Sciencemadness Discussion Board

Why are some explosives louder than others?

Turner - 25-2-2014 at 18:03

I have detonated 20g of RDX before as well as 20g ETN. The ETN was much louder. The RDX makes a muffled thud noise, I would even say that this charge wasn't even as loud as the small aerial burst fireworks, ETN makes a Bang, although RDX provides just as much damage. Is this because ETN creates more heat upon detonation? According to this, what would be a relatively loud explosive? Maybe one that has aluminum powder in composition?

Never seen ANFO or ammonal explode, but I am sure ANFO wouldn't be nearly as loud as ammonal exploding. What about an over aluminized ammonal composition?

[Edited on 26-2-2014 by Turner]

numos - 25-2-2014 at 18:34

I'm just taking an educated guess but I think it has something to do with the explosion velocity, the faster the pressure wave travels the louder it's going to sound.

Edit:
Perhaps also the burn rate? Because RDX has a higher explosion velocity than ETN... Not sure if heat plays a role although heat would contribute to more expansion of gases.

I know what you mean though - but maybe it's not necessarily louder, just a different sound a sharp bang as opposed to a deep boom. A higher pitch tends to sound "louder"

[Edited on 2-26-2014 by numos]

DrAldehyde - 25-2-2014 at 20:50

Yes, I hope somebody jumps in with the basics here. I have been wondering the same thing. I haven't come up with a search string that gets the answer I am looking for. Like the report of a shotgun vs a high power rifle. Same question with explosives. Some give you a thundering rich euphoric booming sound vs. a sharp ringing painful sound. An explosive sound primer if someone doesn't mind.

goldenoranges - 25-2-2014 at 21:43

I think it does have to do with detonation velocity. Some things detonate super fast, make a very loud crack, other things like black powder in a CO2 Canister, haha, are still loud but a bit duller because it takes a bit longer to fully detonate, and the sound waves are still loud but last a bit longer.

Motherload - 25-2-2014 at 23:44

It doesn't have much to do with VOD as ETN and RDX are close enough.
I would suspect the actual frequency of sound being different. The decibel output is probably very similar but the human ear perceives them differently.
Kinda like the same lumen output lights ... Green seems brighter than red.

There might be a link between the by products generated upon detonation to the frequency of sound.
Like if more CO is produced as opposed to CO2 .... It sounds not as loud.

[Edited on 26-2-2014 by Motherload]

hyfalcon - 26-2-2014 at 02:06

I know a small amount of flash sounds louder than the same quantity of ANAl when used for reactive targets.

Praxichys - 26-2-2014 at 05:23

This thread has useful information:

Why is FP louder than fast detonation?

hissingnoise - 26-2-2014 at 07:40

Apropos very little in particular ─ I have a nervous cat who panics over loud noises and one night some time ago, what I assume was a small battery, exploded with a loud, sharp crack in my open fire and my cat ignored it completely . . .

I assume the sudden noise didn't register because of its very short duration!

As to the noise produced by detonation of HEs, it is the same for explosives of similar force, obviously ─ the perceived differences arise due to charge-positioning, wind velocity/direction, topology and various other factors . . .


VladimirLem - 26-2-2014 at 10:14

Quote: Originally posted by Turner  
I have detonated 20g of RDX before as well as 20g ETN. The ETN was much louder. The RDX makes a muffled thud noise, I would even say that this charge wasn't even as loud as the small aerial burst fireworks, ETN makes a Bang, although RDX provides just as much damage. Is this because ETN creates more heat upon detonation? According to this, what would be a relatively loud explosive? Maybe one that has aluminum powder in composition?

Never seen ANFO or ammonal explode, but I am sure ANFO wouldn't be nearly as loud as ammonal exploding. What about an over aluminized ammonal composition?

[Edited on 26-2-2014 by Turner]


i dont know, but ETN will detonate high order at even small quantities like 20g....RDX is less sensitive and may be just pratialy/low order detonated?
Released heat is of course a very important thing at this question....supressors at handguns cools down the expanding gasses, but its not like hollywood movies it gives still a realitive loud bang...

