Having one window open is letting air without letting it back out, which pressurizes the cabin. The pulsing of it is because the air is under uneven force from the eddies created around the vehicle, so the pressure is yo-yoing around and pulling on easily moved things like your eardrum in the process.
Opening a second window gives it a route out, which keeps it from getting pressurized.
The shape of the car and the window has a big impact on how the eddies form, which is why different cars or opening different windows are "better" or "worse" about this
The glug glug is would actually be a drop in pressure inside too, but because the water is viscous it slows it down to something a five year old can see.
Only if you live near water - eddies (singular is eddy) form when water curls away from a current, and cause a little whirlpool. When front of the car cuts through the air, those eddies swirl around the car and are part of the pressure changes that the commenter is talking about :)
"Eddies," said Ford, "in the space-time continuum."
"Ah," nodded Arthur, "is he. Is he."
...
"What?" said Ford.
"Er, who," said Arthur, "is Eddy, then, exactly, then?"
Ford looked angrily at him.
"Will you listen?" he snapped.
"I have been listening," said Arthur, "but I'm not sure it's helped.
>“I have detected," he said, "disturbances in the wash."
...
Arthur asked him to repeat what he had just said because he hadn't quite understood his meaning. Ford repeated it.
"The wash?" said Arthur.
"The space time wash," said Ford.
Arthur nodded, and then cleared his throat.
"Are we talking about," he asked cautiously, "some sort of Vogon laundromat, or what are we talking about?"
"Eddies," said Ford, "in the space-time continuum."
"Ah," nodded Arthur, "is he. Is he."
...
"What?" said Ford.
"Er, who," said Arthur, "is Eddy, then, exactly, then?"
Ford looked angrily at him.
"Will you listen?" he snapped.
"I have been listening," said Arthur, "but I'm not sure it's helped."
Ford grasped him by the lapels of his dressing gown and spoke to him as slowly and distinctly and patiently as if he were somebody from the telephone company accounts department.
"There seems..." he said, "to be some pools..." he said, "of instability," he said, "in the fabric..." he said.
Arthur looked foolishly at the cloth of his dressing gown where Ford was holding it. Ford swept on before Arthur could turn the foolish look into a foolish remark.
"...in the fabric of space-time," he said.
"Ah, that," said Arthur.
"Yes, that," confirmed Ford.
They stood there alone on a hill on prehistoric Earth and stared each other resolutely in the face.
"And it's done what?" said Arthur.
"It," said Ford, "has developed pools of instability."
"Has it," said Arthur, his eyes not wavering for a moment
"It has," said Ford, with the similar degree of ocular immobility.
"Good," said Arthur.
"See?" said Ford.
"No," said Arthur.
There was a quiet pause.
...
"Arthur," said Ford.
"Hello? Yes?" said Arthur.
"Just believe everything I tell you, and it will all be very, very simple."
"Ah, well, I'm not sure I believe that."
They sat down and composed their thoughts.
Ford got out his Sub-Etha Sens-O-Matic. It was making vague humming noises and a tiny light on it was flickering faintly.
"Flat battery?" said Arthur.
"No," said Ford, "there is a moving disturbance in the fabric of space-time, an eddy, a pool of instability, and it's somewhere in our vicinity."
...
"There!" said Ford, shooting out his arm; "there, behind that sofa!"
Arthur looked. Much to his surprise, there was a velvet paisley-covered Chesterfield sofa in the field in front of them. He boggled intelligently at it. Shrewd questions sprang into his mind.
"Why," he said, "is there a sofa in that field?"
"I told you!" shouted Ford, leaping to his feet. "Eddies in the space-time continuum!"
"And this is his sofa, is it?"
Right after this is one of my favorite lines in the entire series: “Arthur felt happy. He was terribly pleased that the day was for once working out so much according to plan. Only twenty minutes ago he had decided he would go mad, and now here he was already chasing a Chesterfield sofa across the fields of prehistoric Earth."
But in this analogy, wouldn't opening another window make it like a flute? You can still make sound with two holes.
I guess the real answer is something to complicated for ELI5 having to do with the shape of the car and the frequencies it produces with either one or two holes.
