Physicist here. My first thought is that it's thunder. The heat of the flame expands the air that it moves through, then as the air rushes back in, the air that was on one side collides with the air on the other side, then it recoils, then rushes back in, etc, resulting in a short-lived oscillating pressure wave... a sound wave! It also explains why, as the flame gets smaller, the sound gets higher pitched. The frequency of this effect increases because it takes less time for the air to rush back in and create the oscillating effect that we hear as sound. There are probably multiple things going on here, too, so other explanations are also gonna have a lot to do with it!
I was thinking a similar thought, but also that the molten plastic is spinning as it’s dropping, or at least it looked like it was, which could play into the core idea. The flame comes off the plastic asymmetrically which causes drag on the atmosphere around it and applies an small force on the plastic causing it to spin on its falling axis, the further it falls the faster it can spin causing the pitch to change the longer it falls. Maybe the other plastics that didn’t make a noise were too heavy and don’t allow this rotation to take effect? maybe they’ll take more effect at a higher distance? Great, now we have more questions and still no answer 🙈
Not bad, but it's almost definitely the flame front being pushed down from the front to the tail of the droplet with the gas and then recombusting as the gas rebuilds
@@beyondtheillusion333I think this is definitely a part of the effect, perhaps the fact that it was melted from stranded or thin plastic gets small air bubbles trapped inside and as they heat up they expand? Something with the volatiles in the molten plastic has to be a factor...
@@omegahaxors9-11 You should upload the video to your channel for us to see, whether you meant that you recorded your own high speed experiment or tried recording something playing the above video with a high speed camera like I assume you are trying to say, which would actually be just as interesting to see, honestly.🤔 *edited for clarification
You made a version of a thing called a "zilch". I saw the upscale version in the late 70's as a kid. The proper way to make one is to take any similar plastic, like a trash bag, pull the bag to make it as narrow as possible then tie knots it it a few inches apart. Hang it up somewhere about 3-4 feet (or more) off of the ground above a white plastic 5 gallon filled halfway with water. This is best when done at night. You get the "zilch" noise from the melting plastic falling and a small flash as it enters the bucket prior to extinguishment. The knots create a moment of rapid "zilching" since the knot is a concentrated area of plastic. The rippling sound (zilch) is the fluttering of the wind trying to put the flame out but the plastic is able to resist due to the heat at which it burns and turns to a liquid. The hot, burning liquid is slightly resistant to being blown out like a candle. There is a layer of the melted plastic around each droplet that in effect, boils. As I understand it, this was best used in outside events by older adults where the consumption of natural herbal remedies took place. As a kid, it looked and sounded cool.
G,day mate old Aussie Boomer here, way back when I had to ride a kangaroo to school I made a thing with the help of my mum called a pyrophone (60s) that weird old thing had a similar sound. Keep the weird alive old fellah and all the best to you and yours from Jedro the Grate
My 2 cents as a guy who researches fluid dynamics, when spheres or other bluff bodies go through a fluid (air) it causes vortex shedding which also causes acoustics at the same frequency as the shedding. The frequency of the shedding is described by the Strouhal number, which should stay constant if the shape of the body does not change. Strouhal# = freq*diameter/air velocity. My theory is that as the droplet falls, it causes this shedding and acoustic frequency that you hear. As the droplet accelerates and as the diameter decreases from the burning, the frequency must rise to maintain the Strouhal# causing the fwooiip (low to high freq). Non bluff bodies do not cause vortex shedding, so if it is too slender (perhaps in the case of a less viscous plastic) than it wont cause it, though with a flexible tail it gets more complicated. Not sure about those details, though I think usually the tail accelerations would take energy away from the acoustics unless some resonance is there. Perhaps if the plastic is more flammable, it may burn the tail before it can become a slender body, or simply makes it smaller and thus reduces the acoustic dampening it probably causes? Or if the droplets start too small and generate only high freq noise, since most of its energy is in the frequency rather than the amplitude we can't hear it? I also assume the fire has some affect on amplifying or facilitating the sound, because I don't hear this for rain or other things. Heat increases the speed of sound, so perhaps any sounds created in the flame get compressed together at its edge as they hit a slower medium and thus increase the amplitude of the acoustics?
@@randolphfriend8260 I guess any more info would be nice but just knowing that the flame is extremely hot compared to its surroundings is probably good enough to know on that idea (though maybe the ratio of temp could give you an idea on the internal shedding freq to audible freq ratio assuming this ideas holds water?). I'd be more interested in how the flame and droplet move around while falling to create the sound waves.
@@randolphfriend8260 looking at the scar on the back of my hand from one of these melty torpedoes 40 years ago or so I can attest that its pretty dang hot! the shape of the scar is tear drop so it had a tail. I remember getting splattered as it went by so it most likely was boiling as well.
There's an old singing exercise using candle flame to learn control of your diaphragm. You light the candle, and try to almost blow it out, but without actually blowing it out completely. When you get it right, it makes a very similar sound to this, fluttering and sputtering. And you can see the movement of the flame and smoke coming off of it. It looks a lot like slow motion video that I've seen of various wind instruments like flutes, recorders, and whistles. When the light is right, you can even see the vortices in the smoke blowing away from you.
THAAAAANK YOU for doing a video on something you dont understand and admitting that you have no idea and want to know. People seem to think that a scientist needs to know literally everything and has no room to learn or grow. We all know so little. Its nice to see scientists saying "yeah i have no freaking clue. All i can do is speculate." While showing pure, unadulterated fascination with their lack of answers. Thats what science is ABOUT is being fascinated by unknowns and trying to find answers, not automatically knowing everything somehow.
We call this "Zippers"! Its caused by shedding "Vortex rings" of vapor of one side and then the other. The size if the vortexes is relatively constant. However, as the drop accelerates in speed due to gravity the frequency, naturally, increases. Hence the Zipping sound. redrok
My thoughts exactly. Also... I notice even visually the flame has a ripple in it... like a flag in the wind. It whips back and forth. If viewed in slow motion I am willing to bet that the frequency of the ripple matches the frequency of the pitch of the sound. As the "wind" speed increases (speed it is falling) it increases ripple frequency. In fact I would put good money on that bet ;) *Side note... I have even heard and observed this same thing from a candle in a room with very still air. The updraft will cause this same effect and produce this same rippling and a similar sound. I came to all these conclusions way way back then in my younger days lol
@@raw760 I used a plastic bottle and got a 3rd degree small burn on my leg has a guts of wind push it in the wrong trajectory hopefully the drop was small but still the pain made me never do it again. And I clearly remember this strange noise it was making.
i used to burn the end of a plastic knife and drip it on my arm to freak ppl out (i was that idiot). It would burn perfectly round circles thru the top layers of skin leaving only a completely white hole - but no pain at all (must have got all the nerves?) Now i have a dozen small circle scars on my arm that i have to explain to my kids :/ Dont try at home
Found this sound when I was a child and we needed to start a campfire while very wet. We lit a plastic milk jug and as it dripped it made that distinct sound. The plastic was able to light the campfire and we stayed off hypothermia and learned that cool noise.
As a boy in the '60s who played without benefit of adult supervision, I too discovered the unusual "vvvvvVT !" sound from the drips of burning plastic milk jugs.
This takes me back. At the campfire, as a kid, I'd take an empty foil topped sugar water container (those bright colored drinks your mother buys because it seems healthier than pop) and light it in the fire.on the end of a stick. Then you get the 'vvvvvt' sound when you hold the stick and let the molten plastic drip.
I used to put " Blue tip " brand strike anywhere matches in my BB gun and fire it into a solid nearby. No bb, just the match. Almost everytime, the match exploded like a firecracker. Of course, if you fire from more than about 2 or 3 feet, it would tumble and not strike with the tip. I never see these matches anymore. I guess for a safer match, they made them only strike on the box. I used to buy the 750 match boxes in 3 packs. Cheap entertainment. Also at night, I placed a flat rock at end of barrel with a very slight tilt. The match would strike this stone on its way to the sky, like a cheap fireworks. You must be careful where you do this. That match may still be lit when it lands and the winds could carry it a ways. In fact, I had one that failed to light after firing and a few seconds later I see it light when it landed on a neighbors shingle roof and tumble to the ground and light some leaves. I ran down the alley and stomped it out. That was about the time I stopped doing this trick. lol
in my opinion this is the same phenomenon that happens when you try to blow out a fire that just refuses to extinguish. there has to be a partial or complete extinction of the flame and a rapid reignition of the volatile gasses by sheer temperature (keeping in mind the plastic itself isnt burning, rather it is the volatile compounds that get released by heat). the ignition will make a small "poof", and the repetition of this on and off cycle will make a longer sound with a frequency that correlates with how fast it is happening. this will put size, type of plastic, etc. into the equation
That was my thought, that it might be similar the the buffeting whoosh or roar a flame makes when you vlow on it, but the pitch is much higher when the fuel source is smaller and the flame can oscillate faster. But that doesn't resolve the mystery about why some plastics don't make the sound. I wonder if dropping the denser plastics from a greater height might get something out of them...
@@cliftut It's a function of the surface area of the falling material. The denser materials all create finer drops which exposes a smaller burning surface area to wind buffeting. All of the less dense burning mediums produce larger droplets, which means more surface area to burn, which means more flames that are resisting the extinguishing force of the wind speed. If you've ever blown on a campfire or candle, it's literally just the distorted sound that fire makes when you're blowing on it. As the drop accelerates, the pitch of the distorted sound increases with the falling speed of the drop because the frequency of the distortion increases relative to the wind velocity. So the rising 'zip' sound is caused by the acceleration.
When my house was burning, I was going down the steps. Just before I put my hand on the rail. A drop of burning plastic fell on it. I then put my hand right on it! Not leaving it long! My hand on fire, I try putting it out on my jeans. Luckily it was only a half dollar size flaming ball of plastic! Most of it went between my fingers! Seeing that brings back memories!! When the blister popped, I had a huge hole in my hand, compared to the area. It had to be a 3rd degree burn. I can still see the scars, looks nothing like the burn, it was mostly deep than wide, and being between fingers. make it seem smaller! Careful and Good Day!