Anfo: AN, Motoroil (C)
Ammonal: AN, AL, Carbon containing stuff and TNT

yes...i guess, Ammonal will detonate louder^^, without the TNT, i doubt it will be much louder...but yes, ANFO is a "scilent" explosive compared to stuff likne ANNM, ETN and so on...

too many AL in an explosive will just fuck up the oxygen balance...i doubt that there will be a significant louder bang

MrHomeScientist - 26-2-2014 at 11:16

Lots of speculation here, to which I'll add (having no experience in energetics myself, but having a physics background): I tend to agree with the view that velocity has a lot to do with it. High velocity would produce a stronger pressure wave, which could sound louder than a longer duration "boom." Apparently to the human ear, the duration of a sound plays a role in "loudness" determination. The wikipedia article on Loudness (sort of surprising that that is a real thing) has a great section discussing this: http://en.wikipedia.org/wiki/Loudness#Explanation



But what would be really valuable is to see some actual data. First, measure the sound output of equal amounts of your substances under identical conditions (i.e. confinement) and see if one is actually louder (not just perceived). Then we can ask why. As I've seen in someone's signature around here:
"There is no need to argue if an experiment can be made."
- H. St. C. Deville

NeonPulse - 27-2-2014 at 15:26

im not really sure but it may have something to do with the density of the charge,as well as VOD. A 10g etn loose packed seems louder than 10g of etn cast. in the past i was able to hear a few NM+amine or nitric combinations and the PLX formulas seemed to have an echoing and fast crack kind of sound while the nitric sensitized NM was more of a boom. mhn seemed a little quieter than i expected also. ANNM has a more heady sound than ANFO too. this topic has caught my attention so i think i may do a little research on it ....

Bert - 27-2-2014 at 17:39

We have done tests with identical size (volume, not weight) & configuration but different compositions, with groups of people listening, judging & placeing them in perceived order of "loudness".

The order we shoot them in changes the relative loudness perceived. The distance to those listening and judging changes the relation too- High pitched brissant explosions that get a low placement close up may get a much higher one from listeners far away.

And very seldom do these subjective orders match those done with a dB meter, unless there is a large discrepancy in size/weight between devices.

So, if in addition to all of these factors, you are judging explosions heard on different days and at different distances? I give up. No meaningful data to had here.

Ral123 - 28-2-2014 at 00:10

If let's say 15g flash are heard louder then 25g highly pressed RDX at let's say 15m distance in the open. I'm not convinced at 100m people won't find the RDX louder.

Dany - 28-2-2014 at 01:27

The duration of the shock wave play an important role in how you hear the explosion. When an explosive is detonated, the shock front will propagate in air at supersonic speed. The amplitude (overpressure) will decrease with distance but the duration of the shock will increase. This why you hear a sharp sound when you are close to the detonated charge. the sound will become broader and broader (similar to a thunder sound) when you are farther and farther from the detonated mass of explosive. The comparasion between RDX and aluminized explosive is not correct (even if the charge have the same mass). RDX is a nearly ideal explosive while aluminized explosive like ammonium perchlorate/Al or ammonium nitrate/Al are highly non-ideal and this effect is reflected in the blast wave generated from each explosive. RDX has a higher performance (higher detonation velocity and dtonation pressure) than ammonium perchlorate/Al or ammonium nitrate/Al. However, the later non-ideal explosive can have higher blast pressure due to the afterburning of aluminium in air (aluminium burning is enhanced by turbulence due to the Rayleigh-Taylor instability generated at the interface of detonation products/ambient air).

Dany.

IrC - 28-2-2014 at 02:05

I think duration is a factor but the reason this question seems difficult is due to more than one variable simultaneously as well as the rate of change of variables involved. The rate of change over time of both the volume of gas displacement and rate of change in velocity of the gas molecules. The difference in sound from a safe distance of say dynamite (which hits you in the gut as a large slow pressure wave) and the sharp report of a very fast (high brisance - high shattering capability) material. While considering the way the mechanism in the ear works which allows the perception of sound.

papaya - 28-2-2014 at 13:56

I have a feeling that the shape of the charge as well as the point where it was initiated (where detonator is located) may contribute to the effect, since the propagation of the wave exiting the charge is not uniform in all directions (correct me if wrong). It would be interesting if you try 2 identical cylindrical charges initiated same way from one end, one placed vertically and the other horizontally on the ground such as the end opposite to the initiation is directed to the observer.

Turner - 28-2-2014 at 18:03

Papaya, if this is true, then does a charge lose effectiveness if it is initiated on the side (i.e tape a blast cap to the side of a cylinder of TNT, vs a cap placed in the center in the hole). The propagation throughout the material takes longer if initiated from the side than the center, would the explosive behave differently and create a slightly different affect? How about exploding bridge wire detonator throughout the mass so all material detonates virtually at once?

I think this question came up once and the answer is no, the performance in either case is basically the same... HMMMMM

papaya - 1-3-2014 at 01:24

Honestly I don't know, I just imagined that a cylindrical relatively long charge initiated from one end would yield the strongest wave from the opposite end compared to sides. I want to hear the expert as well.