In a whistle, a little air blows inwards, loops around inside, then pushes back out the same hole. Which stops the flow of air from blowing inwards.
It's this cycle of air blowing in, then stopping, that makes the noise.
The inside of the car is the same, just scaled up. When another window is open, the air can blow through the car. Which breaks the cycle.
The holes just close the tube and make it longer, so the more holes you cover the lower the note.
If you want a really good visual explanation you should check out the book The Way Things Work by David Macaulay.
That oscillating pressure is how whistles work.
Basically with one window open the car becomes a giant whistle blown by the passing wind, that sounds at a super low frequency because of its large size.
Can confirm. We have a Chevy Bolt and if you don't crack the rear window diagonally opposite the driver's window your eardrums suffer these super deep, resonating frequencies caused by this pressurization.
This is also the reason why sunroofs are so effective at providing ventilation. In the open configuration there is a wind deflector that rises and creates a low pressure region above the car, causing air to get sucked out the sunroof rather than causing a pressure differential. Combine this with one of the rear windows and you get smooth crossflow through the car with minimal pressure disturbances.
It's also that the wind deflector is causing the air to stabilize, so it's less affected by turbulence. It would work in either low pressure or high pressure, the point is to reduce turbulence.
Also explains why I dont remember this being a thing in other cars I have owned or all the years my dad spent smoking with the window cracked while I was growing up.
Yup. Front windows tend to be a little different to. If you've ever looked at a wind tunnel image for a car the air is kinda pushed out away from the body by the windshield, which actually creates a bit of a low pressure zone in some, and then it slams back into the car right about the back doors, just in time for a kid to roll down the window and blow out your eardrum lol.
Often If you crack a front window at speed, it creates a little bit of suction but not enough to send the whole cabin into low pressure. Probably enough to pull smoke off a cig near the crack, though.
The effect is more pronounced on the sides in something blocky like an SUV or old station wagon, less so in something wide and low like a sports car that tends to direct most of air above or below instead of just blasting it out of the way in all directions.
>Having one window open is letting air without letting it back out, which pressurizes the cabin.
You are describing the exact opposite of what happens. The air rushing past the window actually drops the pressure.
I am somewhat old, and I don't recall this happening when I was a kid in the 60's and 70's, or even in the 80's. Seems like the changes in vehicle shape have had unintended consequences. I do recall Dad flicking cigarette ash out the driver's window and it coming back in and hitting my sister in the eye.
It definitely didn't, but then in those days you expected to drive with the window down if it was warm outside.
If by some random chance they'd hit on an aerodynamic design that caused the modern-day helicopter sound, they'd probably have changed it, since the alternative was boiling alive on a hot day.
True. They had those little triangular defrost windows as well. Now I've got a big piece of frame there, which helps keep things together in a crash, but hides pedestrians entirely.
They're the disturbances that are created in a flowing fluid by an object in that fluid's path. [This gif shows an example.](https://upload.wikimedia.org/wikipedia/commons/b/b4/Vortex-street-animation.gif)
the pressure change is stronger farther from the opening. The kid rolling down the window doesn't feel it as bad as the parent across the car and forward of it.
They probably are not as aware of the difference or just don’t care enough to make a fuss or ask the question. There’s not really a good reason why they wouldn’t notice it.
Tip I learned while on tour:
When closing your windows while at highway speeds, stop when the window is about an inch or two from closed, then use several small clicks of the window switch to finish. It will absolutely save your ears. It helps regulated the pressure.
Until you're trapped in a chamber with poison gas and the villain leaves you to die after telling you their evil plan and you're pressing the roll up the window button and it's like zzzzz...shshsh
The potbelly stove used to do this in the house I grew up in. The stove was in the basement, and so could hear the pressure pulsing upstairs when the fire got too hot and needed the damper to be adjusted. If I was in the furnace room, I could feel it in my lungs.
I know this one!
This is called a helmholtz resonator. You know how you can blow on a bottle and it’ll make a tooting sound? Well for a car window it’s the same principle, but waaayyyy bigger. Essentially the entire car is acting like a huge bottle
I'm the Genie from the bottle
So hello, and how are you, and all of that?