I had to pause the video at the beginning to comment. Back in 1964, when I was about 7, I was a Hot Wheels freak. Remember those little cars that you would roll down the orange strips of track that snapped (slid) together? Well, I discovered that if you light one end on fire and let it drip it made the most amazing and awesome sound that I have heard to date! I couldn't stop! I ended up with no track...only a bunch of cars left. I WILL NEVER FORGET THAT SOUND! I even climbed on the roof so it would last longer...then a tall tree...the sound lasted for quite a fall and increased in pitch as it fell. Thanks for the trip down memory lane!! --dAlE
I first heard this sound back in the '80s. All of the neighborhood kids hung out in the woods behind the houses. There was a sand track back there where they would ride dirt bikes. That's how it got it's name, The Sand Pit, or The Pits for short. We would occasionally have campfires out there. One day while I was roaming around by myself, I started burning random things, as kids do. When I got to an empty milk jug, that's when I heard this amazing sound. I have never heard it again until today, but that little zip, zip, zip sound always stuck with me.
Speaking of sand, it makes a similar sound when you walk barefooted on the beach. But yeah, as kids we would light bags on fire and marvel over the sound it made when it dropped. Ah, the simpler times.
One material which makes a great example of that sound is the plastic ring structure used to hold together six-packs of cans. I don't know what mechanism is making the sound, but as the drop accellerates downward it makes the sound go higher in pitch. I imagine that the moving air makes combustion more difficult, so you get a small buildup of unburnt gasses. Then when enough of the vaporised plastic has built up, you get a small flare of flame. The zipping sound is a series of ignition flares, which grow faster as the air speed around the drop increases.
Used to do this as a kid. Burned myself several times. The molten plastic would remain stuck to your skin for a couple of weeks. My favorite material was that stuff they bind cardboard boxes with. They look like thin flat belts and come in many colors. They also make mini explosions when they hit the water.
My theory is that the sound happens because the falling effectively creates a powerful updraft and the heat/pressure differential from the fire on the drop could fuel a vortex with the right conditions. Essentially, the falling drop creates a vortex that gets tighter and faster until it collapses or the drop evaporates.
My guess is, because of the looser composition and different properties of the polymer chains that make up the plastic, some burn faster than others. In the case of nylon or styrene, they burn fast, so as the drops fall, the top of the flame at any discreet moment is unsustainable and its density is closer to that if the ambient air. In a visual sense, the top of the flame is "thinner" than the bottom, like mousse vs pudding. Because it has less influence on the surrounding air, the eddy currents produced by the mass of the flame below can whip the tip of the flame back and forth, producing sound. The faster the meduum burns up, the less matter will be feeding to the top of the flame, making it weaker (less massive) and more able to be pushed by the eddy currents due. Because the lower mass allowes for faster acceleration, faster burning mediums will produce a higher pitch die to the faster motion of the flame tip. The slower burning the plastic is, the lower the pitch will be. This is why the very flammable styrene made a (guess) 300hz buzz, ehile the nylon, a slower burning medium, made a 60hz buzz. If dropped from a high enough place, the acrylic and hard plastic will also produce a sound, just lower than we can hear at first. As they burn up more fully at the bottom of the fall, they will also start to produce an audable sound. As they will have a more massive (amount of matter) flame to move as they drop, so the sound will start low and quickly "WOOOSH" up in pitch as the remaining plastic burns more fully and the flame becomes weaker. A candle burns by using capillary action to feed the paraffin or oil to the wick, because there is a steady source of fuel, the flame stays strong. But when the fuel runs out, the flame gets weaker until it goes out. The weaker flame is less dense and will thus flicker more if the ambient air is disturbed. This is the same this that is happening as the plastic falls, it's using up the last of its fuel, but at different rates for the different plastics. The faster it loses mass, the higher the pitch becomes. For a good visual idea of what's going on with the flame, Schlieren photography is a method of lighting that allows you to see the patterns of air and subsequent eddy currents around the flame. It also makes for a good demonstration. en.wikipedia.org/wiki/Schlieren_photography?wprov=sfla1
My random guess - the woven nature of the rope causes strands to stretch as the melted section detatches and falls. The strands vibrate in the air causing a sound. As they burn, they contract and the pitch increases (plus acceleration).
I think you're right. Anything related to just vortex shedding or flame dynamics doesn't explain why it only works with woven material. This could be tested by examining the drops left behind in the water. I think you're right about them getting shorter too, the pitch change seems to accelerate and they probably have a low terminal velocity anyway.
That's a sound I want to start hearing Sound Engineers use for all sorts of things. Like I can imagine mixing that sound into the mating call of some kind of fantasy frog or something.
The VOIP! Found it a few years back taking a lighter to 6-pack rings. (For no good reason other than I'd drunk at least 6 sodapops.) I've tried to show friends its magic, but with only mixed success. I'm very happy to know others have heard the voip and wondered about its mysteries as I have.
We used to melt army men as kids. Made a really good sound about the same as the nylon rope. Think a high speed would show the glob of plastic oscillating. The ones that don’t make noise the glob is to dense and doesn’t oscillate.
4:59 It really feels like the falling solid bits feed extra air into the flame and it's just like blowing at a candle and bringing it to the point of nearly going out, simply fluttering in the "wind". Different compositions would burn better and thus better keep the reaction going. -edit: I think Steve Mould should be made aware, if he's not already on the case.
I always assumed it was the tail whipping back and forth like a ribbon on a stick. If you move a ribbon on a stick fast enough it makes a noise and the pitch change was due to both the decreased viscosity as the temperature rises because as it falls the amount of oxygen feeding the flame increase and also due to the short tail length as material is burned up. Which was evident by the smoke trails which were also a zig zag pattern. Which loved watching rise into the air. Also, the best plastic for this was plastic grocery bags wound up on a stick and lit on fire. It was a must do every camp out growing up as a kid.
3:14 My thoughts here is that it has to do with how the material burns away as it falls, or how the flame comes off from the material as it falls. The stir rod burned away so fast that the sound was either to high pitched or didn’t have enough time to generate it (the drops barely reached the water if it did at all.) The nylon rope gets dropped with more material than the weaved sandwich bags, creating more surface for air resistance, slowing and lowering the pitch of the sound. Another reason using the same criteria would be the flame approaching the speed of sound, perhaps lifting the drop higher would produce a variation? More tests needed.
I remember that sound when I was a kid. I was in charge of burning trash in the burn barrel and would lift burning plastic milk bottles to watch them melt. I got the same sound from them.
I wish I had the answer, but I also can't believe you asked the question! Years ago, I had a fire in my backyard fire pit and one of the kids threw a large, clear, rolled up plastic bag into the fire. As it melted and smoked, sending soot into the air, I used a stick to try to remove it. When I picked it up, of course it started to drip and we (me and the kids) were fascinated by that exact sound as the drops of melted plastic fell to the ground. I always assumed it had something to do with wind resistance acting on the flame as it fell but I thought I'd need to film a flaming drop in slow motion as it fell to prove it. Inquiring minds want to know!
Hey. You talked too much and didn’t let us listen for the sound. Esp with the ones you said didn’t make sound … you know our ears lose hearing as we age. Also,shouldn’t you wear a mask when burning plastic. I testing experiment tho.
@@MoonberryJam93 Lolol. I appreciate the suggestion. I may be old, but I do in fact know to turn up the volume. It was thoughtful of you to chime in though, much love 💕🐝💕
@@amazinggrace5692Well you're generating thst type of response because what you said doesn't make sense when the sound is obviously clear multiple times. 🤷♂️🤷♀️🤷
@@MoonberryJam93 turn up the volume? Smart people in this screwed up world. By turning up the volume would be turning up the voice too and than we'd be in the same predicament, talking over the noise.
It Is The Same Effect You Get When Lighting A Lighter In The Wind. The Weight Of The Burning Material Pulls Downwards Causing An Updraft That Partially Extinguishes The Material In Free Fall Which Then Resonates To Cause The Whoosh/Whip Noise You Hear In This Experiment.
Sound is vibrations traveling through air. When materials are woven, there is a slight unwinding as it burns. The sound is likely the unwinding of the plastic as it burns. The fire creates a pocket of gas that helps amplify the volume.
What about when not woven? We used to do this simply my putting grocery bag loops on a stick and lighting. No weave. I feel like that may not be the primary cause, tho it's very likely it has an effect on the results.
It also happens on fast food straws. They're nice since they have the structure to hold themselves up like a wand (just make sure to put it out before you burn yourself)
When he was dropping them down the elevator shaft it appears that they may be rotating, not just vibrating - that that does match the sound, if they rapidly increase speed as they disintegrate.
I noticed the same thing as a kid repairing our skis with 'ptex'.... you have to burn it to and it drips into the damaged spots , where you smooth it an ready it for waxing.... but the ptex plastic would 'scream' as it dripped.
In the late 80's, when I was at school, our science teacher did this with a twisted-up plastic shopping bag [when they used to be a lot thicker plastic than today] suspended from up on the ceiling, into a bucket of water. It would make loud high pitch zipping sci-fi noises that we had never heard before or again since. This was close enough to what it sounded like.
i think a flame outside while the wind is blowing makes a similar sound. they tend to be larger flames, so i think the smaller the flame or the faster the speed of air resistance changes its pitch. those are just my initial thoughts, i may be wrong.
Accidentally discovered this sound while camping in the desert many years ago. Had a plastic milk carton on a stick and it caught on fire and started making these same noises.
I have found that twisted up plastic shopping bags, and tightly twisted lengths of heavy duty shrink wrap material work the best, for loud and consistent buzzes, anytime I've wanted to show this to friends or do sumthin weird around the campfire. The shrinkwrap around bundles of some gas station firewood would work... Otherwise would have to intentionally be brought on a camping trip most times, but a plastic shopping bag is almost always easy to come by.
Sounds a bit like the air compression and contraction speeds up. I imagine in slow mo we would see a ripple of flames getting faster as the mass accelerates towards the plate and causing a bit of doppler and reflections off the surroundings. Maybe it's combustioning and the extinguishing super fast over time?
There is sound to all material & some have trapped oxygen escaping as the burning fuel drips. If you had mics that could follow each drop, the sound would be erratic pops with a consistent tone. What's being heard is the Doppler effect as it falls away from the ear and the mic. You can create a similar effect with an uptrght bass. Tap a string with a sharpened pencil lead at one end and travels to the opposite.
