Sounds clear, let's have a fish fry!

August 21, 2022 10:37 AM

Outdoor Sound Propagation in the U.S. Civil War. "In each of these seven battles listed above, the inability of commanders to hear and interpret the sounds of battle was directly responsible for the outcome. One might even go so far as to say the acoustical shadows determined the course of the entire war."
posted by kaibutsu (21 comments total)

It's understandable that a professor of physics should want to stress the role of acoustics in determining the outcome of battles. But this is basically a case of the blind men and the elephant, i.e. the specialist only sees their own little piece of the puzzle.

The bigger issue is that battlefield communications were poor to non-existent, and once the fighting had started it was almost impossible to know what was going on:

The cloud of unknowing which descended on a First World War battlefield at zero hour was accepted as one of its hazards by contemporary generals. Since the middle of the nineteenth century, the width of battlefields had been extending so rapidly that no general could hope to be present, as Wellington had made himself, at each successive point of crisis; since the end of the century the range and volume of small-arms fire had been increasing to such an extent that no general could hope to survey, as Wellington had done, the line of battle from the front rank. The main work of the general, it had been accepted, had now to be done in his office, before the battle began. (John Keegan, The Face of Battle)

The sounds of battle (the 'confused alarms of struggle and flight', as Matthew Arnold calls them in Dover Beach) are clearly a part of this. But to say that 'the acoustical shadows determined the course of the entire war' is to mistake the part for the whole.
posted by verstegan at 11:38 AM on August 21, 2022 [7 favorites]

The hyperbole may be a bit much, but this is still a cool read if your internal Venn diagram of “US Civil War” and “Tech Nerd” has any overlap at all.
posted by Thorzdad at 11:43 AM on August 21, 2022 [2 favorites]

The bigger issue is that battlefield communications were poor to non-existent...

Which is why they relied on things like being able to hear the start of an artillery barrage to coordinate.
posted by ChurchHatesTucker at 11:47 AM on August 21, 2022 [3 favorites]

Local favorite Bret Deveraux just published a whole series on an adjacent topic, the inability of generals in pre-modern (really pre-radio) armies to know much of anything at all about the progress of their campaigns:

The upshot of all of this is that at each stage of the fight – the march to the battle, the night before, the forming of the battle array and then the battle itself – the information environment the general is forced to operate in is heavily constrained. … Instead the general’s role was if anything more complex and difficult: he had to manage an uncertain information environment, attempting to ascertain how his enemy intended to fight from incomplete and occasionally outright false reports and his own knowledge of how the enemy tended to fight battles.

posted by migurski at 11:47 AM on August 21, 2022 [6 favorites]

Cool! I heard an NPR piece on the topic years ago-- one of their few pieces that *wasn't* about a book. Maybe it's by the same person.
posted by Nancy Lebovitz at 12:22 PM on August 21, 2022

Interesting. This phenomenon is mentioned several times in Shelby Foote's history of the civil war, but no scientific explanation was ever given (at least not that I recall. It's been over ten years since I read it.)

Lack of communication is another good reason to try to take the high ground in battle, if possible. At least you can hopefully see what the hell is going on out there.
posted by freakazoid at 12:57 PM on August 21, 2022 [2 favorites]

Fascinating. It adjusts the received idea of a commander being too far from the field to know what's going on a bit. For example:


Johnston, at his headquarters near Fair Oaks a few miles from the front lines, did not hear the battle and could not be convinced by others that a fight was raging....

The battle, silent to Johnston two miles from the front, was heard clearly by citizens of Richmond ten miles to the west and to Federals as far to the east. The probable cause was a temperature inversion bending the sound back to the ground. On the night before the battle, a violent thunderstorm (many soldiers said it was the worst they had ever seen) raged over the area. The day of the battle dawned with widespread, low cloud cover-ideal conditions for a low- atmosphere temperature inversion.
posted by doctornemo at 2:08 PM on August 21, 2022 [3 favorites]

These days Civil War stuff has an immediacy for me that I never anticipated.

Sometimes upwardly refracted waves hit a warmer layer higher up and are refracted back down, creating rings of audibility, as in the battle of Gettysburg as well as in the European examples previously described.

I’ve always assumed that sound waves would partially reflect from a boundary layer in the atmosphere somewhat like light waves would — I mean, I don’t expect Snell's law and an angle of total internal reflection, but counterparts at least.

But perhaps he's using 'refraction' in some larger sense that includes reflection.