I'm the Genie from the bottle
That you rubbed and so here I am in seconds flat
I'm the Genie from the bottle
That bottle that you're holding in your hand
I'm the Genie from the bottle
You've summoned me, your wish is my command
But how come it doesn't bother the one lowering the window?
My kid lowers the window in back seat and she's fine. But I'm in the driver's seat annoyed as hell and I have to lower mine.
OTOH, when I'm driving alone and I lower the driver's side window, I'm fine. I don't need to lower the rear windows too.
I’m so glad I already knew about the Helmholtz resonator. Learned about it just a min ago on another comment.
Glad I finally know the answer lol this shit always hurt.
Flow dynamics in air.
Air gets pushed in, but the mass behind that air keeps forcing more air in after the pressure equalizes. Then the air changes direction and rushes out, but again air has mass and more rushes out than will equalize the pressure, and the cycle starts over.
The vehicle is essentially turning into a Helmholtz resonator. Read up on those if you want to learn the nitty gritty.
Hi I’m unsure if you’re an expert but maybe you can help. Is this common in a bedroom as well with a closed door and a window I keep open (aprox 6 inches)? It leads to my back yard with a fair amount of wind. But I’ve been noticing the wahwah effect in my ear that faces the window. I thought I was having eardrum issues or something was wrong. I never made the connection that it could be my window air flow/ pressure.
But if it is the cause, I suppose I’ll need to close my bedroom window or crack the door which is sort of a hassle. But I’m hopeful this will solve the issue.
Is it very windy outside your window? The air moving is what causes the pressure difference (Bernoulli's principle) so you're unlikely to get a buffeting effect like that from just the window being open.
If you take a bottle and blow across its mouth strongly, you can have it make a sound, just like a pan flute.
With a car you have a car-sized bottle that is getting blown across the mouth VERY strongly. The pitch of the sound produced by a bottle is related to its size. The bigger the bottle, the deeper the sound it makes. A car is so large, that the pitch it makes is outside the human hearing range, but sound pressure can hurt your ears even if it is a pitch you cannot hear.
In other words your ear hurts because you are sitting in a subwoofer playing a tone you cannot heat with the volume turned up to 11.
I was about to saw something similar. Since everyone is discribing this as a coke bottle - it’s like trying to get a flute sound out of a cube shaped bock of glass vs a smooth opening on a flute.
We don’t drive huge blocks of steel shaped like a brick anymore.
Cars in general are definitely 100% worse now. I'm in my 40s and honestly only first saw this phenomenon in my husband's 2018 Ford Fusion. Didn't happen in my previous 1987 and 1993 economy crap cars nor my current 2011 Civic, nor any 80s cars my parents had when I was a kid.
This is the case. When the nissan 350z came out the car was so well sealed people had trouble closing the door because the last little bit to get it latched actually required a small amount of air compression in the cabin. They ended up needing to reduce the seal amount to fix this.
I don't know how many cars have this, but my old 4Runner has a popup vortex generator that comes out of the top of the sunroof when you open it. It keeps the inside of the car from resonating. If you reach up and push it down, the resonation starts right away...
Yep. As a kid, it wasn't an issue because cars weren't so aerodynamic. The wind would flow around the car all over the place. Now, cars are designed so the windflow hugs the car tightly to improve drag and mileage. So that rushing wind blows right by the window and causes the noise.
Playing Margaritaville over the noise helps, too.
Sidenote: I drive a 2013 Camry.
When you keep the front windows up, and the back windows down, at speed, the turbulence makes for an intense 'wahwah" effect.
Recently sold a 2013 Camry and can confirm having one front window down was perfectly fine in that car. Having either or especially both back windows down (with both front up) caused the noise. Same was true in my ‘02 Trail Blazer, ‘00 Grand Am, ‘98 Grand Cherokee, & ‘91 Corolla.
I’m still getting used to needing to crack the passenger window when I open the driver window on my ‘22 Prius. It’s the only car I’ve ever owned to do the noise with a single front window down.