So, as an artist I have melted and warped plastic for a variety of things, I think black plastic bags were the coolest. That being said, I stopped doing it because I was worried about ventilation and what this might be doing to my own, or my housemate's lungs, and was eventually asked to stop even doing it outside. I have to wonder though, which plastics are relatively harmless to melt and which ones should be heavily avoided without a full respirator and goggles. I haven't the slightest clue what to even start looking for with this. Sidenote. I use to be a cashier and noticed the sheer megatons of plastic cores of reciept tape rolls that would get tossed daily. I tried doing something with them creative but had an extremely hard time joining them together and gave up trying. I don't know what kind of plastic those things are even made of but I almost wonder if they are mixed with some sort of heat resistant material. Super glue doesn't work, hot glue barely sticks, and epoxy does but is expensive/time consuming. The last successful use was bathroom tile caulk which eventually warped too much under heat over time and fell off. I feel almost a civic duty to figure out how to recycle these but I am stumped.
We used to use garbage bags. I’m glad I saw this and someone finally addressed this noise. I’ve always equated the noise to be liquifying plastic sizzling on its way down. The higher the drop the more intense the zip is. I always wondered if it was because it gathered speed from higher distances.
If you take an empty bread bag and tie knots in it at two to three inch intervals hang that bag up and light the bottom of the bag ablaze it will make these noises. But the difference is that when it gets to the knots it starts making a high- pitched streaming sound. In between the knots it returns to a more of a lower tone.
I discovered this effect with polystyrene foam. the zip sound was a bit higher if i recall. this was in the 90s and i find it fascinating that curiosities align through the ages. i can not believe that someone else had the same exact experience and thoughts as me and came to the same conclusions as well. quite interesting indeed.
I'm also a child of the 60s. We spent summers in the country helping out on relative's farms. There was no trash pickup, so we had fun burning the trash. A few types of plastic made this vooop sound, but the loudest and most fun were the white plastic bleach bottles. We fought over those. They were much louder than I'm hearing here, and similar to the sounds at the end from the elevator shaft. I don't know what caused it , but the light does pulse.
It's the speed at which different densities of plastic drip... so, when the plastic is braided and loose, a glob of fire can burn the strands that support it, setting itself free (the glob of fire) so that when it falls through the air, there is still enough fuel (in the glob of fire) to react with the air rushing past, which makes for a livelier flame, and that lovely noise. This sound effect will work with any plastic that has the right speed and density drip.
"ive my love beats on from 1964 when i had hair down to my shoulders and was a love child" haha such a wholesome and cute old man, instant liked the video :D
I think this is similar to the mechanism of a Reijke tube (sp?), minus the resonance. It has to be burning pretty hot to work, which I think is why some didn't work. So it heats up the cold air in front of it, that air expands, it moves through that air, hits cold air, repeat. This causes pulses of air expansion. The frequency this process repeats is what we hear. I did this growing up, with plastic grocery bags and milk jugs on sticks. I called them torches, and was mesmerized by the sound they made.
I'm not a scientist by trade, only by heart, but the two confounding factors I'd first want to control for is the density of the plastics and the angle at which the fire droplet leaves the rod. If possible, melt at lower temperatures into uniform size rods, then run each burn experiment while it's held at a certain angle from a static stand. I'd also measure the temperature at which each plastic burns. The ropes were closer to vertical than the rods, therefore experiencing the effect of rising flame along a vertical fuel source- pre heating the fuel, so also the rate of ignition (if it works the same in ropes as bush fires). This could affect the rate the droplets leave the source and the overall heat of the droplets.
I found this same strange noise back when we would steal the neighbor's plastic sticks used for growing vines and then burn them. I say this now as I was about 10 years old and this was about 40 years ago we I did this. I am glad to see that I did not imagined this and closes a chapter in my life of some unexplained things.
We used to do this with twin lead TV antenna wire when I was a kid. I still remember the sound. I have a "Danger Club" for my grandkids and we do all kinds of projects that kids are normally sheltered from these days. Great fun!
personally i think that because of the air rushing into the burning plastic as it's falling is feeding the flame and making the sound we hear, also this would. account for the enhanced sound from it falling from a higher point. Subscribed, i am happy your channel popped up in my feed.
Wow, first video I've ever come across that addresses this. We did this in the far back area of a neighborhood friend's property back in the '70s, but with furniture foam. They had a junk pile back there with old furniture. We'd hold up a piece of the foam from the padding and light the corner. It would produce that same sound when it started dripping.
Oh my does this bring back some memories. As young kids, my dad had a pile of wood covered in black plastic sheeting. My older brother discovered this sound by melting the edge with a burning stick. This was so neat and fun, so I grabbed my own stick and was having so much fun till it started to catch fire. My brother ran to the house and came back with a cup of water and by that time it was three feet high. We'll that stack of wood went up like tinder. I ran and hid....the whole day! I thought my Dad would skin me alive. They called and called but I would not come out for like 8 hours. Come to find out my dad had meticulously torn down an old Victorian house and had all the ornate trim work under that tarp so he could put it in our house he was building. It represented a whole summer of part time work. Always felt bad about that.
It probably happens with the with the less dense plastic because as the plastic is falling it is cooling off generating the crackling sound. Like when wind blows on a fire it makes a similar sound. You can blow on a candle just right and make it make a fwump sound similar to the sound here. The shape of the plastic as it falls would probably contribute too because I am thinking that since plastic bubbles-up as it burns, the less dense plastic is bubbling as it is falling and the size of the bubbles in the plastic are what allow there to be an audible pitch.
I knew right away what that sound was going to be. Back in 1974, I was burning trash and of course playing around with a stick in it plus stirring it up to burn better. A one gallon plastic jug was trying to fall off to the ground so I put the stick through the handle to lift it back to center of the trash. As I lifted, the heat had started to melt it and I twirled the molten plastic around the stick then saw it drip down about 3 inches and thought I heard something faint so I let it drip to the ground. Wow, it really started singing then. I did this again and again everytime I burned trash until they banned burning in barrels. Those gallon jugs work really well.
My friends & I stumbled across this when we're were kids, way back in the 70s. We were walking down the bank of a river, and saw an empty Prestone bottle hanging from a tree limb. Don't know why it was there, but we lit it on fire. The plastic dropped about 7 or 8 feet, and made the coolest sound, lol.
When I was a lot younger, I used plastic flowers that had a plastic-coated wire stem. They almost had a whistling sound when dripping from the stem. Very much worth a try.
The woven plastic deforms while heating, releasing tension from winding, rapidly exanding the surface area, and combustible/accelerant volumes. It may continue the unwinding spin aswell, creating more encouragement to increase the surface. Sound is the acceleration of the spin, and rapid combustion
We lit a folding top igloo cooler on fire while taking 2 hits of acid and the sound is amazing. Did this back in 2001 and this is the first time I've heard someone else talk about it.
My theories: 1.) maybe the drop has some sort of fan shape because of the weave, and spins through the air as it falls? 2.) The drop breaks down slightly into other oil based compounds, and that slight breakdown combusts as it falls? 🤷🏽♂️ IDK
Its the sound of the Leidenfrost effect. The sound made by water hitting and extremely hot surface is the same sound, accomodating for the difference in materials. The heated body creates a boundary layer that doesnt allow the fluid to directly contact the heated body. In this case theres likely a pulsed oxidization effect, where the leidenfrost layer only allows oxygen to reach the superheated and anoxic fuel vapor in bursts, magnifying the sound created by the expansion pulsing
I know the cause. Have you ever noticed a candle makes the same noise if you lightly blow on it so it almost goes out, but not quite? What I believe to be happening with the looser plastics is the flame is getting close to extinguishing from the air movement like the candle and the denser ones have a much more stable flame due to the material having to heat up more to form a drop and the density of the drop would further increase the flame stability. Furthermore I believe the sound, both in a candle and in this loosely packed plastic rope, to be caused by the flame displacing air like a small explosion caused by the vapor trail igniting behind it as it is being partially extinguished as it falls.
I loved to do this as a kid! We had so much fun with this. My guess is it's the gas reigniting on the way down. The frequency of the sound will probably corelate with the amount of reignitions per second. The molten blob falls down, and as the gas is what's burning, the faster the blob falls, the more the flame 'lags' behind. At one point the flame and blob get separated but the flame still has enough power and the blob is still emitting enough gas to allow the flame to climb further down to ignite the gas again. This happens in quick succession and creates the sound. The frequency should be related to the amount of ignitions per second. This is my best guess.
Plastic medicine/vitamin bottles can also make the sound, but only the opaque white ones, the clear ones don't make the noises as often or as loud, but if you melt the white ones onto a stick and hold it about 4-5 feet off the ground those things are incredibly loud, like loud enough you can hear them from 20-30 feet away.
I think, what we are hearing is air, heated, passing through gaps in the burning medium. We certainly hear the effect of air pass the flame, when you burned two types of plastic the tone was different, the holes were different. That is what I think, I would try with several types of rope & material! 👍🏿👍🏽👍🏻🥸
I think the less dense plastic is able to make a larger globule of molten plastic and it is the molten state of the plastic that is vibrating as it falls. This explains why the sound gets clearer as you raise the plastic and why the denser plastic makes a small globule and produces no detectable sound (though I suspect it is there at some higher frequency that we can't readily hear).
This is amazing, only last week I discovered the same effect,, me and some friends were sat under a tree, the tree has some kind of heavy duty rope tied up in it as a swing but it's restricting the tree and we tried to burn the rope away, I tried to start the rope burning by using a sandwich bad to get it burning, it failed to ignite the thicker rope but made that sound, I was mesmerized! The sound doesn't start until the burning material has fallen for 5/6 foot, I think the fireballs have to reach a certain speed,, and I think it could be that the reaction moves into new oxygen and reignites ,, like a pulse jet effect,,, I really glad to see somebody else have interest in this! I didn't search for videos about this, just popped up on my feed,, thanks AI 😁, I have of course subscribed,, thank you!
