Would a gunshot echo in a cave?
I'm writing a story in which someone is shot in a cave system. Another character is an adjoining tunnel some distance and at least a few tunnel intersections away. Would the sound of the shot reach her? Would it sound like a gun shot? or a rumble of echos?
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Would a gunshot echo in a cave...
It depends on the cave. To echo a sound wave needs a smooth surface to reflect off of.
Most caves aren't giant smooth caverns but are relatively convoluted or tight passages with random shapes to the walls, ceilings and floors which will randomly reflect the sound and quickly attenuate it.
The shock front of the 'bang' will travel a way, but it too will be attenuated.
Think of a muffler / silencer from an engine exhaust. No smooth surfaces and little noise made.
Within a cave it's hard to hear other people even a short distance away as they make their way through the cave, especially if there's tight passages.
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It turns out that gunshots can be used to map caves,
The decade-long search might have gone a little differently, though, if soldiers had access to a new system that can use sound waves from a gunshot to quickly map unknown caves and tunnels. The portable system, created by David Bowen of Acentech in Cambridge, Massachusetts, consists of two microphones placed at the entrance of a cave or tunnel, which are hooked up to a laptop loaded with software designed to decode acoustic signals.
A gun is fired four or five times, with about 5 seconds between each shot. Fifteen to 20 seconds later the map appears on the laptop’s screen, with simple graphs that display the area of the cave at different distances, and written explanations of the data, such as “30 feet ahead is a large opening”. A portable subwoofer can be used in place of a firearm as the source of the sound waves.
so it is probable that the other person would hear the shot. It is likely that it would be a rumble and not a single noise since there are lots of surfaces to bounce off of in a cave.
Beyond that, it would be hard to say, since people usually don't shoot inside of caves. The noise level will be higher and that will result in damaged hearing.
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So the answer is that the other person will almost definitely be able to hear the gunshot in the absence of background noise. Will it echo? That sounds like it would depend a lot on how much the walls in the cave system resemble the grooves in acoustic tiles from recording studios. Also tunnels that open into large caverns or even tunnels that gradually widen have a damping effect on echoes returning to the source.
The second person in this scenario actually doesn't need to hear an echo, they only need to hear the original sound, and especially if the tunnels are of consistent diameter, they will act to propagate the sound (and the shock) from the gunshot for very great distances. (Meaning the person a few intersections away might also get hearing damage from the pneumatic column between them transmitting nearly the same concussion to them as the person firing the gun)
YouTube is failing to provide good examples, but the next time you see a hollow handrail that's a few carlengths long, ask a friend to 'drum' one open end with the palm of their hand and have your head (not ear) near to the other open end. It makes a sound a bit like a dubstep bass drop and is actually much louder at the far end than for the person making the sound.
Visualising this scenario everyone is in corridor-sized tunnels, the previous answer shows huge cavernous rooms so if you mean could someone at the opening of Carlsbad cavern hear a gunshot by the elevators? Maybe not. That's a long hike between those two places.
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From my experience in caves, I'd say you could expect the gunshot to reverberate for just a second or two in passages that are barely more than walking size. In larger passages, maybe longer. Around a few bends it would probably sound muffled as well. And keep in mind that sound travels through small, impassable cracks and crannies in caves as well -- I've heard the muffled thuds of people crawling through passage hundreds of feet away with no direct path between us.
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