6 ms·
"Frost crack" sounds may come from sky, not trees
- Xeyz0r 2y agoInteresting, but kinda hard to believe that the sounds we hear in the forest could be coming from that high up I'm no expert, but if that's true, that's pretty mind-blowing
- maxbond 2y agoThe article explains that this objection was raised by other researchers, but that the sounds were triangulated to a height of about 250 feet (because they are caused by an electrical interaction at the top of an inversion rather than from the aurorae directly).
- ditn 2y agoOne thing that I found super interesting when I studied audio engineering is that our ears are very good at determining direction left/right, but absolutely hopeless at working out if a sound is up or down. This makes their hypothesis a lot more believable to me; I can understand others incredulity.
- ambicapter 2y ago> absolutely hopeless at working out if a sound is up or down Easy, just turn your head to the side :P
- timcobb 2y agoWould be cool if there was a recording, I don't know what this article is talking about.
- maxbond 2y agoSurely the recordings are available somewhere on the web, but here's a short clip I found on YouTube: https://youtube.com/watch?v=cm97VQobbh4&t=435 https://youtube.com/watch?v=cm97VQobbh4&t=435
- deleted 2y ago[deleted]
- yosito 2y agoFascinating read! I'm surprised this wasn't already commonly known.
- pierrec 2y agoThe conference paper (which is very well written and approachable) suggests that the precision of instruments was insufficient to establish this as of 20-ish years ago. See the section "First Experimentations": https://www.researchgate.net/profile/Unto-Laine/publication/380027668_Magneto-acoustic_triangulation_method_for_electric_discharge_localization_in_the_atmosphere/links/664e05d6bc86444c72f6c944/Magneto-acoustic-triangulation-method-for-electric-discharge-localization-in-the-atmosphere.pdf https://www.researchgate.net/profile/Unto-Laine/publication/... Trivia: I tried to copy "First Experimentations" directly from the pdf and this what came out of my clipboard: -*%.$+/01/%*2/#$3$**&#. Thanks, Researchgate
- smegsicle 2y agomore like research gatekeeping amirite
- yorwba 2y agoSeveral chunks of text in that PDF start with the printable ASCII characters from ! onwards in order until there is a repetition, e.g. Magneto-acoustic triangulation from the headline corresponds to !"#$%&'(")'*+&,)-&.,"$#*/"&,'$ which is >>> list('!"#$%&\'(")\'*+&,)-&.,"$#*/"&,\'$'.encode('ascii')) [33, 34, 35, 36, 37, 38, 39, 40, 34, 41, 39, 42, 43, 38, 44, 41, 45, 38, 46, 44, 34, 36, 35, 42, 47, 34, 38, 44, 39, 36] So I think this is probably a PDF font-encoding issue that might've already affected the author's original upload.
- pierrec 2y agoYou're right, I immediately assumed some annoying DRM, but after looking it up, it does seem more like a bug. I couldn't find any clear explanation for why it happens though.
- mistercow 2y agoWouldn’t the tree explanation be refuted by simply recording the sounds in an open field, far away from trees?
- florbo 2y agoBut what if the discharge requires some specific environmental factor, say, something the height of a tree?
- deleted 2y ago[deleted]
- greenbit 2y agoMaybe tree covered ground makes a more effective source of the rising-up component of this process. That relatively warm, negatively ionized rising air might be much diminished over a frozen lake or open plain. Otoh, it'd probably be greater over the ocean, I would think.
- deleted 2y ago[deleted]
- satori99 2y agoDo people at Antarctic research stations ever hear this sound?
- deleted 2y ago[deleted]
- bongodongobob 2y agoProbably not as it requires a gradient, which that deserted and static landscape wouldn't provide.
- Willingham 2y agoIn grade school I read a book called ‘The Hatchet’. It was a story about a man who survived a plane crash near the arctic circle and had survived many days on his own with not much more than a hatchet. He experienced these sounds after a number days in the harsh wilderness and thought it was gun shots and that he was going to be saved. The book then went on to explain that it was the trees cracking from the extreme cold. I was mesmerized by this as a kid. Knowing now the true origin of the ‘frost crack’, I’m twice as captivated.
- j_bum 2y agoA small nitpick, the main character is only 13 years old. Great book!
- teruakohatu 2y agoA good book, I also read it as a child.
- ARob109 2y agoThat’s the alternate story line as told in Brian’s Winter. He did not ordeal the winter in The Hatchet. One of my favorite books as a kid, just recently read Hatchet to my boy
- move-on-by 2y agoI just read the synopsis, I’m curious what age your son is or how old you were when you read it? I’m not sure my son is old enough for it.
- karaterobot 2y ago> It’s not to say that trees don’t crack—but rather that spooky noises long attributed to trees may emerge from the night sky itself. Well, it seems like he demonstrated that the night sky itself can make sounds under certain conditions, not that these sounds are always the night sky. By the way, I don't recall ever hearing the supposed tree cracking sound in an area where there were no trees. If it's always just the sky, you'd expect to hear it at least occasionally on the plains, or coming from 250' in the air above you when you're on a frozen lake.