Flammability of material + the rate of oxygen consumption = pitch; temperature of burning material = amplitude, simplified. As the material burns and falls through the air it causes the fire to oscillate as the aerodynamics causes a vacuum behind the droplet, depending on the material's flammability and the rate of oxygen consumption, can make a field of oscillating plasma (and therefore sound based on gas expansion and turbulence) behind the droplet. On the note about surface viscosity, depending on how thick the liquid is can determine the aerodynamic cross section of the droplet, (which if balanced with the right conditions like turbulence mixed with fuel burning resulting in getting more air to "flare" or "flicker") which can be used to determine the apex of burning (where the burning material releases the most energy) to make it louder and even change tonal qualities.
In high school, 45 or so years ago, a friend of mine and I found that the McDonalds straws (at the time anyway) would make a sound like your first example but it seemed louder than what you're using but perhaps that's just how it's mic'd . Give those a shot. I thought maybe the hollow straws amplified the sound in some way. Thanks for sparking the nostalgia and the curiosity!
Its the turbulence from falling. Like blowing on a campfire it has that woosh sound. But it keeps whipping through the air oscillating the burning pattern. And my guess about the acrylic not making the same sound is something along the lines of more of a liquid consistency creating a more streamlined drop without as much turbulence whipping around the flame. Different shearing of air/flames because of different consistency plastic melt.
In my past as a 10yo researcher I found that plastic /nylon zip ties worked well for this. Note to head the advice for the screwdriver/lamp reflector for PPE. ~40 year old 2nd and 3rd burns leave marks.
Well as the flame move through the air, it would increase the relative pressure around the flame, since heated gases tend to spread out more.. and then if something were to cause the flame to fall with an oscillating velocity that would create a sound.. although I guess that would be true even without the fire as any falling object is going to be causing small changes in pressure around it.. but I would think the flame would amplify that.. perhaps tiny jets of material are causing an upward force.. or possibly a downward force, I would think as the flame moved into an area of higher pressure it would increase the burn rate. Pressure would be effected by both the heat from the flame and the velocity. Maybe there is a feedback loop there
Droplets can oscillate as they fall and this is caused by a combination of gravity, wind resistance and surface tension. A burning droplet displaces air which creates a small noise. The air rushing past acts like a blower on a forge which creates a rumble. Lastly the combustion creates expanding hot gas and that probably creates more convection than burning in place because of that blower effect. All of those things, including the oscillation of the droplet probably contribute. I'm not sure about the vortex shedding of the droplet, rain is usually pretty quiet until you start hearing the drops splashing on the ground.
as the flame falls, it intakes air stoking the fire, which forces flame upwards. a non-porous plastic such as a solid stick doesn't have spaces for the air to go through, so instead it goes around the droplet. in a fibrous plastic however the air and flames can pass through the fibres, which generates a sound. you don't even need a flame to see this - since the only purpose of the flame is to force air through the material, the same effect can be achieved by swinging a rope or stick in a circle. a solid stick will not generate a sound at the same speed that a fibrous rope will begin to, and the rope will generate a lower frequency sound than a stick.
I think what your referring to we once called a "zilch" which was made from twisted plastic dry cleaner bags . You'll find the sound you seek there if the bags are the same . The noise it makes is really a rush .
Particle density, surface area, air flow. It’s a lot of mild explosions as it is diffuse when falling through the air. Have it drop farther and test the sound at different altitude as it falls, maybe two or three stories. Plastic isn’t the only substance that will do that. Also thinking “wind shear” stuff.
my hypothesis is that there is a tiny amount of air, in the braid of the rope, that when it is burning upward it is trapping a bubble in plastic, as the fiery blob falls off, it immediately begins to cool and simultaneously contracts slightly. this action forces the tiny bubble to move toward the most molten spot on the blob and ejects the trapped gas. the oreffice that is created to allow the gas to escape is also cooling and begins to change shape, thereby also changing the tone. but some of the way it sounds is probably due to the Doppler Effect. just my hypothesis y'all. that could also explain why the more dense plastic did not make noise as it fell. no air trapped in-between the fibers as it melts.
Medium burns and gases move into fire. Accelaration increases rate of gas intake to fire, creating turbulent disruption to super heated gas. Its popping the barrier between pressure zones at rates approximating the rate of fall. It's the fire equivalent to bubble pops but quicker. You'll hear similar sounds from wind through fire and waving a fire torch.
You can also use a plastic grocery bag. Roll up the bag so that you end up with two handles at one end and the bottom of the bag on the other end. Next you tie a tight knot every 2 inches along the bags length. Tie the handles to (we used an old wire hanger) something fire proof then light that bottom knot. Not only will you get the strange zipping same with each flame that drops but each flame will be blue when it drops. We called these “Flaming Blue Groovies”. They make great tracers if you turn out the lights at night before lighting one.
I'm not an expert or anything but I think it could have something to do with the sound made when you blow on a candle. You can hear it in the video too. If you blow on the candle hard enough, it will go out, but it's just the plastic falling through the air. Maybe it's the friction against the air around the fire and the different plastics have different sized drops which is what changes the tone and whether you can hear it.
I already knew this noise, we used to melt lead scrap from a printing process, that cme to us with a kind of tarry substance on it. If you put it all into the furnace with the tar on it, the furnace ran too cool. So one of my jobs was to prop the pieces up on a ledge, then walk back and forth with a big blow-torch, the trick was to get it just hot enough to run off, but not hot enough to burn. And when it did start to burn, the drops, falling through the air, made exactly this same sound.
I was a bit of a pyromaniac in junior high (1986) and I had a toy plastic tower from when I was younger that had a bowl on top with a hole. You fill the bowl with water and it would drip down through different elements causing some things to spin, a little bucket thing would fill and tip once enough water was in it. Anyway I don't know what made me think to burn it but I did and it was making that same sound. I had not heard that sound up until I just watched this video. I think you need to go around gathering different plastics and provide more results, please.
Same thing happens in big bonfires when theres a rising flare up. Could be moisture in the air being pulled in, sizzling as the flame flares as it drops.
Brings me back to 1986. Bored teenage me on one of my brother's logging sites in the winter, hanging out waiting for him to get back with diesel for the skidder with a campfire going. Stuck a plastic jug on a stick and discovered this bit of sorcery.
Some phenomenon I know happen, and I'm pretty sure are factors, here -- Fire flutters. Anyone standing near a campfire or such when a wind picks up might recall a "fluff" that changes to a "floof" sound. Some polymer off-gases are flammable. It's generally not volatile enough to worry about, but may affect tonality. Fire creates its own wind. Where 2 or more wind currents come together, you may get a sound. A very hot thing moving through atmosphere can cause a thunder effect, like another commenter mentioned. Different temperatures of fire sound different. I'd try to get a thermograph on those flames. Braiding has room for air/O2. The solid stuff might burn hot, maybe really hot, but it doesn't have the air being superheated and expelled by the fire. Plus, the solid tubing was dripping almost like water from ice. I bet that smoother flow is a factor. Model sprue plastics are constantly changing. A couple of companies actually have their own proprietary formulas. And pretty much all of them are very different from the stuff my Uncle was building in the '70's.
It reminds me of how a candle flame becomes noisy when you blow on it. In candle flames this is caused by uneven heating of the air producing miniature explosions / thunderclaps because in some moments the wind disrupts the burning while in other moments it actually makes the burning more efficient. The mixing of flammable gas is turbulent in the wind, hence the uneven burning and the noisy sound. I think that's exactly what's happening here, and the fact that some materials produce this effect while others don't, and that different baseline frequencies occur in different materials, probably has something to do with the intensity or integrity of the burning process versus the the disruptive intensity of the burning mixture falling through the air. The latter is constant between materials (same atmosphere, same gravity) so it obviously has to be something to do with the material itself. If the intensity of the burning is consistently stronger than the intensity of falling through the air then I hypothesize the noise won't occur.
I used to do the same when I was a kid. With my friend we often lit campfire close to a river and one day there was a water plastic bottle, Evian if my memory is correct, and i put it in the fire with a stick to see if it would burn or melt first. And when I removed it, it was doing both at the same time wich fascinated me, and I remenber the strange noise it was doing really similar to this one (I remember a higer pitch than in the video but maybe it's an effect of the mic) and the pitch was going higer as you would drop it from higer. And what I supposed at the time was that it was the vibrating drop of molten plastic on fire that was doing the noise by making some sort of fire wave as it was sort of pulsating through the fall giving as we can see in the video those of multiple spot of light wich are burst of flame. (I though that the fire was making the drop pulse but later learn that a falling water drop pulse the same).
When I was in late elementary/middle school, one of my chores was taking the trash out. We lived in the country, so most of our trash would be burnt. I noticed pretty quickly that milk jugs would make this sound when burning, so I'd spend half an hour burning different materials in the burn barrel. Got to hear a lot of these... and the occasional explosion from something pressurized... Lol...
Physicist here. My first thought is that it's thunder. The heat of the flame expands the air that it moves through, then as the air rushes back in, the air that was on one side collides with the air on the other side, then it recoils, then rushes back in, etc, resulting in a short-lived oscillating pressure wave... a sound wave!
It also explains why, as the flame gets smaller, the sound gets higher pitched. The frequency of this effect increases because it takes less time for the air to rush back in and create the oscillating effect that we hear as sound.
There are probably multiple things going on here, too, so other explanations are also gonna have a lot to do with it!
I was thinking a similar thought, but also that the molten plastic is spinning as it’s dropping, or at least it looked like it was, which could play into the core idea. The flame comes off the plastic asymmetrically which causes drag on the atmosphere around it and applies an small force on the plastic causing it to spin on its falling axis, the further it falls the faster it can spin causing the pitch to change the longer it falls. Maybe the other plastics that didn’t make a noise were too heavy and don’t allow this rotation to take effect? maybe they’ll take more effect at a higher distance? Great, now we have more questions and still no answer 🙈
Not bad, but it's almost definitely the flame front being pushed down from the front to the tail of the droplet with the gas and then recombusting as the gas rebuilds
then why wouldn't all types of plastic have the effect? is it the shape of the melting plastic that causes part of it?
@@beyondtheillusion333I think this is definitely a part of the effect, perhaps the fact that it was melted from stranded or thin plastic gets small air bubbles trapped inside and as they heat up they expand? Something with the volatiles in the molten plastic has to be a factor...
We used to do this as kids, but with milk jugs. You get a high pitch and a pretty blue flame.
The answer will be revealed through high speed footage.. It's time to call The Slow-Mo Guys..
I recorded the video through a high-speed camera and it was mostly just a still image that occasionally changed.
