Cave Acoustics

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Cave Acoustics

Postby hiflier » Jan 16, 2016 5:23 pm

Hello All.

This is my first post. And I am not a caver per se though I've been in them as a visitor. They are.....marvelous features! I still have questions though and in my mid sixties I thought I'd like to finally pursue some of them :) The first is regarding sound. I've read some through the Forum but I haven't run across any about whether or not sound from outside a cave reverberates inside one in the sense that the sound is attenuated or somehow otherwise magnified.

I realize every cave is different and any dynamics along these lines might vary greatly but does anyone have any opinion or any experiences to share. Or maybe have done any experiments set up to test to see if there is a special dynamic for outside sounds entering a cave? Thank you.

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Re: Cave Acoustics

Postby GroundquestMSA » Jan 17, 2016 11:14 pm

Cave acoustics are mysterious. In a cave here in Ohio we can, in one passage hundreds of feet from the entrance, clearly hear outside noises like car doors and people hollering a half-mile away (there's a swimming hole there). On the other hand, cavers can sometimes be separated by only a few dozen feet and be out of shouting range. Depending on passage size and shape and material, there can be lots of echoes. I don't know if outside sounds are amplified inside caves, though waves from overhead traffic or equipment are often carried through rock.
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Re: Cave Acoustics

Postby graveleye » Jan 18, 2016 8:59 am

Cave acoustics could be considered a product of pure chaos. There are no straight lines and all caves are different in shapes and sizes, not to mention the further randomness of that which is found within - formations, breakdown rocks, boulders etc. Some places are acoustically dead and some places reverberate like mad.
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Re: Cave Acoustics

Postby msharitt » Jan 18, 2016 10:06 am

I can't remember any of the groups name now that I'm trying to think of them. Some of them may be on here and see this or some may know who I'm talking about. But around 2 1/2 years ago I was at Snail Shell. There was a group of maybe 10 that we camped next to. They had the works with them. Canoes, AV equipment, battery packs, the whole 9 yards. After talking with them they said that's what they do is create audio and video recordings in caves. They told me that Snail Shell was one of the best. I didn't get into it with him about what made it the best. But he could tell you exactly what difference done what and how it affected sound. Real nice people, if this was you and you read this let me know. I'd actually like to see how some of that worked out?

I'm sure these guys knew what it took to make it worth it. Anyone who's been to Snail Shells knows the haul system set up just to get large amounts of gear down without walking the ledge. It took them a few hours to get everything down.
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Re: Cave Acoustics

Postby GroundquestMSA » Jan 18, 2016 11:19 am

msharitt wrote:they said that's what they do is create audio and video recordings in caves. They told me that Snail Shell was one of the best. I didn't get into it with him about what made it the best.


Deep water + big passage = huge echo...
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Re: Cave Acoustics

Postby msharitt » Jan 18, 2016 11:56 am

That makes since, I didn't want to speculate though. They went in the upstream passage. I'm assuming the nice hollowed out top with few formations helps as well. It is quite an interesting subject. One which I haven't had the time to devote to studies. I am curious if there is a set formula to determine reverb and echo depending on the open air space? Or maybe even the depth of water?
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Re: Cave Acoustics

Postby hiflier » Jan 19, 2016 12:08 am

Thanks everyone. And I'm sure shape and size along with the material structure is just a part of what make some reverberate more than others. I should be honest about my inquiry which I'm fairly sure to receive more than a little eye rolling. Please keep in mine that this is for me personally and I say that because I wouldn't want anyone thinking that I'm trying to introduce anything weird. I belong to a Sasquatch Forum. I know that there scant if any evidence of this legendary creature utilizing cave on a permanent basis but if they exist I think they might use cave systems to remain elusive.

That said it occurred to me that the huge howls folks report coming across valleys and such may be the result of using caves as megaphones and in the reverse can hear things approaching from outside better when they are inside because of some unique acoustic properties that some caves have.

I'm zeroing in on the caves in the Kiamichi Mountains in Oklahoma as well as some of the lava tubes in the PacNW....Now you know. If it's time for me to leave the Forum I will absolutely oblige- BUT I HAD TO ASK :)
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Re: Cave Acoustics

Postby GroundquestMSA » Jan 19, 2016 11:57 am

Aww, do hang around. Maybe you should get some first-hand caving experience. That might give you a feel for the plausibility of your theory (it has a few problems :waving: ).
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Re: Cave Acoustics

Postby hiflier » Jan 19, 2016 7:30 pm

Shucks, at almost 67 with a <ahem> small heart condition I don't see myself as being the poster child for spelunking LOL. None of you would have me hanging on one of yore ropes and who could blame you? Last October though I was 3 miles in with a 35 lb. pack at Baxter State Park in Maine though so maybe....

