[HN Gopher] Outdoor Sound Propagation in the U.S. Civil War
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Outdoor Sound Propagation in the U.S. Civil War
Author : sdenton4
Score : 72 points
Date : 2022-08-21 17:53 UTC (5 hours ago)
(HTM) web link (wesclark.com)
(TXT) w3m dump (wesclark.com)
| balentio wrote:
| This is a not widely documented Civil War phenomenon, but happens
| probably quite often without people knowing it since by
| definition, it is the ABSENCE of sound that has to be noticed.
| jchanimal wrote:
| Similar historic outcome. I was in the room for Howard's Dean
| "scream". which basically ended his campaign. As far as I can
| tell the cause was not enough attention paid to the microphone
| sound reinforcement. He had to push too hard to be heard in the
| raucous room.
| arminiusreturns wrote:
| I'd like to find the history of declaring that scream ended his
| campaign. Since you were there, did anyone in the crowd react
| in that manner afterwards, or was it really just an excuse the
| media used to lambast him artificially (which is what it felt
| like to me)?
| chrisseaton wrote:
| Did it sound weird in the room, or was it only on the
| recording?
| [deleted]
| Domobran7 wrote:
| That is really interesting. Honestly, I had never even thought
| about it until now, but now it reminded me of how Titanic may
| have sunk due to fatamorgana.
|
| Weather really does play major role in human history, even when
| you don't see or expect it.
| balentio wrote:
| prenoob wrote:
| OT but related: if the subject matter is of interest to you you
| may enjoy this book ->
| https://www.google.com/books/edition/Battlefield_Acoustics/O...
| hirundo wrote:
| If your network is good enough to gather a microphone's data from
| each soldier/drone on the battlefield, you could centrally
| assemble a very accurate location and type on any weapon fired
| and other ambient sound. That data could be used to evaluate
| risks and return fire accurately within milliseconds. It could
| give a general a lack of fog-of-war only available before in
| simulations.
| bragr wrote:
| I'm not sure this is true given the inaccuracy of shotspotter
| h2odragon wrote:
| I think shotspotter's problems are more political than
| technical.
|
| Not to say they don't have technical challenges too: better
| _sensors_ than the human ear turn out to be fairly easy, but
| interpreting that data is still hard. Brains are complicated,
| "hearing" is a process contributed to by nearly every layer
| of meat that reacts to sound. The human ability to notice a
| new noise in the cacophony of everyday life is really an
| amazing trick if you think about it.
| sdenton4 wrote:
| I know a non-shotspotter effort to identify gunshot sound
| in a very different context which also is having a very
| hard time; there is a real unsolved technical problem here.
| And it makes me think that ID'ing gun model from audio -
| which will be harder than simply identifying the existence
| of gunfire - is going to be very difficult.
| livueta wrote:
| Yes, but with caveats. Disclaimer: just a hobbyist, not my
| professional area, corrections appreciated
|
| - oldschool radio direction-finding with a couple of
| directional antennas that are manually positioned and rotated
| (i.e. based on signal attenuation) doesn't really work for
| point-in-time things like a single brief signal unless you have
| massive arrays of well-positioned receivers, which is fine if
| you're building an HFDF installation but not fine if you're a
| squad on the move
|
| - multilateration on the basis of signal attenuation, analogous
| to that sort of oldschool RDF, is possible but IME doesn't
| perform very well; same problem where you often need a lot of
| well-positioned points to shrink the possibility envelope down
| to something useful
|
| - multilateration on the basis of time of arrival, analogous to
| more modern pseudo-doppler / correlative interferometry RDF
| techniques, can perform a lot better but requires a very high
| quality shared time source - if the model is analyzing info
| from an array of observers, this can be a problem on typical
| battlefield network designs that prioritize availability over
| performance - but this approach also enables single site setups
| where a local time source and a handful of receivers can read a
| bearing without actually needing to network at all, though this
| involves a lot of math
| wbl wrote:
| GPS solves the sync issue to the order of nanoseconds. You
| can also have local TOA determine angles that get passed up
| to triangulate. The US Army deployed some of these techniques
| in antisniper work in Iraq.
| livueta wrote:
| That's a good point, and required time precision seems like
| it should be proportional to the velocity of the signal
| being investigated. I had some bad experiences trying to
| use gps time for RDF, but that might not apply here.
|
| From https://www.usenix.org/legacy/events/mobisys07/full_pa
| pers/p...
|
| > Our time synchronization approach yields errors signif-
| icantly less than 100 microseconds. As the sound travels
| about 3 cm in that time, time synchronization errors have a
| negligible effect on the system.
|
| Sounds like it?
|
| The anti-sniper systems I knew about already (Boomerang)
| are that single-site setup where time sync isn't a problem.
| The "Individual Gunshot Detector" sounds more like what
| you're describing.
|
| > The Individual Gunshot Detector (IGD) by Qinetiq consists
| of a shoulder-mounted unit with four acoustic sensors and a
| chest display that attaches to body armor.
