Marine Corps Base Quantico --
Since 1917, Marine Corps Base Quantico has been training
Marines, enlisted and officers, to be the tip of the spear in America’s
military leadership at home and abroad. Much of this training involves
live-fire exercises, including small-arms and crew-served weapons fire, as well
as mortars and precision, air-delivered munitions.
Quantico is home to 34 live-fire ranges that cover more than
56,000 acres in Prince William, Stafford and Fauquier counties.
For nearly a century, the land where the Chopawamsic and
Quantico creeks converge into the Potomac River, the Marine Corps has prepared
leaders to fight the nation’s battles. It is the only installation where Marine
Corps officers are created and trained.
As some may have experienced, Quantico’s mission sometimes
makes noise.
“For Marines to win the battle, the leaders must experience
these weapons and munitions firsthand,” said Maj. Andrew Bormann, public
affairs officer for Quantico. “That’s why we run training exercises in as
controlled an environment as we possibly can.”
Last year, Quantico undertook a comprehensive study of range
data, atmospheric conditions and comments made to base personnel by residents
from the surrounding areas.
Analyzing five years of data (2008-2012), the base Business
Performance Office, with support from the Range Management Branch, the PAO and
the Marine Corps Air Facility Meteorological Section, determined that there
were more than 920 days at MCBQ when Marines or other Federal, state or local
agency officials were conducting live-fire training with high-caliber weapons
or artillery or were engaged in demolitions training. At MCBQ, live-fire
training was conducted at least every other day during the five years studied.
The study, not surprisingly, concluded that artillery and
close-air-support training accounted for most of the noise reports, especially
in winter. The geographic location of where the reports came from varied widely
over the surrounding area.
In 2013, there were 225 comments from residents in the
surrounding counties who notified base officials that they were able to hear
noise they perceived was coming from the base. Of those comments:
• 115 were positive comments
• 78 were neutral
• 32 were negative.
While those 2013 numbers were not correlated with
atmospheric data, weather conditions do impact the way sounds travel. Many
academic and engineering studies corroborate how weather related to sound
travel.
According to a report published by Simon Frasier University
in British Columbia, Canada, “There are several important factors which affect
the propagation of sound: geometric spreading, atmospheric effects and surface
effects. … High frequencies are absorbed more than low. The amount of
absorption depends on the temperature and humidity of the atmosphere.”
Additionally, according to engineers at Acoustics by Design,
one of the nation’s leading independent acoustical consulting firms, “wind
alters sound propagation by the mechanism of refraction; that is, wind bends
sound waves. Wind nearer to the ground moves more slowly than wind at higher
altitudes, due to surface characteristics such as hills, trees and man-made
structures that interfere with the wind. This wind gradient, with faster wind
at higher elevation and slower wind at lower elevation causes sound waves to
bend downward when they are traveling to a location downwind of the source and
to bend upward when traveling toward a location upwind of the source. Waves
bending downward means that a listener standing downwind of the source will
hear louder noise levels than the listener standing upwind of the source. This
phenomenon can significantly impact sound propagation over long distances and
when wind speeds are high.
“Another factor that can impact sound propagation over long
distances is temperature gradients in the atmosphere,” as reported by Acoustics
by Design’s Oct. 2008 report. “On a typical sunny afternoon, air is warmest
near the ground and temperature decreases at higher altitudes. This temperature
gradient causes sound waves to refract upward, away from the ground and results
in lower noise levels being heard at the listener’s position. In the evening,
this temperature gradient will reverse, resulting in cooler temperatures near
the ground. This condition, often referred to is a temperature inversion will
cause sound to bend downward toward the ground and results in louder noise
levels at the listener position. Like wind gradients, temperature gradients can
influence sound propagation over long distances and further complicate
measurements.”
Or, as more simply described on the website,
strangesounds.org, “think about a seashell. It captures the ambient noise from
the environment. The sound resonates inside the shell and produces a wavelike
noise; no matter how far away one is from the ocean. The walls of the seashell
capture and direct sound to our ears.
“It is almost the same when the weather conditions are
right. The sounds and booms are captured much like the seashell. Indeed, when
the air is calm and still, most likely in the morning, the cool and dense air
sinks toward the Earth’s surface and produces a temperature inversion layer.
This layer of cool and dense air produces a sound channel much like the walls
of the seashell.”
The sounds of Marines training sometimes reaches outside the
confines of the base. Some call it bothersome, some call it “the sound of
Freedom.” Either way, it’s a byproduct of training to meet the mission of the
United States Marine Corps.
For more information and current noise advisory please visit
www.quantico.marines.mil/Advisories.aspx