- rini17 2y agoDepends whether the landscape is prone to inversions. They happen most often in wide and enclosed valleys.
- dylan604 2y ago> or coming from 250' in the air above you when you're on a frozen lake. If you're on a frozen lake, you much prefer the crack coming from above than below.
- deleted 2y ago[deleted]
- greenbit 2y agoAnd then of course, there are the "ice making" sounds that do come from below. And different lakes and ponds even seem to have somewhat different voices in that way.
- idatum 2y agoAnd something equally chilling -- the sound of a glacier cracking (more of a deep thud sound).
- deleted 2y ago[deleted]
- maxbond 2y ago
- mattdesl 2y agoReally fascinating. After reading a little more, I learned that while Laine proposed the inversion layer hypothesis in 2016, the Auroral Acoustics group he headed was informally started in 2000. The reason the linked article is coming out now is due to Laine’s latest paper that details the triangulation of the sounds[1][2]. Would love to try and record this myself. I’ve been recording some VLF “sferics” for some time now for an art project[3]; it seems the auroral sound recordings often peak in the same frequency range (and perhaps there is overlap without me realizing it). [1] http://research.spa.aalto.fi/projects/aurora/index.html http://research.spa.aalto.fi/projects/aurora/index.html [2] https://www.researchgate.net/profile/Unto-Laine/publication/380027668_Magneto-acoustic_triangulation_method_for_electric_discharge_localization_in_the_atmosphere/links/664e05d6bc86444c72f6c944/Magneto-acoustic-triangulation-method-for-electric-discharge-localization-in-the-atmosphere.pdf https://www.researchgate.net/profile/Unto-Laine/publication/... [3] https://www.mattdesl.com/sferics https://www.mattdesl.com/sferics
- goda90 2y agoAt first I thought this was going to be about frost quakes[0], which are mini quakes we get in the Midwest when there's a deep cold. [0] https://en.wikipedia.org/wiki/Cryoseism https://en.wikipedia.org/wiki/Cryoseism
- bankcust08385 2y ago[flagged]
- throwawaycar 2y ago[dead]
- whatshisface 2y ago>As this warm air collides with cooler air from above, it forms an “inversion” layer of warmer air layered over cold air, which traps the ions. I think this is reversed, inversions are usually cold air sitting atop warmer air. (Warmer air is lighter, defining the typical sequence with which an inversion is relative to.)
- histriosum 2y agoYou aren't quite right here. Temperature inversions are when the atmosphere warms as you go up instead of cools. The atmosphere usually cools at a fairly constant rate as you go up, at least in the troposphere. This layer of warmer air aloft acts as a cap, limiting vertical motion from rising air parcels from below (which are cooler than the air aloft and thus cannot rise through the inversion).
- soared 2y agoYou are correct afaik - warm air would not trap cold air below it as it would move up, only a layer of could air could trap warm air below it. Some visualizations show air cold/warm/cold, where as others are just warm air under cold air.
- e44858 2y agoInversions usually happen when the ground is cooling faster than the air above, due to radiative cooling. That results in a layer of warm air sandwiched between cold air above and below.
- viherjuuri 2y agoIt was so weird reading a science article that uses feet, and even more so since the research was done in Finland.
- aaron695 2y ago> Laine was able to triangulate the origins of the sounds from calculations based on the distance between the microphones and the speed of sound. The triangulation data revealed the origin of the sounds was indeed the sky. Triangulate doesn't work, it's in the sky remember? You need 4 for 3D space theoretically. But in practice it's more like 6-7. Any wind or temperature difference adds dimensions which you have to computer away. The paper seems to confirm it's literal. 3 mics. Which is fine to find stuff but why not do it to spec in the real paper, do the results disappear? They talk about "virtual microphones", not convinced.
- deleted 2y ago[deleted]
- lrasinen 2y agoThree mics and a loop antenna. The diagram in the May 2024 implies the mics provide a trajectory and antenna-mic difference fixes it in 3D. Disclaimer: I was in his Basics of Speech Processing class in the university. One of the best (and funniest) courses I had.
- sho 2y agoThis reminds me of "aircraft wake snapping" or "vortex snapping", which is a very audible sound one can sometimes clearly hear shortly after a plane passes over you if it's low enough, such as on final landing approach. I seriously thought I was imagining it the first few times I experienced it - so weird to hear sound coming from apparently empty air. edit to add an example: https://www.youtube.com/watch?v=UA-NONhZIN8 https://www.youtube.com/watch?v=UA-NONhZIN8
- zakki 2y agoFor someone living in equator the article will be perfect if it has the sound mentioned in the article.