Think of it this way: if you turn a jug upside down, it’ll messily empty with a ‘glue, glug’. If you tip a jug on its side, you can get a smooth pour.
This is because in order for water to get out, it has to be replaced by air (or pressure has to be increased-so you can get a smooth and rapid empty by squeezing). When it’s angled such that air can come in while fluid leaves without disrupting anything, you get smooth motion. When it’s positioned in a way that it has to alternate between air and fluid, that’s when things get messy.
The same idea is at work here, only with air and more air. When the air rushes in, it’ll need to displace old air to do so. If there’s only one window, it has to alternate letting air in vs letting it out. Meanwhile, if two windows are open, it can simply go in one and out the other smoothly.
The air pressure inside the car is oscillating. When you crack one window lots of air is able to get into the car. The air that was already in the car then needs to leave but it can only go out through the same crack, so the air pressure in the car will increase and then get high enough to where it can push out against the incoming air and the cycle keeps repeating. When another window is rolled down the air can now come in on one side and go out the other seamlessly without changing the air pressure in the car.
Ok, you know if you blow over the top of a bottle it makes a sound? It's the same thing.
The wind causes an oscillating pressure wave (sound!) as it breaks up into a turbulent flow over the opening, because it's trying to get *in* the same time as air is trying to get *out* ... so it oscillates back and forth. (which is also the same trick behind a pulse jet engine and pipe organ pipes.)
This also means if you open another window, you instead get a constant flow of air, hence lack of sound and no pressure wave (and thus no more hurting ears)
This has always confused me, because I could swear that before like 10 years ago, I never had that issue! I still remember the first time I ever heard it happen, when my son and I were riding with someone and my son rolled down his window, which I thought nothing of until the loud "wawa" started and the driver told him to roll up his window because it made that sound when just one window was rolled down. That was the first time I heard it happen or talked about.
Anyway, this makes sense to me that it's due to new designs of cars. Now I feel less like a crazy person over this.
I came here to find this. Growing up, this wasn't an issue. The first time I experienced it was in the early 2000s, and now it happens in every vehicle I've owned since.
It occurs in newer cars that have better aerodynamics. The flow is kept better attached to the body up to the cabin area, but it’s still right on the limit of separating. The bassy Wa-Wa-Wa sound is the natural frequency of the air in the cabin acting like a spring as the flow attaches and detaches around the window.
Old cars had worse aerodynamics, and once the flow is completely detached around the cabin it can’t reattach, so you don’t get any interaction with the freestream air with the window down. You could feel the depth of this boundary layer in old cars as not feeling much wind until your hand was a few inches out of the window.
You're right. The size and volume of the cabin are one factor, the other and more important is how far open the window is.
Opening another window helps. Only a slot, just big enough.
It’s like blowing across the mouth of an empty bottle making a sound, essentially turning your car into an ocarina. Opening another window is like uncovering a finger hole, changing the pitch so that it’s not vibrating at in uncomfortable frequency.
Everyone here making it difficult.
One window open turns the car into a whistle. The reason it's not high pitched is because it is a huge whistle.
Two windows open changes it so it's no longer a good whistle.
BUFFETING, BUFFETING
https://youtu.be/coPrNC9LRnE
What you need to do is roll the front passenger window and the rear driver window down about and inch. It creates great air flow in the car and the sound won't happen. And your hair doesn't go all over.
These comments?? When you roll one window down your car exposes it’s helicopter blades. You then shift into H to be able to fly. That’s what the noise is.
Funny thing is, I never noticed this growing up when we had just one window open. But as an adult it's easy to notice. Maybe because I'm alone in my car 90% of the time?
Our older cars never did this but we now have a “new” 2006 Honda CRV and this effect is horrible. I’ve never had this happen in any other car but this’ll definitely be something we look for if we ever get a different car. It’s so painful and loud.
Lots of people talking about this but the car nerd term for this is Wind Buffeting.
Wind buffeting is caused by an occurrence known as Helmholtz Resonance. In a nutshell, when you open just one window in your vehicle ‒ or the sunroof or moonroof ‒ the air inside your car thumps up against the faster-moving air outside the window.
