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Map of sound complaints called into Marine Corps Base Quantico.

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What's that noise: understanding training noise at Quantico

8 Dec 2014 | David M. White 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   


Marine Corps Base Quantico