Just saw this video- I hope to one day make movies/television, and when I do, I have ideas of doing so in very non-cliched ways. One big movie/television cliche I learned the truth about was the whole shoot-the-gas-tank-car-explodes one: Mythbusters exposed that that doesn’t happen, or at least for them ,they shot it a dozen times and it did jack :D.
This video, I think, records that high explosives? don’t make a big boom when they go off- I’ve seen other videos of demolishing buildings, and they didn’t make a loud noise either- at least, the explosion didn’t. So do any explosions make a bang like in the movies/tv, or is that just convention?
I think that high explosives generally make a sound that is very loud but very short in duration. The audio track of a vide recording only has so much dynamic range, so you get a sound that is very quick and not extremely loud. That’s my guess, at least.
Right, but the principle’s the same - there’s a large energy release, that displaces air, creating a shock wave. A shock wave is just really loud sound - it’s a wave transmitted by the air, and it even travels at the speed of sound. If it explodes, it has to make noise.
Mere guessings on my part here as IANA explosives expert but the whole deal with leveling buildings with explosives is to use as little as possible, instead relying on strategic placement and pre-weakening to reduce the amount necessary to the bare minimum. Additionally, much of those explosive are buried deep with a drill hole into concrete supports and often they’re wrapped with a special blanket to reduce shrapnel; hardly a fair accounting of their audio potential.
Explosions in real life are way, way, way louder than they are in the movies. I don’t think normal speakers could produce that sound unless they were exploding.
Actual explosions have less orange fire ball than their movie equivalent though.
I’ve got some video of me throwing grenades. The sound isn’t very impressive at all, and there is not big fireball or anything like the movies. But when you’re actually there, the bang is amazing and loud.
Same thing with Claymores. Claymores have 1.5 pounds of C4 and are unimaginably loud. You wouldn’t believe how loud until you actual laid down 30meters behind one and set it off. Holy Crap!!
But again, it doesn’t have the huge orange fireball like in the movies.
If someone will host the grenade video or show me a good site that does that, then I will gladly upload it or share it.
But anyway, it sounds like Hail Ants has it right. Explosions like that are so damn loud that no mic or speaker can properly duplicate it.
One thing about those films of buildings being demolished … they’re shot from a safe distance away. Which means that you will see the explosives go off a long way before you hear them.
Excalibre is quite right about the shockwave thing. “Hearing” something simply means your ears are registering vibrations passing through the atmosphere (or whatever medium you and your ears happen to be in at the time). Detonating high explosives will cause a lot of such vibrations, albeit briefly … Hmm. I wonder, would it make sense to measure explosions on the decibel scale? I’m sure it would be possible to work out exactly how loud a stick of TNT is …
One of my first jobs was as assistant to the powder monkey on a building site. He would show me where to drill, how deep and how sticks of gelignite to put in each. Although the explosions looked impressive they weren’t very loud - just a muffled roar, due to the dampening effect of the rock and soil. I believe that explosives used in building demolition are heavily dampened to concentrate the concussive force.
Most automobile fuel tanks aren’t strong enough to contain the pressures needed to get really rapid combustion of the fuel-air mixture and so don’t produce a detonation. However, they are plenty energetic enough to cause a lot of damage if you are in the vicinity when one ruptures because of the explosion.
I have heard several bombs, including the one that killed former Lebanese PM Rafic Hariri, and they definitely make a sound. The latter was unbelievably loud–it created a shock wave that shook dust from my ceiling, even though I was over a mile from the blast site. That one was several hundred pounds of TNT. In the last several months, there have been a number of smaller bombs in the northern, Christian parts of Beirut, and we have heard a number of them, even though they have been smallish (10-20 kg of TNT) and often 2-5 miles away. So high explosives are loud.
Ditto that – beyond the explosives and grenades I heard during my army service, I heard the bomb that went off at the Tel-Aviv Dolphinarium some 10 years ago. That was just the amount of explosives a suicide bomber could carry in his backpack. I was at home, some 5 miles (!) away, and not “expecting” anything… when suddenly I heard something and asked “what was that?” A few minutes later and one TV set turned on, I knew
As do guns. Having heard a 7.92 Mauser fired, I can assure you that if Hollywood were able/allowed to reproduce gunfire accurately, a fair proportion of the audience of Saving Private Ryan would have permanent hearing damate, and the rest would have suffered a few days of tinnitus.
TV/Movies are not necessarily capable of conveying the reality of a situation very well…
Gunshots and explosions both sound the same in that what they sound like depends on how far away you are. Up close, they sound very shrill, like a lightning crack. As you hear them from farther and farther away, they sound more and more lower-frequency “booming”.
…Most media (TV and movies) use an “enhanced” sound, because the real sound up close only registers as a light quick pop to a typical microphone setup. It doesn’t sound boomy enough. If you ever played or heard the old PC game Rainbow Six, that’s pretty close to what a real gunshot sounds like inside a building (assuming you are wearing -6 or -10dB earplugs!).
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I’ve witnessed a few largeish detonations connected with highway construction. These days such explosions mostly use ANFO (ammonium nitrate & fuel oil) which a detonation expert told me was cheaper and safer than high explosives.
He also said it’s somewhat less violent, and since the explosions happen well underground (in holes bored for the purpuse) the effect is rather muted compared to what you might expect. But there’s still plenty of sound.
Generally though, they’ll foley an explosion in. And when they do that, they generally put the audio over the image. I can think of one film where the sound was ½-second or a full second behind the image – Red Dawn. Near the start of the invasion some characters are standing at a general store or gas station. There’s an explosion in the b.g., but the sound (realistically) takes time to travel to the location.