|
| Still looking for more detail, but that sounds like a local
| ToA > pass up angles for triangulation type deal.
| galangalalgol wrote:
| I read an ieee journal article over a decade ago claiming
| success with helmet mounted sensors. The system used the time
| of the sonic crack and the muzzle report as observed from
| each helmet. Its like GPS, if you have 5 or more observers
| you can solve for the time reference as well. Actually, it
| might be less since they had multiple observations from each
| helmet. It supposedly could then highlight the location of
| the shot using AR. It then went on to say they could tell
| what the firearm was from the muzzle report. Can't find the
| article now. Doesn't seem that outlandish, but as you say,
| accuracy would be the real question. The speed of sound can
| vary so much based on weather.
| livueta wrote:
| Maybe this? https://www.usenix.org/legacy/events/mobisys07/
| full_papers/p...
|
| > It then went on to say they could tell what the firearm
| was from the muzzle report.
|
| > over 95% caliber estimation accuracy for all shots, and
| close to 100% weapon estimation accuracy for 4 out of 6
| guns tested.
|
| That's pretty cool. Gotta read the whole thing now.
|
| e: kinda relevant to the other subthread about time sync:
|
| > Correlating ToA measurements requires a common time base
| and precise time synchronization in the sensor network. The
| Routing Integrated Time Synchronization (RITS) [15]
| protocol relies on very accurate MAC-layer time-stamping to
| embed the cumulative delay that a data message accrued
| since the time of the detection in the message itself. That
| is, at every node it measures the time the message spent
| there and adds this to the number in the time delay slot of
| the message, right before it leaves the current node. Every
| receiving node can subtract the delay from its current time
| to obtain the detection time in its local time reference.
| The service provides very accurate time conversion (few ms
| per hop error), which is more than adequate for this
| application. Note, that the motes also need to convert the
| sensorboard time stamps to mote time as it is described
| earlier.
| MichaelCollins wrote:
| > _within milliseconds._
|
| I think you're overestimating the speed of sound a bit. You'd
| need nearly 5 seconds to hear artillery fire a mile away.
| polishdude20 wrote:
| "Guns fired at the funeral of Queen Victoria in London in 1901
| were heard in Scotland"
|
| Wait how is this possible?
| MichaelCollins wrote:
| Probably the atmospheric version of SOFAR; thermal layers in
| the atmosphere acting as a wave guide for very low frequency
| sound waves. In the ocean, the sound of explosions can travel
| thousands of miles in the SOFAR channel.
|
| https://en.wikipedia.org/wiki/SOFAR_channel
| bee_rider wrote:
| It seems a bit odd, huh?
|
| I found on google:
|
| https://www.latimes.com/archives/la-xpm-1999-jun-24-me-49796...
|
| Interestingly similar phrase:
|
| > Guns fired at the funeral of Queen Victoria in London in 1901
| were heard in Scotland, but not across a wide region in
| between.
|
| > Guns fired at the funeral of Queen Victoria in London in 1901
| were heard in Scotland, but not in wide areas of northern
| England.
|
| Searching the exact phrase
|
| > "Guns fired at the funeral of Queen Victoria in London in
| 1901 were heard in Scotland"
|
| Turned up a couple sites, one from the national academies press
|
| https://nap.nationalacademies.org/read/25226/chapter/3
|
| but it appears in a "background" section of a work on highway
| engineering, not cited.
|
| The other sites seemed like maybe sketchy textbook sharing
| sites, so I didn't check them out.
|
| Seems like maybe a popular bit of questionable trivia?
| schmendreck wrote:
| analog31 wrote:
| Less background noise, and better hearing, may have been
| factors.
| stevenwoo wrote:
| Weather inversion where the sound the travels slightly faster
| and farther in different temperature air medium plus reflection
| of waves that would normally dissipate to upper atmosphere if I
| read this correctly. http://spectrums.com/sound-and-the-
| weather/
| [deleted]
| duskwuff wrote:
| In this context, "guns" probably means cannon, not small arms
| like rifles or pistols.
| bragr wrote:
| Even still, cannon fire from 250+ miles (at least, that's
| just to the border) seems improbable
| R0b0t1 wrote:
| Seems plausible base on my experiences outdoors, but it
| heavily depends on ambient conditions. Over such large
| distances I think the unlikely part is you do that trick
| twice, but even that is plausible merely by looking at
| seasonal changes.
| vidanay wrote:
| And there's my weekly reminder that the British Isles are
| SMALL.
| galangalalgol wrote:
| No kidding! I was on the interstate this last week and a
| sign showed more than twice that distance just to the
| next major city in the state. (along that highway, there
| were closer ones in other directions)
| pessimizer wrote:
| There's a saying that goes something like "Americans
| think 100 years is a long time, and Europeans think 100
| miles is a long way."
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(page generated 2022-08-21 23:00 UTC)