The anecdotes at the beginning of the article are amazing:

Unusual acoustics due to atmospheric conditions or to terrain are sometimes given the catch-all name "acoustic shadows." The first recorded incidence of the phenomenon occurred during the Four-Day Battle in 1666. The naval battle was fought between the coasts of England and Holland, and sounds of the battle were heard clearly at many points throughout England but not at intervening points. Passengers on a yacht positioned between the battle and England heard nothing. A number of other examples have been recorded since that time. Guns fired at the funeral of Queen Victoria in London in 1901 were heard in Scotland, but not across a wide region in between. The German bombardment of Antwerp in World War I was heard clearly for a 30-mile radius, then beyond 60 miles from the Belgian city, but not in between.

posted by jamjam at 2:10 PM on August 21, 2022 [2 favorites]

I have this post to thank for learning about the shad bake (and acoustic shadow) that cost the Confederacy its last useful defensive line.
posted by Earthtopus at 5:21 PM on August 21, 2022

To be fair, shad sounds pretty tasty. It's been described as "the fish that fed the nation's founders" and its "considered flavorful enough to not require sauces, herbs, or spices."
posted by kirkaracha at 7:07 PM on August 21, 2022

Count me among the skeptics who wonder if, given the unreliability of the mere sounds of battle, the forces in question wouldn't rely more on visual signals--such as, say, the semaphore flags that are still the insignia of the US Army's Signal Corps. I also wonder about some of his information, such as that Richard Ewell simply didn't hear the artillery barrage that was supposed to signal him to attack at Gettysburg. Here's how Wikipedia describes it:

Ewell had several possible reasons for not attacking. The orders from Lee contained an innate contradiction. He was "to carry the hill occupied by the enemy, if he found it practicable, but to avoid a general engagement until the arrival of the other divisions of the army." Lee also refused to provide assistance that Ewell requested from the corps of A. P. Hill. Ewell's men were fatigued from their lengthy marching and strenuous battle in the hot July afternoon and it would be difficult to reassemble them into battle formation and assault the hill through the narrow corridors afforded by the streets of Gettysburg. The fresh division under Maj. Gen. Edward "Allegheny" Johnson was just arriving, but Ewell also received intelligence that heavy Union reinforcements were arriving on the York Pike from the east, potentially threatening his flank. Ewell's normally aggressive subordinate, Maj. Gen. Jubal A. Early, concurred with his decision.

I find it unlikely that it took until 1999, over 130 years after the battle itself--one of the most heavily-analyzed battles in American history--for someone to suggest that Ewell failed to take the hill, and therefore maybe not just losing the battle but the war itself, because he simply failed to hear the cannon.
posted by Halloween Jack at 7:15 PM on August 21, 2022

Count me among the skeptics who wonder if, given the unreliability of the mere sounds of battle, the forces in question wouldn't rely more on visual signals--such as, say, the semaphore flags that are still the insignia of the US Army's Signal Corps.

Not until a few years afterwards.

Flag semaphore originated in 1866 as a handheld version of the optical telegraph system of Home Riggs Popham used on land, and its later improvement by Charles Pasley.

Flag Semaphore
posted by ChurchHatesTucker at 7:26 PM on August 21, 2022

Count me among the skeptics who wonder if, given the unreliability of the mere sounds of battle, the forces in question wouldn't rely more on visual signals

"Everything is very simple in war, but the simplest thing is difficult." Clauswitz
posted by justsomebodythatyouusedtoknow at 7:59 PM on August 21, 2022 [1 favorite]

This is reminiscent of the "quiet zone" around Mt St Helens, up to several hundred kilometres across, within which the 1980 blast was not heard. Meanwhile, up to 700 km away in Canada and California the blast was clearly heard in many places, including being loud enough to startle my mom on southern Vancouver Island.
posted by Rumple at 10:36 PM on August 21, 2022 [2 favorites]

That’s fascinating Rumple!

I’ve done some desultory searches for evidence that anyone has ever heard a nuclear, volcanic, or meteoric (such as Chelyabinsk and Tunguska) blast at of near the antipodal point and come up with nothing.

I was in Seattle when Mt St Helens blew and heard nothing, and I don’t recall hearing that any other Seattleites did either.
posted by jamjam at 12:05 AM on August 22, 2022 [2 favorites]

Flag semaphore originated in 1866 as a handheld version of the optical telegraph system of Home Riggs Popham used on land, and its later improvement by Charles Pasley.