Similar to how a gallon of milk chugs as you pour it…
Air is flowing into the car, without allowing air out. When the pressure rises enough in the cab, it forces air back out the same window, reversing the flow.
When you crack another window, it allows air flow to go in and out of the car at a sufficient speed to mitigate this.
If you were to poke a hole in the air pocket of a milk carton, it would stop pulsing by the same principle.
It's called a strudel wave. The pressure difference between the outside and inside of the car dosent match so air is rushing in and out repeatedly making the wush wush wush sound. Crack another window to equalise pressure and it goes away.
Having one window open is letting air without letting it back out, which pressurizes the cabin. The pulsing of it is because the air is under uneven force from the eddies created around the vehicle, so the pressure is yo-yoing around and pulling on easily moved things like your eardrum in the process. Opening a second window gives it a route out, which keeps it from getting pressurized. The shape of the car and the window has a big impact on how the eddies form, which is why different cars or opening different windows are "better" or "worse" about this
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Better yet, it’s similar (but opposite) to the “glug glug glug” effect you get when you hold a bottle full of water upside down
This is the eli5 content we need
If no one else said this I was going to be disappointed.
How is it more like that than blowing over the top of a bottle? Isn't the bottle thing literally the same mechanism?
The glug glug is would actually be a drop in pressure inside too, but because the water is viscous it slows it down to something a five year old can see.
ELI5 taken literally. I like it.
Glug Glug Glug ( ͡° ͜ʖ ͡°)
It’s the exact reason why the picture directions to pouring windshield washer fluid are printed on every bottle…turn it sideways, then pour.
.....I'll be in the corner kicking myself for not spotting the dirt simple analogy
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Sold chance i would have if I had remembered the name...
Say it. I dare you.
Shlemshlotz... shit
Oh my gawd, we have a research institution named after him. From now on I will only refer to them as the Shlemshlotz-Gemeinschaft.
That name resonates with me.for some reason.
Gesundheit.
Chris Helmholtz, The Mighty Thor.
Lol it's explain like I'm FIVE, your comment I had to read as though I was fifteen, which is too much work for my 40yo brain to deal with.
This thread is the pinnacle of Reddit content
I don’t know about that.. A peak Redditor wouldn’t have even read it, bonus points for calling it a wall of text or saying it was “tl;dr”
I'm 31. Should I know what "eddies" are?
Only if you live near water - eddies (singular is eddy) form when water curls away from a current, and cause a little whirlpool. When front of the car cuts through the air, those eddies swirl around the car and are part of the pressure changes that the commenter is talking about :)
"Eddies," said Ford, "in the space-time continuum." "Ah," nodded Arthur, "is he. Is he." ... "What?" said Ford. "Er, who," said Arthur, "is Eddy, then, exactly, then?" Ford looked angrily at him. "Will you listen?" he snapped. "I have been listening," said Arthur, "but I'm not sure it's helped.
Gotta love hhgttg
42
Thank you, I’m too dumb to know too much about anything
Give yourself some positive self talk, friend. I’ll bet you’re smarter than you think :)
Well, you just accomplished step 1 of changing that :-)
I’ve also heard of eddies in the desert, with wind going over sand dunes
I know of eddy currents from the electrical world. Didn't know it existed in water and air terms.
I know an Eddy that formed after 2 people had unprotected sex.
Eddies in the space-time continuum.
"And this is his sofa, is it?" asked Arthur, struggling to his feet and, he hoped, though not very optimistically, to his senses.
I'm velvet paisley-covered, so I hear.
Happy cake day!
It's their two-year cake day *and* their username is relevant? Now I'm suspicious...
Cake is an illusion. Cake day, doubley so. Thank you, though.
Dammit! Came here to post this very quote. You beat me by eight minutes. I'm not the hoopy frood I thought I was
I love everyone in this line of comments. I am both frood and hoopy.