- deleted 2y ago[deleted]
- vnorilo 2y agoFirst I heard prof Laine talk about recording auroras in the early 00s I and many of my student friends thought he was an old eccentric (in some less polite words too). Seeing him come through with such a solid long term effort, rigorously done and communicated with clarity is amazing, with a pinch of healthy embarrasment. (I studied in the same academic cluster of music/audio/acoustic labs he made his career at)
- sethammons 2y agoMy first thought was "bullshit, these are _obviously_ trees cracking." Well, using triangulation, it is obviously coming from 250+ ft in the air. Good to test assumptions!
- sandworm101 2y ago>> Indeed, these loud cracking sounds are often attributed to large pressure splits in tree trunks, caused by sap freezing and expanding inside the tree’s interior. But while freezing sap in trees has been found to produce sounds at ultrasonic frequencies, outside of the range of human hearing, scientists have found no evidence this phenomenon might make sounds that are audible to the human ear. Personally, i have not just heard them but have seen it happen. At -40 and below, in certain evergreen forrests not used to such temperatures, a tree can randomly "explode". An internal crack shakes the tree, throwing snow everywhere. It lookes and sounds like an explosion. You hear gunshot and then see the tree shake off all its snow. The tree stands out as the one dark with branches no longer held down by snow. It is like an angry ent waking up about to eat a passing human. https://youtube.com/shorts/oG-N2LCYEc4 https://youtube.com/shorts/oG-N2LCYEc4 Does anyone really believe that a crack like that wouldnt make a gunshot sound? Here is the sound, after about 0:30. Not much snow to shake off but you can see them moving. https://youtu.be/Rz3TqqNkEBU?feature=shared https://youtu.be/Rz3TqqNkEBU?feature=shared
- krona 2y agoI'm amazed that this phenomena is hitherto unexplained when it's entirely common knowledge in rural scandinavia, barely worth talking about.
- tnias23 2y agoWhat’s common knowledge in Scandinavia? That the sounds come from the air, not the trees?
- snozolli 2y agoIn February 2021, in the Willamette valley of Oregon, we had a weather event unprecedented in my lifetime. Winters here are usually overcast and rainy, with little to no snow and a handful of mild freezes. In 2021 we had a significant rainfall followed immediately by a deep freeze due to a polar vortex. That morning was like nothing I've ever experienced. About once per minute there would be a loud crack like a gunshot, coming from all directions. After several days, power was restored, the roads were cleared, and it was obvious what happened. Countless deciduous trees had split from what I assume was the accumulated water from the preceding rain storm. There were so many downed and permanently damaged trees that it took around a year for property owners and the city to finish cleanup. Usually, when we get freezing temperatures, it's because there's no cloud cover. It's extremely unusual to swing from heavy rainfall to a deep freeze like that. Anyway, I don't know if this article is talking about something different, but the cracking I heard was definitely deciduous trees cracking due to expanding, freezing water. Few conifers were damaged.
- RecycledEle 2y agoNonsense. If you hear a loud crack and are near trees, look up and get out if the way. This idiot is going to get people killed.
- __MatrixMan__ 2y agoIs it possible that the inversion layer creates a structure for sound to reflect/refract back down towards the sensor, when it in fact the original source was on the ground? You might not detect it laterally if there were a bunch of trees in the way.
- deisteve 2y agoFascinating. Wonder if this is related to these "sky trumpets" reported around the world usually near forests and mountains https://www.youtube.com/watch?v=081FuoN8K40 https://www.youtube.com/watch?v=081FuoN8K40 https://www.youtube.com/watch?v=gtLNmdZTf_g https://www.youtube.com/watch?v=gtLNmdZTf_g https://www.youtube.com/watch?v=PJpucJkRa6c https://www.youtube.com/watch?v=PJpucJkRa6c https://www.youtube.com/watch?v=_P4XOiMKLhk https://www.youtube.com/watch?v=_P4XOiMKLhk https://www.youtube.com/watch?v=gHeoPMg3_zM https://www.youtube.com/watch?v=gHeoPMg3_zM https://www.youtube.com/watch?v=stISzPngwh4 https://www.youtube.com/watch?v=stISzPngwh4
- more_corn 2y agoThis is so neat. I love science.
- Ostrogoth 2y agoThis reminds me of a time I was stargazing, when suddenly a meteor streaked overhead making a distinct sizzling/hissing sound that tracked with its movement…which seemed improbable since light obviously travels faster than sound. I later read the theory as to how this phenomenon occurs is that the sound is created by low frequency radio waves. https://ethw.org/Electrophonic_Meteors https://ethw.org/Electrophonic_Meteors
- __MatrixMan__ 2y agoAnother thing that uses radio waves in the human hearing range is the invisible fences that cause shopping cart wheels to lock (7kHz, visit begaydocrime.com to hear the corresponding sound). Those don't involve sounds in normal operation, so I wonder what about these is different. I would guess that induced current is making a sound in some nearby infrastructure and not directly in the head of the observer.
- fagrobot 2y ago[dead]