silicone, plastic or rubber. They are available as
?one-size-fits-most,? or are made in small, medium or large. Note that
a person might need a different size for each ear.
Canal caps: these are earplugs on a flexible plastic or metal band.
The earplug tips may be formable or pre-molded . The headbands can be
worn over the head, behind the neck or under the chin. Newer models
have jointed bands increasing the ability to properly seal the
earplug. When not in use they can be hung around the neck.
Earmuffs: these come in many models and materials. They help block out
noise by completely covering the outer ear. Muffs can have small ear
cups or large ones to hold extra materials for use in extreme noise.
Some muffs also include electronic components to help users
communicate or to block impulsive noises. Muffs are less effective
over beards or sideburns because the hair prevents a good seal.
So called "electronic hearing protectors" merely allow one way
communication into the ear protector. They have not proven more
effective than non-electronic protectors.
At present the most effective hearing protection is a combination of
earplugs and earmuffs. The "highest tech" effective protection is
found in the materials used to manufacture earmuffs.
It seems that "finger-in-ear" hasn't made the government's rating list
All the best,
League for the Hard of Hearing
American Academy of Otolaryngology
OSHA Occupation noise exposure, Table 16-G
CDC National Institute of Occupational Safety and Health Hearing Loss