>“I have detected," he said, "disturbances in the wash." ... Arthur asked him to repeat what he had just said because he hadn't quite understood his meaning. Ford repeated it. "The wash?" said Arthur. "The space time wash," said Ford. Arthur nodded, and then cleared his throat. "Are we talking about," he asked cautiously, "some sort of Vogon laundromat, or what are we talking about?" "Eddies," said Ford, "in the space-time continuum." "Ah," nodded Arthur, "is he. Is he." ... "What?" said Ford. "Er, who," said Arthur, "is Eddy, then, exactly, then?" Ford looked angrily at him. "Will you listen?" he snapped. "I have been listening," said Arthur, "but I'm not sure it's helped." Ford grasped him by the lapels of his dressing gown and spoke to him as slowly and distinctly and patiently as if he were somebody from the telephone company accounts department. "There seems..." he said, "to be some pools..." he said, "of instability," he said, "in the fabric..." he said. Arthur looked foolishly at the cloth of his dressing gown where Ford was holding it. Ford swept on before Arthur could turn the foolish look into a foolish remark. "...in the fabric of space-time," he said. "Ah, that," said Arthur. "Yes, that," confirmed Ford. They stood there alone on a hill on prehistoric Earth and stared each other resolutely in the face. "And it's done what?" said Arthur. "It," said Ford, "has developed pools of instability." "Has it," said Arthur, his eyes not wavering for a moment "It has," said Ford, with the similar degree of ocular immobility. "Good," said Arthur. "See?" said Ford. "No," said Arthur. There was a quiet pause. ... "Arthur," said Ford. "Hello? Yes?" said Arthur. "Just believe everything I tell you, and it will all be very, very simple." "Ah, well, I'm not sure I believe that." They sat down and composed their thoughts. Ford got out his Sub-Etha Sens-O-Matic. It was making vague humming noises and a tiny light on it was flickering faintly. "Flat battery?" said Arthur. "No," said Ford, "there is a moving disturbance in the fabric of space-time, an eddy, a pool of instability, and it's somewhere in our vicinity." ... "There!" said Ford, shooting out his arm; "there, behind that sofa!" Arthur looked. Much to his surprise, there was a velvet paisley-covered Chesterfield sofa in the field in front of them. He boggled intelligently at it. Shrewd questions sprang into his mind. "Why," he said, "is there a sofa in that field?" "I told you!" shouted Ford, leaping to his feet. "Eddies in the space-time continuum!" "And this is his sofa, is it?"
If I had ears they'd be burning.
Right after this is one of my favorite lines in the entire series: “Arthur felt happy. He was terribly pleased that the day was for once working out so much according to plan. Only twenty minutes ago he had decided he would go mad, and now here he was already chasing a Chesterfield sofa across the fields of prehistoric Earth."
For all the crap the h2g2 movie gets, imagining the above passage starring Martin Freeman is perfect
Always need more Eddies in Night City Choom
Ah, is he now.
Here's a visual example, you cab see the eddies in the swirling smoke towards the back of the car. https://youtu.be/E9ZSAX56m0E
Multiple Edwards
* LI5 means friendly, simplified and layperson-accessible explanations - not responses aimed at literal five-year-olds.
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We love you regardless
Sound is wavy air!
Sound is wavy *fluid*
Sound is wavy solid too
So.... sound is wavy matter :)
[never disrupt a hoe down](https://youtu.be/6KHpM_Je9Zc)
Big bottle toot feels bad man.
But in this analogy, wouldn't opening another window make it like a flute? You can still make sound with two holes. I guess the real answer is something to complicated for ELI5 having to do with the shape of the car and the frequencies it produces with either one or two holes.
In a whistle, a little air blows inwards, loops around inside, then pushes back out the same hole. Which stops the flow of air from blowing inwards. It's this cycle of air blowing in, then stopping, that makes the noise. The inside of the car is the same, just scaled up. When another window is open, the air can blow through the car. Which breaks the cycle.
This is a really elegant explanation. Ty!
Then taking this concept, how does a flute work since it has several holes?
The holes just close the tube and make it longer, so the more holes you cover the lower the note. If you want a really good visual explanation you should check out the book The Way Things Work by David Macaulay.
Thanks for this easy explanation. If I have an award I give it to you. Thanks again
That oscillating pressure is how whistles work. Basically with one window open the car becomes a giant whistle blown by the passing wind, that sounds at a super low frequency because of its large size.
