T H E S O U N D O F
The idea of silencing a gunshot has been around for quite some time.
As early as 1909, the first commercially successful silencer was patented
by Hiram Percy Maxim. As more and more countries are allowing the
civilian use of silencers, these devices have never been more popular.
So it appears silencers have a lot more going for them than just
protecting shooters’ hearing.
GUNSHOT SOUND ANATOMY
When a gun is fi red, sound is produced in three
Th e fi rst, most important factor is muzzle blast
generated by high-temperature, high-pressure gases
escaping and expanding from the muzzle after the
bullet exits the barrel. All this is directly proportional
to the amount of propellant combusted but can be
managed by the use of a silencer. Th e bigger the case
capacity and the more propellant is used, the louder
the muzzle blast and consequently a more effi cient or
larger silencer system is required.
Th e second factor is sonic boom, a sound associated
with high-frequency shockwaves created by an object
fl ying through the air and exceeding the speed of sound
(343.2 metres per second). Th is factor can be managed,
if one so desires, by using subsonic ammunition
that does not exceed the speed of sound. Subsonic
ammunition often uses heavier bullets to retain as
much energy as possible at lower velocities.
Th e third sound-producing factor is mechanical
noise. Th is is generated by internal moving parts of the
fi rearm action related to the fi ring of a gun. Th is part
can be managed as well but mostly is beyond the ability
of the operator or manufacturer to really eliminate.
Hearing loss can be caused by a one-time exposure to
an intense “impulse” sound, such as a gunshot, or by
continuous exposure to loud sounds over an extended
period of time, such as noise generated at a building
Sound is measured in units called decibels. Sounds
of less than 75 decibels, such as a normal conversation
at 60 decibels, are unlikely to cause hearing loss,
even after long exposure. However, long or repeated
exposure to sounds at or above 85 decibels, such as a
lawnmower at 95 decibels, ambulance sirens at 120
decibels or a gunshot at 150 decibels, can eff ectively
cause hearing loss. Th e louder the sound, the shorter
the amount of time it takes for hearing loss to occur.
HOW HEARING LOSS OCCURS
To understand how loud noises, such as gunshots, can
damage our hearing, we need to understand how we
hear. Our hearing depends on a series of events that
changes sound waves in the air into electrical signals.
Our auditory nerve then carries these signals to the
brain through a complex series of steps. First, sound
waves enter the outer ear and travel through a narrow
passageway called the ear canal, which leads to the