Anyway thank you for not out and out heckling me. I'm actually skeptical of the creature's reality but do lean more toward s it. I will say this though: as a result of pursuing the subject I've learned so much about wildlife, habitat, the environmental sciences, DNA, and Human origin and a TON about bats. And now I'm going to learn about caves. There's something to be said about autodidacts. It under rated in my case. Thanks again for the welcome and the beckon to remain. Makes me want to find a Maine grotto to tell you the truth :) Nice to be here and I do want to learn more about cave acoustics. I also respect your sensitivity the bats. Such tiny, sensitive, necessary creatures and so so unique. The WN virus syndrome is very upsetting.
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Re: Cave Acoustics

Postby l lambert » Jan 20, 2016 12:44 pm

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Re: Cave Acoustics

Postby hiflier » Jan 20, 2016 3:34 pm

Interesting account, thanks. Just before Christmas I was on the phone for two hours with a 63 year old experienced researcher. He was on a team looking to actually shoot one for the purpose of providing a voucher specimen to science. His team mate had one in a night vision gun sigh =t for eight minutes and when told to shoot it he said he couldn't- it looked too Human. I don't think the guy I spoke to was lying. He went on to say the shooter informed the team that he was never going back. Now I don't really know what to make of any of this. I certainly have no truck with any people who want to spread any woo. If this is a real flesh and blood creature then I think that in places they use caves. The guy I spoke with was convinced the cave systems in the Oklahoma Kiamichi Mts. were being used in this way.

But this is a cave Forum so the one thing I will mention is that in that BFRO report the loudness of the howl is what struck me. It is is that aspect I'm trying to research by understanding cave acoustics. It will prove nothing of course so the subject as it emanates from a cave or the ability to hear sounds from outside that are sourced some distance away is something I will be happy enough to learn about. The creature itself? Meh. It too is an interesting subject but it is whatever it is.....or isn't ;) Thanks for that link. Much obliged. :grin:
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Re: Cave Acoustics

Postby trogman » Jan 21, 2016 4:20 am

Sasquatch don't dare venture into caves- the Hodags would kick their butts! :bash: :laughing:
Seriously, though, it is an interesting topic. Us cavers are certainly intrigued by mystery and the unknown. That's why we venture into deep, dark places in the earth.

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Re: Cave Acoustics

Postby hiflier » Jan 21, 2016 10:30 am

I would like to round this out a bit by explaining one more reason I'm interested in the cave dynamic. It's not just for sound but for the bats that choose certain caves for their hibernation. A lot of this many of you already are keenly aware of so I'm mentioning it for any cavers that are new perhaps and have some questions regarding responsible bat etiquette. Some interesting things regarding this subject. Bats don't just pick any cave to hibernate in. The temperature inside is critical in allowing them to slow down their heart rate, drop their own temperature and slow down their respiration rates. If it's too cold they will burn up too much energy. Too warm and they won't be able to lower their metabolisms. Also they are not really asleep and are always aware if something enters the cave either by light or by sound. The bats WILL begin wake up but it can take hours for them to fully become functional.

They will rouse on their own occasionally to defecate, drink water and such but again it takes a long time to reach their naturally active level for movement. They may look like they are still asleep to someone who wanders in but they aren't. If disturbed enough or often the bats will leave the cave and go somewhere else. If Sasquatch does use caves in winter then it could be because of being able to help sustain themselves minimally by eating bats. The bats are helpless in their hibernation state and will be for hours but if disturbed during winter they could rouse enough to leave and if they do they will die. There are reports of people finding dead bats outside of caves.

The reason I'm bringing all this up is that if Sasquatch uses caves then they will only use them if there are bats? An idea I am actively chasing down. If the bats leave then so will Sasquatch? Do they follow the bats to see where the new cave is and then when a new winter comes move in to continue foraging on bats? Is this why there doesn't seem to be permanent dwelling evidence in caves? I'm proposing that the reason they are temporary could be that they follow the bats who have left because of Sasquatch's own presence.

When their natural food supply becomes unavailable in winter and Sasquatch gets hungry no problem- just pluck a few bats off the ceiling. I joke about it sure but I am trying to develop the idea. IF they exist I think they do pluck bats from the ceiling as long as they can reach them or maybe use a stick to pry them loose. The bats of course won't tolerate the disturbance and depending on how much winter is left will leave once they are roused enough to respond.

If roused bats, who only store a very small amount of fat, burn more of it and in doing so can actually starve to death before the insects they feed on hatch out. And extremely delicate balance to be sure! I've read articles where aware cavers don't explore during the winter months in bat caves. My hat is off to those folks. This is already to long so I need to stop; there's more to say however and I promise to try and keep things short from here on. I've also enjoyed reading some of the other threads and discussions too. Lots to learn.
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Re: Cave Acoustics

Postby GroundquestMSA » Jan 21, 2016 2:27 pm

Has anyone yet blamed Sasquatches for the spread of WNS?

hiflier wrote:There are reports of people finding dead bats outside of caves.

Very commonly over the past few years. One effect of pd. is that it "wakes" the little fellers and they fly about/starve/die as you describe.
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Re: Cave Acoustics

Postby hiflier » Jan 21, 2016 3:02 pm

GroundquestMSA wrote:Has anyone yet blamed Sasquatches for the spread of WNS?


Not as far as anything I've read but I can spread the word. :shhh: what a great-out-of-the-box thought. I certainly seems to be a factor regarding other animals. If any of that can become part of the picture I've been forming then perhaps some of the bars placed across cave opening aren't just for Humans LOL. In reality it could very well be for any animal biped or not including us since before this really came to light there may have been some cross contamination from clothing of gear? It's easy to see fur doing the same thing and perhaps worse. Wild animals who might inhabit caves are for the most part territorial unless something like the large fires in the PacNW or drought uproot them or destroy what they feed on. There are species of eastern bats too that do migrate west. It does in any case appear that the WNS is an airborne virus.

It's going to be tough to get rid of this one but as far as insect populations go it has to be controlled somehow. :off topic: Don't worry, I'll get back onto topic here next post. This has truly been interesting to learn about though.
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