@@omegahaxors9-11 You should upload the video to your channel for us to see, whether you meant that you recorded your own high speed experiment or tried recording something playing the above video with a high speed camera like I assume you are trying to say, which would actually be just as interesting to see, honestly.🤔 *edited for clarification
@@Nine_Divines I recorded the video on my screen.
High speed doesn't record sound
@@omegahaxors9-11 no shit, a 30/60 fps video has still images in high speed? who could've guessed!
You made a version of a thing called a "zilch". I saw the upscale version in the late 70's as a kid. The proper way to make one is to take any similar plastic, like a trash bag, pull the bag to make it as narrow as possible then tie knots it it a few inches apart. Hang it up somewhere about 3-4 feet (or more) off of the ground above a white plastic 5 gallon filled halfway with water. This is best when done at night. You get the "zilch" noise from the melting plastic falling and a small flash as it enters the bucket prior to extinguishment. The knots create a moment of rapid "zilching" since the knot is a concentrated area of plastic. The rippling sound (zilch) is the fluttering of the wind trying to put the flame out but the plastic is able to resist due to the heat at which it burns and turns to a liquid. The hot, burning liquid is slightly resistant to being blown out like a candle. There is a layer of the melted plastic around each droplet that in effect, boils. As I understand it, this was best used in outside events by older adults where the consumption of natural herbal remedies took place. As a kid, it looked and sounded cool.
That is the one I remember and how we did it.
G,day mate old Aussie Boomer here, way back when I had to ride a kangaroo to school I made a thing with the help of my mum called a pyrophone (60s) that weird old thing had a similar sound. Keep the weird alive old fellah and all the best to you and yours from Jedro the Grate
Nice man thanks for the hypothesis. If I’m even using that word correctly
Zilch bag all the way.
Zilch also means "Nothing. Nada. Zip. Zilch. Zero."
My 2 cents as a guy who researches fluid dynamics, when spheres or other bluff bodies go through a fluid (air) it causes vortex shedding which also causes acoustics at the same frequency as the shedding. The frequency of the shedding is described by the Strouhal number, which should stay constant if the shape of the body does not change. Strouhal# = freq*diameter/air velocity. My theory is that as the droplet falls, it causes this shedding and acoustic frequency that you hear. As the droplet accelerates and as the diameter decreases from the burning, the frequency must rise to maintain the Strouhal# causing the fwooiip (low to high freq). Non bluff bodies do not cause vortex shedding, so if it is too slender (perhaps in the case of a less viscous plastic) than it wont cause it, though with a flexible tail it gets more complicated. Not sure about those details, though I think usually the tail accelerations would take energy away from the acoustics unless some resonance is there.
Perhaps if the plastic is more flammable, it may burn the tail before it can become a slender body, or simply makes it smaller and thus reduces the acoustic dampening it probably causes?
Or if the droplets start too small and generate only high freq noise, since most of its energy is in the frequency rather than the amplitude we can't hear it?
I also assume the fire has some affect on amplifying or facilitating the sound, because I don't hear this for rain or other things. Heat increases the speed of sound, so perhaps any sounds created in the flame get compressed together at its edge as they hit a slower medium and thus increase the amplitude of the acoustics?
So, to possibly measure the temperature of the falling drop would help to discover more needed information for that last stated case? 🤔
@@randolphfriend8260 I guess any more info would be nice but just knowing that the flame is extremely hot compared to its surroundings is probably good enough to know on that idea (though maybe the ratio of temp could give you an idea on the internal shedding freq to audible freq ratio assuming this ideas holds water?). I'd be more interested in how the flame and droplet move around while falling to create the sound waves.
bingo bango. I think you've got it.
@@randolphfriend8260 looking at the scar on the back of my hand from one of these melty torpedoes 40 years ago or so I can attest that its pretty dang hot! the shape of the scar is tear drop so it had a tail. I remember getting splattered as it went by so it most likely was boiling as well.
There's an old singing exercise using candle flame to learn control of your diaphragm. You light the candle, and try to almost blow it out, but without actually blowing it out completely. When you get it right, it makes a very similar sound to this, fluttering and sputtering. And you can see the movement of the flame and smoke coming off of it. It looks a lot like slow motion video that I've seen of various wind instruments like flutes, recorders, and whistles. When the light is right, you can even see the vortices in the smoke blowing away from you.
THAAAAANK YOU for doing a video on something you dont understand and admitting that you have no idea and want to know. People seem to think that a scientist needs to know literally everything and has no room to learn or grow. We all know so little. Its nice to see scientists saying "yeah i have no freaking clue. All i can do is speculate." While showing pure, unadulterated fascination with their lack of answers. Thats what science is ABOUT is being fascinated by unknowns and trying to find answers, not automatically knowing everything somehow.
We call this "Zippers"! Its caused by shedding "Vortex rings" of vapor of one side and then the other.
The size if the vortexes is relatively constant. However, as the drop accelerates in speed due to gravity
the frequency, naturally, increases. Hence the Zipping sound.
redrok
My thoughts exactly. Also... I notice even visually the flame has a ripple in it... like a flag in the wind. It whips back and forth. If viewed in slow motion I am willing to bet that the frequency of the ripple matches the frequency of the pitch of the sound. As the "wind" speed increases (speed it is falling) it increases ripple frequency. In fact I would put good money on that bet ;) *Side note... I have even heard and observed this same thing from a candle in a room with very still air. The updraft will cause this same effect and produce this same rippling and a similar sound. I came to all these conclusions way way back then in my younger days lol
Zippers! Melt an empty milk jug onto a stick and light it up. Pyro fun. And I have a burn scar on my hand to remember 30yrs later.
@@raw760 I used a plastic bottle and got a 3rd degree small burn on my leg has a guts of wind push it in the wrong trajectory hopefully the drop was small but still the pain made me never do it again. And I clearly remember this strange noise it was making.
i used to burn the end of a plastic knife and drip it on my arm to freak ppl out (i was that idiot). It would burn perfectly round circles thru the top layers of skin leaving only a completely white hole - but no pain at all (must have got all the nerves?) Now i have a dozen small circle scars on my arm that i have to explain to my kids :/ Dont try at home
Isn't the plural of "Vortex" actually "Vortices" ? English is weird.
Found this sound when I was a child and we needed to start a campfire while very wet. We lit a plastic milk jug and as it dripped it made that distinct sound. The plastic was able to light the campfire and we stayed off hypothermia and learned that cool noise.
Milk Jug Farts (from high school bonfires)!
As a boy in the '60s who played without benefit of adult supervision, I too discovered the unusual "vvvvvVT !" sound from the drips of burning plastic milk jugs.
This takes me back. At the campfire, as a kid, I'd take an empty foil topped sugar water container (those bright colored drinks your mother buys because it seems healthier than pop) and light it in the fire.on the end of a stick. Then you get the 'vvvvvt' sound when you hold the stick and let the molten plastic drip.
People should send this video to Steve Mould, he'd love it
He would call it the Mould effect
@@zach3826 yea hes a pathetic loser that needs a real job
Throwing a lit match can sometimes create an interesting and surprisingly loud sound.
Well now I have to try this.
Like striking it and throwing it immediately? or when it's already lit and then throw it?
I used to put " Blue tip " brand strike anywhere matches in my BB gun and fire it into a solid nearby. No bb, just the match. Almost everytime, the match exploded like a firecracker. Of course, if you fire from more than about 2 or 3 feet, it would tumble and not strike with the tip. I never see these matches anymore. I guess for a safer match, they made them only strike on the box. I used to buy the 750 match boxes in 3 packs. Cheap entertainment. Also at night, I placed a flat rock at end of barrel with a very slight tilt. The match would strike this stone on its way to the sky, like a cheap fireworks. You must be careful where you do this. That match may still be lit when it lands and the winds could carry it a ways. In fact, I had one that failed to light after firing and a few seconds later I see it light when it landed on a neighbors shingle roof and tumble to the ground and light some leaves. I ran down the alley and stomped it out. That was about the time I stopped doing this trick. lol
I did it as a kid. That was fun
in my opinion this is the same phenomenon that happens when you try to blow out a fire that just refuses to extinguish. there has to be a partial or complete extinction of the flame and a rapid reignition of the volatile gasses by sheer temperature (keeping in mind the plastic itself isnt burning, rather it is the volatile compounds that get released by heat). the ignition will make a small "poof", and the repetition of this on and off cycle will make a longer sound with a frequency that correlates with how fast it is happening. this will put size, type of plastic, etc. into the equation
That was my thought, that it might be similar the the buffeting whoosh or roar a flame makes when you vlow on it, but the pitch is much higher when the fuel source is smaller and the flame can oscillate faster.
But that doesn't resolve the mystery about why some plastics don't make the sound. I wonder if dropping the denser plastics from a greater height might get something out of them...
@@cliftut It's a function of the surface area of the falling material. The denser materials all create finer drops which exposes a smaller burning surface area to wind buffeting. All of the less dense burning mediums produce larger droplets, which means more surface area to burn, which means more flames that are resisting the extinguishing force of the wind speed.
If you've ever blown on a campfire or candle, it's literally just the distorted sound that fire makes when you're blowing on it. As the drop accelerates, the pitch of the distorted sound increases with the falling speed of the drop because the frequency of the distortion increases relative to the wind velocity. So the rising 'zip' sound is caused by the acceleration.
I think you're on to something here. It makes most sense
When my house was burning, I was going down the steps. Just before I put my hand on the rail. A drop of burning plastic fell on it. I then put my hand right on it! Not leaving it long! My hand on fire, I try putting it out on my jeans. Luckily it was only a half dollar size flaming ball of plastic! Most of it went between my fingers! Seeing that brings back memories!! When the blister popped, I had a huge hole in my hand, compared to the area. It had to be a 3rd degree burn. I can still see the scars, looks nothing like the burn, it was mostly deep than wide, and being between fingers. make it seem smaller! Careful and Good Day!
I had to pause the video at the beginning to comment. Back in 1964, when I was about 7, I was a Hot Wheels freak. Remember those little cars that you would roll down the orange strips of track that snapped (slid) together? Well, I discovered that if you light one end on fire and let it drip it made the most amazing and awesome sound that I have heard to date! I couldn't stop! I ended up with no track...only a bunch of cars left. I WILL NEVER FORGET THAT SOUND! I even climbed on the roof so it would last longer...then a tall tree...the sound lasted for quite a fall and increased in pitch as it fell.
