Thursday, April 7, 2011
Battlefield acoustical confusion
PBS has been running the old Civil War documentary by Ken Burns. On the fourth broadcast day there was a less than sixty second reference to an unusual phenomena...
What do the following sites have in common as made manifest by observational accounts: Gettysburg, Seven Pines, Iuka, Fort Donelson, Five Forks, Perryville and Chancellorsville...an acoustical phenomena.
An acoustic shadow is an area through which sound waves fail to propagate, due to topographical obstructions or disruption of the waves via phenomena such as wind currents. A gobo refers to a movable acoustic isolation panel and that makes an acoustic shadow. As one website refers to it, "an acoustic shadow is to sound what a mirage is to light". For example, at the Battle of Iuka, a northerly wind prevented General Ulysses S. Grant from hearing the sounds of battle and sending more troops. Many other instances of acoustic shadowing were prevalent during the American Civil War, including the Battles of Seven Pines, Gaines' Mill, Perryville and Five Forks. Indeed, this is addressed in the Ken Burns' documentary "The Civil War" (produced and aired on PBS, September 1990). Persons nearby would see the smoke and flashes of light but not the corresponding roar of battle, while those in more distant locations would hear the sounds distinctly.
Battle of Gaines’s Mill – More than 91,000 men were engaged in battle at Gaines’s Mill, Virginia on June 27, 1862. Confederate commanders and troops were less than two miles from the battlefield and could plainly see the smoke and flashes from the guns and artillery, but not a sound could be heard of the battle for two hours. Strangely, the battle sounds from the Battle of Gaines’s Mill were easily heard in Staunton, Virginia over one hundred miles away.
Five Forks – Fives Forks was fought from March 30 to April 1, 1865 and was part of the Appomattox Campaign. Confederate Generals George Pickett and Fitzhugh Lee were enjoying a shad bake with other generals north of Hatcher’s Run when the battle of Five Forks began a short distance away. Because of Acoustic Shadow, Pickett and Fitzhugh Lee were unaware a fight was under way. Pickett finally responded, but arrived late for the battle. Pickett and Fitzhugh Lee have been criticized by Civil War historians for not acting on "the dread immediacy of the crisis" at Five Forks.
The Battle of Gettysburg – The battle sounds from Gettysburg fought on July 1, 2, and 3, 1863 could be heard over one hundred miles away in Pittsburgh, but were not heard only ten miles from the battlefield.
"Thunderstorms and Cannons"