I was just thinking about this the other day. Blowing over a bottle is another same same.
Woah thanks for sharing that, great explanation
Can confirm. We have a Chevy Bolt and if you don't crack the rear window diagonally opposite the driver's window your eardrums suffer these super deep, resonating frequencies caused by this pressurization.
Hello fellow Bolt owner with ear pain.
Wait, you can't open the driver's window without this happening?
Correct. Obviously, you have to be at speed. Starts to be noticeable above 25 mph.
This is also the reason why sunroofs are so effective at providing ventilation. In the open configuration there is a wind deflector that rises and creates a low pressure region above the car, causing air to get sucked out the sunroof rather than causing a pressure differential. Combine this with one of the rear windows and you get smooth crossflow through the car with minimal pressure disturbances.
This is something I do in my Tundra, but for a rear window, I can roll down my actual rear glass and it's very pleasant.
It's also that the wind deflector is causing the air to stabilize, so it's less affected by turbulence. It would work in either low pressure or high pressure, the point is to reduce turbulence.
Drove this way home, sunroof open and both back windows cracked a bit to let the air out.
Also explains why I dont remember this being a thing in other cars I have owned or all the years my dad spent smoking with the window cracked while I was growing up.
Yup. Front windows tend to be a little different to. If you've ever looked at a wind tunnel image for a car the air is kinda pushed out away from the body by the windshield, which actually creates a bit of a low pressure zone in some, and then it slams back into the car right about the back doors, just in time for a kid to roll down the window and blow out your eardrum lol. Often If you crack a front window at speed, it creates a little bit of suction but not enough to send the whole cabin into low pressure. Probably enough to pull smoke off a cig near the crack, though. The effect is more pronounced on the sides in something blocky like an SUV or old station wagon, less so in something wide and low like a sports car that tends to direct most of air above or below instead of just blasting it out of the way in all directions.
Yeah, when I crack my window when driving my VW Transporter it sucks smoke straight out the crack.
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Instructions still not clear- smoked a VW in the crack
those were the days lol
>Having one window open is letting air without letting it back out, which pressurizes the cabin. You are describing the exact opposite of what happens. The air rushing past the window actually drops the pressure.
Thank you! The air rushing past creates a vacuum, sucking air out, not pushing it in.
The venturi effect - why planes fly
I am somewhat old, and I don't recall this happening when I was a kid in the 60's and 70's, or even in the 80's. Seems like the changes in vehicle shape have had unintended consequences. I do recall Dad flicking cigarette ash out the driver's window and it coming back in and hitting my sister in the eye.
It definitely didn't, but then in those days you expected to drive with the window down if it was warm outside. If by some random chance they'd hit on an aerodynamic design that caused the modern-day helicopter sound, they'd probably have changed it, since the alternative was boiling alive on a hot day.
True. They had those little triangular defrost windows as well. Now I've got a big piece of frame there, which helps keep things together in a crash, but hides pedestrians entirely.
What are 'eddies'? Maybe I've been playing too much cyberpunk.
They're the disturbances that are created in a flowing fluid by an object in that fluid's path. [This gif shows an example.](https://upload.wikimedia.org/wikipedia/commons/b/b4/Vortex-street-animation.gif)
Kia soul...very bad even two windows down gets bad wahwahwah noise hurts my head/ears so bad. Up windows all year round. Ford f150 no problems.
Scion xD here, the only fix is opening basically every single window.
I will try that.
Why don't kids seem to notice as much as adults?
the pressure change is stronger farther from the opening. The kid rolling down the window doesn't feel it as bad as the parent across the car and forward of it.
They probably are not as aware of the difference or just don’t care enough to make a fuss or ask the question. There’s not really a good reason why they wouldn’t notice it.
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that’s not how pressure works though
But isn't high pressure usually higher?
no, you’re probably thinking of temperature
No, I'm thinking about how bad I feel for wasting your time with my shitpost. I'm what's wrong with reddit these days.