Thanks for the trip down memory lane!!
--dAlE
@joeroscoe3708SAME HERE! My mom was in tears. I was crushing them all for a monster truck show.
I first heard this sound back in the '80s. All of the neighborhood kids hung out in the woods behind the houses. There was a sand track back there where they would ride dirt bikes. That's how it got it's name, The Sand Pit, or The Pits for short.
We would occasionally have campfires out there. One day while I was roaming around by myself, I started burning random things, as kids do. When I got to an empty milk jug, that's when I heard this amazing sound. I have never heard it again until today, but that little zip, zip, zip sound always stuck with me.
Speaking of sand, it makes a similar sound when you walk barefooted on the beach. But yeah, as kids we would light bags on fire and marvel over the sound it made when it dropped. Ah, the simpler times.
we used to do this with milk jugs. dont remember is the opaque jugs worked, but the cloudy/almost see-through jugs made a great example of that sound.
One material which makes a great example of that sound is the plastic ring structure used to hold together six-packs of cans. I don't know what mechanism is making the sound, but as the drop accellerates downward it makes the sound go higher in pitch. I imagine that the moving air makes combustion more difficult, so you get a small buildup of unburnt gasses. Then when enough of the vaporised plastic has built up, you get a small flare of flame. The zipping sound is a series of ignition flares, which grow faster as the air speed around the drop increases.
Used to do this as a kid. Burned myself several times. The molten plastic would remain stuck to your skin for a couple of weeks. My favorite material was that stuff they bind cardboard boxes with. They look like thin flat belts and come in many colors. They also make mini explosions when they hit the water.
Cool! My first thought is get a hold of either Destin of Smarter Every Day, or the Slo Mo Guys, and record those drops in slo-mo!
My theory is that the sound happens because the falling effectively creates a powerful updraft and the heat/pressure differential from the fire on the drop could fuel a vortex with the right conditions. Essentially, the falling drop creates a vortex that gets tighter and faster until it collapses or the drop evaporates.
Hm. But then…any thoughts on how that would relate to the difference between the more- and less-dense plastics?
My guess is, because of the looser composition and different properties of the polymer chains that make up the plastic, some burn faster than others. In the case of nylon or styrene, they burn fast, so as the drops fall, the top of the flame at any discreet moment is unsustainable and its density is closer to that if the ambient air. In a visual sense, the top of the flame is "thinner" than the bottom, like mousse vs pudding. Because it has less influence on the surrounding air, the eddy currents produced by the mass of the flame below can whip the tip of the flame back and forth, producing sound.
The faster the meduum burns up, the less matter will be feeding to the top of the flame, making it weaker (less massive) and more able to be pushed by the eddy currents due. Because the lower mass allowes for faster acceleration, faster burning mediums will produce a higher pitch die to the faster motion of the flame tip. The slower burning the plastic is, the lower the pitch will be. This is why the very flammable styrene made a (guess) 300hz buzz, ehile the nylon, a slower burning medium, made a 60hz buzz. If dropped from a high enough place, the acrylic and hard plastic will also produce a sound, just lower than we can hear at first. As they burn up more fully at the bottom of the fall, they will also start to produce an audable sound. As they will have a more massive (amount of matter) flame to move as they drop, so the sound will start low and quickly "WOOOSH" up in pitch as the remaining plastic burns more fully and the flame becomes weaker.
A candle burns by using capillary action to feed the paraffin or oil to the wick, because there is a steady source of fuel, the flame stays strong. But when the fuel runs out, the flame gets weaker until it goes out. The weaker flame is less dense and will thus flicker more if the ambient air is disturbed. This is the same this that is happening as the plastic falls, it's using up the last of its fuel, but at different rates for the different plastics. The faster it loses mass, the higher the pitch becomes.
For a good visual idea of what's going on with the flame, Schlieren photography is a method of lighting that allows you to see the patterns of air and subsequent eddy currents around the flame. It also makes for a good demonstration.
en.wikipedia.org/wiki/Schlieren_photography?wprov=sfla1
sounds like a case for @SteveMould
Or Destin from Smarter Every Day
My random guess - the woven nature of the rope causes strands to stretch as the melted section detatches and falls. The strands vibrate in the air causing a sound. As they burn, they contract and the pitch increases (plus acceleration).
I think you're right. Anything related to just vortex shedding or flame dynamics doesn't explain why it only works with woven material. This could be tested by examining the drops left behind in the water. I think you're right about them getting shorter too, the pitch change seems to accelerate and they probably have a low terminal velocity anyway.
That's a sound I want to start hearing Sound Engineers use for all sorts of things. Like I can imagine mixing that sound into the mating call of some kind of fantasy frog or something.
as soon as i heard it i thought "i wonder if that's how they made the laser pew pews in star wars"
The VOIP! Found it a few years back taking a lighter to 6-pack rings. (For no good reason other than I'd drunk at least 6 sodapops.) I've tried to show friends its magic, but with only mixed success. I'm very happy to know others have heard the voip and wondered about its mysteries as I have.
We used to melt army men as kids. Made a really good sound about the same as the nylon rope. Think a high speed would show the glob of plastic oscillating. The ones that don’t make noise the glob is to dense and doesn’t oscillate.
4:59 It really feels like the falling solid bits feed extra air into the flame and it's just like blowing at a candle and bringing it to the point of nearly going out, simply fluttering in the "wind".
Different compositions would burn better and thus better keep the reaction going.
-edit: I think Steve Mould should be made aware, if he's not already on the case.
I used to do this as a kid with 5 mill clear poly plastic. The first time i discovered this sound i was enthralled.
I always assumed it was the tail whipping back and forth like a ribbon on a stick. If you move a ribbon on a stick fast enough it makes a noise and the pitch change was due to both the decreased viscosity as the temperature rises because as it falls the amount of oxygen feeding the flame increase and also due to the short tail length as material is burned up.
Which was evident by the smoke trails which were also a zig zag pattern. Which loved watching rise into the air.
Also, the best plastic for this was plastic grocery bags wound up on a stick and lit on fire. It was a must do every camp out growing up as a kid.
Everything is strange once the psychedelics kick in...
3:14 My thoughts here is that it has to do with how the material burns away as it falls, or how the flame comes off from the material as it falls.
The stir rod burned away so fast that the sound was either to high pitched or didn’t have enough time to generate it (the drops barely reached the water if it did at all.)
The nylon rope gets dropped with more material than the weaved sandwich bags, creating more surface for air resistance, slowing and lowering the pitch of the sound.
Another reason using the same criteria would be the flame approaching the speed of sound, perhaps lifting the drop higher would produce a variation?
More tests needed.
This man deserves more followers
I remember that sound when I was a kid. I was in charge of burning trash in the burn barrel and would lift burning plastic milk bottles to watch them melt. I got the same sound from them.
I wish I had the answer, but I also can't believe you asked the question! Years ago, I had a fire in my backyard fire pit and one of the kids threw a large, clear, rolled up plastic bag into the fire. As it melted and smoked, sending soot into the air, I used a stick to try to remove it. When I picked it up, of course it started to drip and we (me and the kids) were fascinated by that exact sound as the drops of melted plastic fell to the ground. I always assumed it had something to do with wind resistance acting on the flame as it fell but I thought I'd need to film a flaming drop in slow motion as it fell to prove it. Inquiring minds want to know!
Hey. You talked too much and didn’t let us listen for the sound. Esp with the ones you said didn’t make sound … you know our ears lose hearing as we age. Also,shouldn’t you wear a mask when burning plastic. I testing experiment tho.
3:00 you're welcome
I can hear it fine; maybe turn up the volume?
@@MoonberryJam93 Lolol. I appreciate the suggestion. I may be old, but I do in fact know to turn up the volume. It was thoughtful of you to chime in though, much love 💕🐝💕
@@amazinggrace5692Well you're generating thst type of response because what you said doesn't make sense when the sound is obviously clear multiple times.
🤷♂️🤷♀️🤷
@@MoonberryJam93 turn up the volume? Smart people in this screwed up world. By turning up the volume would be turning up the voice too and than we'd be in the same predicament, talking over the noise.
I remember doing this with a an old hula hoop as a kid in the 60’s.
It Is The Same Effect You Get When Lighting A Lighter In The Wind.
The Weight Of The Burning Material Pulls Downwards Causing An Updraft That Partially Extinguishes The Material In Free Fall Which Then Resonates To Cause The Whoosh/Whip Noise You Hear In This Experiment.
Sound is vibrations traveling through air. When materials are woven, there is a slight unwinding as it burns. The sound is likely the unwinding of the plastic as it burns. The fire creates a pocket of gas that helps amplify the volume.
What about when not woven? We used to do this simply my putting grocery bag loops on a stick and lighting. No weave. I feel like that may not be the primary cause, tho it's very likely it has an effect on the results.
It also happens on fast food straws. They're nice since they have the structure to hold themselves up like a wand (just make sure to put it out before you burn yourself)
When he was dropping them down the elevator shaft it appears that they may be rotating, not just vibrating - that that does match the sound, if they rapidly increase speed as they disintegrate.
Nope. Drinking straws will "zip"as well.
Nope.
I noticed the same thing as a kid repairing our skis with 'ptex'.... you have to burn it to and it drips into the damaged spots , where you smooth it an ready it for waxing.... but the ptex plastic would 'scream' as it dripped.
The zoned out look and reflection in your glasses at 3:15 made me laugh 😂😂cool video
In the late 80's, when I was at school, our science teacher did this with a twisted-up plastic shopping bag [when they used to be a lot thicker plastic than today] suspended from up on the ceiling, into a bucket of water. It would make loud high pitch zipping sci-fi noises that we had never heard before or again since. This was close enough to what it sounded like.
i think a flame outside while the wind is blowing makes a similar sound. they tend to be larger flames, so i think the smaller the flame or the faster the speed of air resistance changes its pitch. those are just my initial thoughts, i may be wrong.
This is my first time stumbling across your channel and I LOVE it lol thank you for doing what you do!!
Accidentally discovered this sound while camping in the desert many years ago. Had a plastic milk carton on a stick and it caught on fire and started making these same noises.