Yes, but, the US Army Signal Corps insignia doesn't show semaphore flags, the are wigwag flags. Wigwag encoded a message based on the movement, instead of position, of flags or torches. Wigwag was developed by the US Army in the 1850's and was widely used by both Union and Confederate armies starting with the First Battle of Manassas.
posted by peeedro at 8:32 AM on August 23, 2022 [3 favorites]

Wigwag was developed by the US Army in the 1850's and was widely used by both Union and Confederate armies

Oh, interesting. I had no idea there was a signal station on Little Round Top!
posted by ChurchHatesTucker at 10:53 AM on August 23, 2022 [1 favorite]

such as that Richard Ewell simply didn't hear the artillery barrage that was supposed to signal him to attack at Gettysburg.

You're talking about a different moment at Gettysburg. The hesitancy by Ewell that you're pointing to was on July 1 (hence the reference to moving through the streets of Gettysburg) when he had a chance to attack Cemetery Hill. The linked article is talking about July 2 when Ewell was supposed to attack Culp's Hill.

In general, though, the article's descriptions of the battles are a bit skewed. Ewell didn't attack at Gettysburg because he thought Lee only wanted a demonstration, not because he didn't hear the sound of cannon fire. He actually started firing on Culp's Hill at about 4 pm on July 2, well before the crisis on Little Round Top.

At Five Forks, it wouldn't have mattered if the Confederate commanders had heard the gun fire -- the battle was over much too quickly for them to react even if they had heard it.

The other part of this is that experienced generals in 19th century warfare were well aware of the vagaries of sound, so none of this would have been particularly new to them.
posted by Galvanic at 10:54 AM on August 23, 2022

jamjam - I have this pretty strong memory that soon after the Mt St Helen eruption a local scientist was trying to map the acoustic patterns across the region. In an early example of citizen science(?) he was having people send in postcards of if they heard it or not and where. In my earlier link there are only a couple of dozen data points so I don't think this was the same study. Instead, this person's result was a series of huge irregular rings of audibility and quiet, due partly to how infrasound interacts with local topography in ways that make it audible.

I may be getting something wrong here but I believe there were hundreds or even thousands of postcard replies, however even though I am not bad at research I can't find any reference to this study. Maybe it was a newspaper thing and not science per se.

Anyway, off topic, an interesting though not obviously scholarly video includes a recording of the recent Tonga eruption in Anchorage, Alaska (time stamped) which is not how I imagined the sound would be, at all. It suggests a mechanism, noting that the explosion was not heard in Japan or California or Hawaii despite similar amplitudes of atmospheric disturbance. Indeed, a Hawaiian researcher has created an app to detect infrasound from large explosions or eruptions - I haven't tried this myself!
posted by Rumple at 11:17 AM on August 23, 2022 [1 favorite]

In general, though, the article's descriptions of the battles are a bit skewed. Ewell didn't attack at Gettysburg because he thought Lee only wanted a demonstration, not because he didn't hear the sound of cannon fire. He actually started firing on Culp's Hill at about 4 pm on July 2, well before the crisis on Little Round Top.

I noticed that as well.

There was no delay on Ewell's behalf that allowed the Union army to protect their far left flank. Credit goes to Union Brigadier General Gouverneur K. Warren, who was acting on orders from Meade to secure the unprotected flank. From the signal station on Little Round Top, he was able to see glinting of bayonets behind tree cover giving away the Confederate advance. He ordered Union troops to fill in the line just in time. Colonel Vincent's brigade arrived before the Confederate artillery assault began. Longstreet's artillery bombardment started at 4pm, the same with Ewell's. That's quite a coincidence for two forces unable to coordinate because the sound of cannon fire was blocked by terrain and weather.

The other coincidence is that his theory happens to focus on the two Lost Cause scapegoats of Gettysburg: Ewell and Longstreet. I'm kinda curious which history books this guy has been reading because it feels like some hand-wavey scientific proof that ol' Bobby Lee did nothing wrong.
posted by peeedro at 6:12 PM on August 23, 2022 [2 favorites]

The other coincidence is that his theory happens to focus on the two Lost Cause scapegoats of Gettysburg: Ewell and Longstreet. I'm kinda curious which history books this guy has been reading because it feels like some hand-wavey scientific proof that ol' Bobby Lee did nothing wrong.
posted

Great point -- I hadn't noticed that.
posted by Galvanic at 7:41 AM on August 24, 2022