Sciencemadness Discussion Board

Sound of low/medium/high VoD explosives

Rocinante - 16-7-2019 at 07:39

Do you experience notable difference in the sound of low VoD explosives (flash powder), medium VoD ones (3 - 4 km/s) and high VoD ones (6 km/s +)?

If so, what is the exact mechanism behind it? The first, fast expansion around the charge doesn't seem to be that different, i.e. a 100 g spherical charge will detonate in a few microseconds in each case and blast sounds are in the 100 - 1000 Hz range, i.e. wave lenght of tens of cm.

wessonsmith - 16-7-2019 at 09:56

Quote: Originally posted by Rocinante  
Do you experience notable difference in the sound of low VoD explosives (flash powder), medium VoD ones (3 - 4 km/s) and high VoD ones (6 km/s +)?

If so, what is the exact mechanism behind it? The first, fast expansion around the charge doesn't seem to be that different, i.e. a 100 g spherical charge will detonate in a few microseconds in each case and blast sounds are in the 100 - 1000 Hz range, i.e. wave lenght of tens of cm.



I can tell you the faster my VOD the more of a sharp and crisp bang I experience. I have seen it visually in my detonations in a large body of water. The faster the VOD, the more opaque the white water shock wave is. Of course, I am using my iPhone in 1080p 240fps to actually see a snapshot of the shockwave.

[Edited on 16-7-2019 by wessonsmith]

XeonTheMGPony - 16-7-2019 at 16:18

the difference is caused by the shape of the pressure wave (Rise over time) which you can imagine changes with VOD

Low orders are more boomy, slower rate of rise on the leading edge of the pressure wave to peak amplitude.

Higher VOD is a sharper crack due to the short lead up to peak.

Distance will attenuate this to a degree but with a well tuned ear you can ruftimate the type. I'll dig through my library and see if I have any basic PDFs on the subject for you

simply RED - 16-7-2019 at 22:44

Due to the nature of the atmosphere - identical TNT equivalent detonating explosives will produce identical pressure vs time graphs. No matter the VoD, even a thermobaric explosive will produce almost identical graph to its TNT eq. as TNT, if no enclosing is presented...

Fantasma4500 - 16-7-2019 at 23:42

the report may come across as more robust from something releasing higher intensity of energy at the same time
perchlorate flash the slower burning particle size aluminium produces a sharper bang, where higher quality would be a deeper bang
move onto magnalium and its very deep, onto magnesium and its a slight bit deeper yet again
another thing to take notice of is oxygen balance negative formulations or compounds causes a slight Fuel-Air-Explosive effect which makes the bang very heavy

long back i managed to produce pitch black magnalium with coffee grinder and 150 mesh sieve (it was mostly +600 mesh of what came through)
this with simply potassium chlorate in a paper hemi was quite something, this basic composition in 50-50 by weight easily beat professional high quality fireworks compositions such as cobra 6

a hint from a mate was to add KNO3 to KClO4-MgAl
so i did. it was a new level
previously he had me try KClO4-Al-S, also quite something, very heavy compared to KClO4-Al
so off i went, i mixed KNO3-MgAl-S 44:44:12 by weight and KClO4-MgAl 50:50 by weight
then i mixed equal proportions of this
10 grammes of this mix in a nice paper tube absolutely obliterated the loudness of 26.5g of what they stuff in cobra 6, i believe the MgAl was just 325 mesh even

however with higher energy density, the echo that comes back at you will be more intense, again to really figure out this you must be well aware of oxygen balance in what you reference because that makes a major difference

i recall, one guy swapped the typical aluminium-binary mixture with magnalium, it wasnt OB negative even, but even at this point his 325 mesh MgAl produced a deeper bang than his 000 black aluminium
something funny about magnesium, both metals have basically same melting point, and if its both same oxygen balance, then i really dont have a clue why it would produce a deeper bang

MineMan - 17-7-2019 at 17:09

Magnesium’s boiling point is very low. Hence the ultimate FAE

Pyro_cat - 19-7-2019 at 19:04

I have to think back 30 years but a medium sized trash bag of oxy acetylene barely out performed in terms of "loudness" an old school pineapple that I assume was flash powder. Did them back to back. The oxy acetylene was definitely sharper in the way it shook things and was slightly different every time depending on the oxygen balance. From more of a boom to sharp crack, you can adjust it.

I did not learn that from the internet or anyone, there was no internet, I just assumed I should get a result cause of the way the torch popped and paying attention in chemistry class. That first small bag, pow, you must be kidding me THAT just happened ?!!! Be careful with this.

kratomiter - 7-8-2019 at 07:51

IIRC, if the shock wave is longer, the brain processes it as louder than a more prowerful but shorter shock wave.

Katie - 22-4-2020 at 16:49

Sound is nothing more than one’s body’s interpretation of a pressure wave, so there are more variables than just VOD. Distance from source, humidity, surroundings, orientation of your ears, level of wax in your ears, amount of explosive material, and conscious attention will all affect how you perceive the sound.

Personally, the closer I am, the sharper the sound. For example, holding a flame to a speck of lead azide on a butter knife has a loud sharp report, but if I’m setting off Ammonal or PLX from 100 yards away, I can’t tell the difference unless I’m using very different amounts. I have a virtually unlimited supply of PLX, lead azide, ANFO, ANNM, and Ammonal so next time I’m testing things out I’ll pay more attention to the sound and try some different conditions.

Sulaiman - 23-4-2020 at 02:19

I have little experience with 'energetics' but lightning sounds very different at different distances, so I'd expect similar for explosives