I have found that twisted up plastic shopping bags, and tightly twisted lengths of heavy duty shrink wrap material work the best, for loud and consistent buzzes, anytime I've wanted to show this to friends or do sumthin weird around the campfire.
The shrinkwrap around bundles of some gas station firewood would work... Otherwise would have to intentionally be brought on a camping trip most times, but a plastic shopping bag is almost always easy to come by.
Sounds a bit like the air compression and contraction speeds up. I imagine in slow mo we would see a ripple of flames getting faster as the mass accelerates towards the plate and causing a bit of doppler and reflections off the surroundings. Maybe it's combustioning and the extinguishing super fast over time?
There is sound to all material & some have trapped oxygen escaping as the burning fuel drips. If you had mics that could follow each drop, the sound would be erratic pops with a consistent tone. What's being heard is the Doppler effect as it falls away from the ear and the mic. You can create a similar effect with an uptrght bass. Tap a string with a sharpened pencil lead at one end and travels to the opposite.
So, as an artist I have melted and warped plastic for a variety of things, I think black plastic bags were the coolest. That being said, I stopped doing it because I was worried about ventilation and what this might be doing to my own, or my housemate's lungs, and was eventually asked to stop even doing it outside. I have to wonder though, which plastics are relatively harmless to melt and which ones should be heavily avoided without a full respirator and goggles. I haven't the slightest clue what to even start looking for with this.
Sidenote. I use to be a cashier and noticed the sheer megatons of plastic cores of reciept tape rolls that would get tossed daily. I tried doing something with them creative but had an extremely hard time joining them together and gave up trying. I don't know what kind of plastic those things are even made of but I almost wonder if they are mixed with some sort of heat resistant material. Super glue doesn't work, hot glue barely sticks, and epoxy does but is expensive/time consuming. The last successful use was bathroom tile caulk which eventually warped too much under heat over time and fell off. I feel almost a civic duty to figure out how to recycle these but I am stumped.
My pap always called this phenomena the zilch! We used to use the plastic soda can rings from 6 packs. What a blast from the past! Awesome work!
We used to use garbage bags. I’m glad I saw this and someone finally addressed this noise. I’ve always equated the noise to be liquifying plastic sizzling on its way down. The higher the drop the more intense the zip is. I always wondered if it was because it gathered speed from higher distances.
If you take an empty bread bag and tie knots in it at two to three inch intervals hang that bag up and light the bottom of the bag ablaze it will make these noises. But the difference is that when it gets to the knots it starts making a high- pitched streaming sound. In between the knots it returns to a more of a lower tone.
I discovered this effect with polystyrene foam. the zip sound was a bit higher if i recall. this was in the 90s and i find it fascinating that curiosities align through the ages. i can not believe that someone else had the same exact experience and thoughts as me and came to the same conclusions as well. quite interesting indeed.
I'm also a child of the 60s. We spent summers in the country helping out on relative's farms. There was no trash pickup, so we had fun burning the trash. A few types of plastic made this vooop sound, but the loudest and most fun were the white plastic bleach bottles. We fought over those. They were much louder than I'm hearing here, and similar to the sounds at the end from the elevator shaft.
I don't know what caused it , but the light does pulse.
I love that zip sound melting plastic makes, it's so awesome and some strings do that.... I'd do that and listen to it for as long as it lasted.
It's the speed at which different densities of plastic drip... so, when the plastic is braided and loose, a glob of fire can burn the strands that support it, setting itself free (the glob of fire) so that when it falls through the air, there is still enough fuel (in the glob of fire) to react with the air rushing past, which makes for a livelier flame, and that lovely noise. This sound effect will work with any plastic that has the right speed and density drip.
"ive my love beats on from 1964 when i had hair down to my shoulders and was a love child" haha such a wholesome and cute old man, instant liked the video :D
Its called reverberation.
Hot blast furnaces make a deep thumping sound caused by an harmonic imballance.
I think this is similar to the mechanism of a Reijke tube (sp?), minus the resonance. It has to be burning pretty hot to work, which I think is why some didn't work.
So it heats up the cold air in front of it, that air expands, it moves through that air, hits cold air, repeat. This causes pulses of air expansion. The frequency this process repeats is what we hear.
I did this growing up, with plastic grocery bags and milk jugs on sticks. I called them torches, and was mesmerized by the sound they made.
I'm not a scientist by trade, only by heart, but the two confounding factors I'd first want to control for is the density of the plastics and the angle at which the fire droplet leaves the rod. If possible, melt at lower temperatures into uniform size rods, then run each burn experiment while it's held at a certain angle from a static stand. I'd also measure the temperature at which each plastic burns. The ropes were closer to vertical than the rods, therefore experiencing the effect of rising flame along a vertical fuel source- pre heating the fuel, so also the rate of ignition (if it works the same in ropes as bush fires). This could affect the rate the droplets leave the source and the overall heat of the droplets.
I found this same strange noise back when we would steal the neighbor's plastic sticks used for growing vines and then burn them. I say this now as I was about 10 years old and this was about 40 years ago we I did this. I am glad to see that I did not imagined this and closes a chapter in my life of some unexplained things.
We used to do this with twin lead TV antenna wire when I was a kid. I still remember the sound. I have a "Danger Club" for my grandkids and we do all kinds of projects that kids are normally sheltered from these days. Great fun!
personally i think that because of the air rushing into the burning plastic as it's falling is feeding the flame and making the sound we hear, also this would. account for the enhanced sound from it falling from a higher point. Subscribed, i am happy your channel popped up in my feed.
Wow, first video I've ever come across that addresses this.
We did this in the far back area of a neighborhood friend's property back in the '70s, but with furniture foam. They had a junk pile back there with old furniture.
We'd hold up a piece of the foam from the padding and light the corner. It would produce that same sound when it started dripping.
Oh my does this bring back some memories. As young kids, my dad had a pile of wood covered in black plastic sheeting. My older brother discovered this sound by melting the edge with a burning stick. This was so neat and fun, so I grabbed my own stick and was having so much fun till it started to catch fire. My brother ran to the house and came back with a cup of water and by that time it was three feet high. We'll that stack of wood went up like tinder. I ran and hid....the whole day! I thought my Dad would skin me alive. They called and called but I would not come out for like 8 hours. Come to find out my dad had meticulously torn down an old Victorian house and had all the ornate trim work under that tarp so he could put it in our house he was building. It represented a whole summer of part time work. Always felt bad about that.
It probably happens with the with the less dense plastic because as the plastic is falling it is cooling off generating the crackling sound. Like when wind blows on a fire it makes a similar sound. You can blow on a candle just right and make it make a fwump sound similar to the sound here.
The shape of the plastic as it falls would probably contribute too because I am thinking that since plastic bubbles-up as it burns, the less dense plastic is bubbling as it is falling and the size of the bubbles in the plastic are what allow there to be an audible pitch.
I knew right away what that sound was going to be. Back in 1974, I was burning trash and of course playing around with a stick in it plus stirring it up to burn better. A one gallon plastic jug was trying to fall off to the ground so I put the stick through the handle to lift it back to center of the trash. As I lifted, the heat had started to melt it and I twirled the molten plastic around the stick then saw it drip down about 3 inches and thought I heard something faint so I let it drip to the ground. Wow, it really started singing then. I did this again and again everytime I burned trash until they banned burning in barrels. Those gallon jugs work really well.
My friends & I stumbled across this when we're were kids, way back in the 70s. We were walking down the bank of a river, and saw an empty Prestone bottle hanging from a tree limb. Don't know why it was there, but we lit it on fire. The plastic dropped about 7 or 8 feet, and made the coolest sound, lol.
When I was a lot younger, I used plastic flowers that had a plastic-coated wire stem. They almost had a whistling sound when dripping from the stem. Very much worth a try.
The woven plastic deforms while heating, releasing tension from winding, rapidly exanding the surface area, and combustible/accelerant volumes. It may continue the unwinding spin aswell, creating more encouragement to increase the surface.
Sound is the acceleration of the spin, and rapid combustion
We lit a folding top igloo cooler on fire while taking 2 hits of acid and the sound is amazing. Did this back in 2001 and this is the first time I've heard someone else talk about it.
My theories:
1.) maybe the drop has some sort of fan shape because of the weave, and spins through the air as it falls?
2.) The drop breaks down slightly into other oil based compounds, and that slight breakdown combusts as it falls?
🤷🏽♂️ IDK
Its the sound of the Leidenfrost effect. The sound made by water hitting and extremely hot surface is the same sound, accomodating for the difference in materials.
The heated body creates a boundary layer that doesnt allow the fluid to directly contact the heated body. In this case theres likely a pulsed oxidization effect, where the leidenfrost layer only allows oxygen to reach the superheated and anoxic fuel vapor in bursts, magnifying the sound created by the expansion pulsing
I know the cause. Have you ever noticed a candle makes the same noise if you lightly blow on it so it almost goes out, but not quite? What I believe to be happening with the looser plastics is the flame is getting close to extinguishing from the air movement like the candle and the denser ones have a much more stable flame due to the material having to heat up more to form a drop and the density of the drop would further increase the flame stability.
Furthermore I believe the sound, both in a candle and in this loosely packed plastic rope, to be caused by the flame displacing air like a small explosion caused by the vapor trail igniting behind it as it is being partially extinguished as it falls.
I loved to do this as a kid! We had so much fun with this. My guess is it's the gas reigniting on the way down. The frequency of the sound will probably corelate with the amount of reignitions per second. The molten blob falls down, and as the gas is what's burning, the faster the blob falls, the more the flame 'lags' behind. At one point the flame and blob get separated but the flame still has enough power and the blob is still emitting enough gas to allow the flame to climb further down to ignite the gas again. This happens in quick succession and creates the sound. The frequency should be related to the amount of ignitions per second. This is my best guess.
Plastic medicine/vitamin bottles can also make the sound, but only the opaque white ones, the clear ones don't make the noises as often or as loud, but if you melt the white ones onto a stick and hold it about 4-5 feet off the ground those things are incredibly loud, like loud enough you can hear them from 20-30 feet away.
I think, what we are hearing is air, heated, passing through gaps in the burning medium.
We certainly hear the effect of air pass the flame, when you burned two types of plastic the tone was different, the holes were different.
That is what I think, I would try with several types of rope & material!
👍🏿👍🏽👍🏻🥸
I think the less dense plastic is able to make a larger globule of molten plastic and it is the molten state of the plastic that is vibrating as it falls. This explains why the sound gets clearer as you raise the plastic and why the denser plastic makes a small globule and produces no detectable sound (though I suspect it is there at some higher frequency that we can't readily hear).
This is amazing, only last week I discovered the same effect,, me and some friends were sat under a tree, the tree has some kind of heavy duty rope tied up in it as a swing but it's restricting the tree and we tried to burn the rope away, I tried to start the rope burning by using a sandwich bad to get it burning, it failed to ignite the thicker rope but made that sound, I was mesmerized! The sound doesn't start until the burning material has fallen for 5/6 foot, I think the fireballs have to reach a certain speed,, and I think it could be that the reaction moves into new oxygen and reignites ,, like a pulse jet effect,,, I really glad to see somebody else have interest in this! I didn't search for videos about this, just popped up on my feed,, thanks AI 😁, I have of course subscribed,, thank you!
Never before have I felt the overwhelming urge to burn plastic... until now. Also, your safety device is fantastic
Flammability of material + the rate of oxygen consumption = pitch; temperature of burning material = amplitude, simplified.
As the material burns and falls through the air it causes the fire to oscillate as the aerodynamics causes a vacuum behind the droplet, depending on the material's flammability and the rate of oxygen consumption, can make a field of oscillating plasma (and therefore sound based on gas expansion and turbulence) behind the droplet.
On the note about surface viscosity, depending on how thick the liquid is can determine the aerodynamic cross section of the droplet, (which if balanced with the right conditions like turbulence mixed with fuel burning resulting in getting more air to "flare" or "flicker") which can be used to determine the apex of burning (where the burning material releases the most energy) to make it louder and even change tonal qualities.
I believe that you are hearing electrons in the atmosphere molecules rubbing against the molecules of plastic in some strange ways.
In high school, 45 or so years ago, a friend of mine and I found that the McDonalds straws (at the time anyway) would make a sound like your first example but it seemed louder than what you're using but perhaps that's just how it's mic'd . Give those a shot. I thought maybe the hollow straws amplified the sound in some way. Thanks for sparking the nostalgia and the curiosity!
Its the turbulence from falling. Like blowing on a campfire it has that woosh sound. But it keeps whipping through the air oscillating the burning pattern. And my guess about the acrylic not making the same sound is something along the lines of more of a liquid consistency creating a more streamlined drop without as much turbulence whipping around the flame. Different shearing of air/flames because of different consistency plastic melt.
In my past as a 10yo researcher I found that plastic /nylon zip ties worked well for this. Note to head the advice for the screwdriver/lamp reflector for PPE. ~40 year old 2nd and 3rd burns leave marks.
Well as the flame move through the air, it would increase the relative pressure around the flame, since heated gases tend to spread out more.. and then if something were to cause the flame to fall with an oscillating velocity that would create a sound.. although I guess that would be true even without the fire as any falling object is going to be causing small changes in pressure around it.. but I would think the flame would amplify that.. perhaps tiny jets of material are causing an upward force.. or possibly a downward force, I would think as the flame moved into an area of higher pressure it would increase the burn rate. Pressure would be effected by both the heat from the flame and the velocity. Maybe there is a feedback loop there
Droplets can oscillate as they fall and this is caused by a combination of gravity, wind resistance and surface tension.
A burning droplet displaces air which creates a small noise. The air rushing past acts like a blower on a forge which creates a rumble. Lastly the combustion creates expanding hot gas and that probably creates more convection than burning in place because of that blower effect.
All of those things, including the oscillation of the droplet probably contribute.
I'm not sure about the vortex shedding of the droplet, rain is usually pretty quiet until you start hearing the drops splashing on the ground.
as the flame falls, it intakes air stoking the fire, which forces flame upwards. a non-porous plastic such as a solid stick doesn't have spaces for the air to go through, so instead it goes around the droplet. in a fibrous plastic however the air and flames can pass through the fibres, which generates a sound. you don't even need a flame to see this - since the only purpose of the flame is to force air through the material, the same effect can be achieved by swinging a rope or stick in a circle. a solid stick will not generate a sound at the same speed that a fibrous rope will begin to, and the rope will generate a lower frequency sound than a stick.
I think what your referring to we once called a "zilch" which was made from twisted plastic dry cleaner bags . You'll find the sound you seek there if the bags are the same . The noise it makes is really a rush .
Particle density, surface area, air flow. It’s a lot of mild explosions as it is diffuse when falling through the air.
Have it drop farther and test the sound at different altitude as it falls, maybe two or three stories.
Plastic isn’t the only substance that will do that. Also thinking “wind shear” stuff.
my hypothesis is that there is a tiny amount of air, in the braid of the rope, that when it is burning upward it is trapping a bubble in plastic, as the fiery blob falls off, it immediately begins to cool and simultaneously contracts slightly. this action forces the tiny bubble to move toward the most molten spot on the blob and ejects the trapped gas. the oreffice that is created to allow the gas to escape is also cooling and begins to change shape, thereby also changing the tone. but some of the way it sounds is probably due to the Doppler Effect.
just my hypothesis y'all.
that could also explain why the more dense plastic did not make noise as it fell. no air trapped in-between the fibers as it melts.
It also works with the plastic that holds a 6 pack together! I did that all the time when I was a kid because it sounded so cool!
Medium burns and gases move into fire.
Accelaration increases rate of gas intake to fire, creating turbulent disruption to super heated gas.
Its popping the barrier between pressure zones at rates approximating the rate of fall. It's the fire equivalent to bubble pops but quicker. You'll hear similar sounds from wind through fire and waving a fire torch.
You can also use a plastic grocery bag. Roll up the bag so that you end up with two handles at one end and the bottom of the bag on the other end. Next you tie a tight knot every 2 inches along the bags length. Tie the handles to (we used an old wire hanger) something fire proof then light that bottom knot. Not only will you get the strange zipping same with each flame that drops but each flame will be blue when it drops. We called these “Flaming Blue Groovies”. They make great tracers if you turn out the lights at night before lighting one.
I'm not an expert or anything but I think it could have something to do with the sound made when you blow on a candle. You can hear it in the video too. If you blow on the candle hard enough, it will go out, but it's just the plastic falling through the air. Maybe it's the friction against the air around the fire and the different plastics have different sized drops which is what changes the tone and whether you can hear it.
I already knew this noise, we used to melt lead scrap from a printing process, that cme to us with a kind of tarry substance on it. If you put it all into the furnace with the tar on it, the furnace ran too cool. So one of my jobs was to prop the pieces up on a ledge, then walk back and forth with a big blow-torch, the trick was to get it just hot enough to run off, but not hot enough to burn.
And when it did start to burn, the drops, falling through the air, made exactly this same sound.
I was a bit of a pyromaniac in junior high (1986) and I had a toy plastic tower from when I was younger that had a bowl on top with a hole. You fill the bowl with water and it would drip down through different elements causing some things to spin, a little bucket thing would fill and tip once enough water was in it. Anyway I don't know what made me think to burn it but I did and it was making that same sound. I had not heard that sound up until I just watched this video. I think you need to go around gathering different plastics and provide more results, please.
Same thing happens in big bonfires when theres a rising flare up. Could be moisture in the air being pulled in, sizzling as the flame flares as it drops.
Brings me back to 1986. Bored teenage me on one of my brother's logging sites in the winter, hanging out waiting for him to get back with diesel for the skidder with a campfire going. Stuck a plastic jug on a stick and discovered this bit of sorcery.
Some phenomenon I know happen, and I'm pretty sure are factors, here --
Fire flutters. Anyone standing near a campfire or such when a wind picks up might recall a "fluff" that changes to a "floof" sound.
Some polymer off-gases are flammable. It's generally not volatile enough to worry about, but may affect tonality.
Fire creates its own wind. Where 2 or more wind currents come together, you may get a sound. A very hot thing moving through atmosphere can cause a thunder effect, like another commenter mentioned.
Different temperatures of fire sound different. I'd try to get a thermograph on those flames.
Braiding has room for air/O2. The solid stuff might burn hot, maybe really hot, but it doesn't have the air being superheated and expelled by the fire. Plus, the solid tubing was dripping almost like water from ice. I bet that smoother flow is a factor.
Model sprue plastics are constantly changing. A couple of companies actually have their own proprietary formulas. And pretty much all of them are very different from the stuff my Uncle was building in the '70's.
It reminds me of how a candle flame becomes noisy when you blow on it. In candle flames this is caused by uneven heating of the air producing miniature explosions / thunderclaps because in some moments the wind disrupts the burning while in other moments it actually makes the burning more efficient. The mixing of flammable gas is turbulent in the wind, hence the uneven burning and the noisy sound. I think that's exactly what's happening here, and the fact that some materials produce this effect while others don't, and that different baseline frequencies occur in different materials, probably has something to do with the intensity or integrity of the burning process versus the the disruptive intensity of the burning mixture falling through the air. The latter is constant between materials (same atmosphere, same gravity) so it obviously has to be something to do with the material itself. If the intensity of the burning is consistently stronger than the intensity of falling through the air then I hypothesize the noise won't occur.
I used to do the same when I was a kid. With my friend we often lit campfire close to a river and one day there was a water plastic bottle, Evian if my memory is correct, and i put it in the fire with a stick to see if it would burn or melt first. And when I removed it, it was doing both at the same time wich fascinated me, and I remenber the strange noise it was doing really similar to this one (I remember a higer pitch than in the video but maybe it's an effect of the mic) and the pitch was going higer as you would drop it from higer. And what I supposed at the time was that it was the vibrating drop of molten plastic on fire that was doing the noise by making some sort of fire wave as it was sort of pulsating through the fall giving as we can see in the video those of multiple spot of light wich are burst of flame. (I though that the fire was making the drop pulse but later learn that a falling water drop pulse the same).
When I was in late elementary/middle school, one of my chores was taking the trash out. We lived in the country, so most of our trash would be burnt.
I noticed pretty quickly that milk jugs would make this sound when burning, so I'd spend half an hour burning different materials in the burn barrel. Got to hear a lot of these... and the occasional explosion from something pressurized... Lol...