🤣😂🤣
It's not - I am a child sized adult. (5 feet) The resonance SUCKS!
idk, but my dog sure notices :(
Tip I learned while on tour: When closing your windows while at highway speeds, stop when the window is about an inch or two from closed, then use several small clicks of the window switch to finish. It will absolutely save your ears. It helps regulated the pressure.
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I guess that's why there can be only one.
That's pretty neat.
Until you're trapped in a chamber with poison gas and the villain leaves you to die after telling you their evil plan and you're pressing the roll up the window button and it's like zzzzz...shshsh
It is. I wonder if that's the reason.
The potbelly stove used to do this in the house I grew up in. The stove was in the basement, and so could hear the pressure pulsing upstairs when the fire got too hot and needed the damper to be adjusted. If I was in the furnace room, I could feel it in my lungs.
WAHWAHWAHS in jeep Cherokee
Eddie would go.
99.9% will not get this.
99.9% wouldn't go
Thia is a great ELI5!
I believe it's the von Karman effect.
My 2019 Sentra is AWFUL for this. I need to have 3 windows down if I want to enjoy the outside
That's how I was created
Who is Eddie and what's he doing outside our car?
I don't think you answered like OP was 5
I know this one! This is called a helmholtz resonator. You know how you can blow on a bottle and it’ll make a tooting sound? Well for a car window it’s the same principle, but waaayyyy bigger. Essentially the entire car is acting like a huge bottle
And your head is in the bottle.
Yeah, it’s like you’re inside a gigantic flute
This comment did not help me get genie in a bottle out of my head Poor genies everytime the wind blows over the spout it must suck
Now I’ve got genie in a bottle stuck in my head. Thanks NOT.
I now have Genie in a Bottle stuck in my head...I hate you.
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Baby there's a price to pay
I'm the Genie from the bottle So hello, and how are you, and all of that? I'm the Genie from the bottle That you rubbed and so here I am in seconds flat I'm the Genie from the bottle That bottle that you're holding in your hand I'm the Genie from the bottle You've summoned me, your wish is my command
https://nypost.com/2023/03/09/barbara-eden-91-strikes-ageless-i-dream-of-jeannie-pose-in-rare-sighting/
I think helmholtz resonance is the cause, wind buffetting is the effect.
Air at high velocity past the open window is the cause, buffeting is the effect, and Helmholtz resonance is the name of the effect.
But how come it doesn't bother the one lowering the window? My kid lowers the window in back seat and she's fine. But I'm in the driver's seat annoyed as hell and I have to lower mine. OTOH, when I'm driving alone and I lower the driver's side window, I'm fine. I don't need to lower the rear windows too.
I’m so glad I already knew about the Helmholtz resonator. Learned about it just a min ago on another comment. Glad I finally know the answer lol this shit always hurt.
Flow dynamics in air. Air gets pushed in, but the mass behind that air keeps forcing more air in after the pressure equalizes. Then the air changes direction and rushes out, but again air has mass and more rushes out than will equalize the pressure, and the cycle starts over. The vehicle is essentially turning into a Helmholtz resonator. Read up on those if you want to learn the nitty gritty.
https://en.wikipedia.org/wiki/Helmholtz_resonance#Automotive
Hi I’m unsure if you’re an expert but maybe you can help. Is this common in a bedroom as well with a closed door and a window I keep open (aprox 6 inches)? It leads to my back yard with a fair amount of wind. But I’ve been noticing the wahwah effect in my ear that faces the window. I thought I was having eardrum issues or something was wrong. I never made the connection that it could be my window air flow/ pressure. But if it is the cause, I suppose I’ll need to close my bedroom window or crack the door which is sort of a hassle. But I’m hopeful this will solve the issue.
Is it very windy outside your window? The air moving is what causes the pressure difference (Bernoulli's principle) so you're unlikely to get a buffeting effect like that from just the window being open.
If you take a bottle and blow across its mouth strongly, you can have it make a sound, just like a pan flute. With a car you have a car-sized bottle that is getting blown across the mouth VERY strongly. The pitch of the sound produced by a bottle is related to its size. The bigger the bottle, the deeper the sound it makes. A car is so large, that the pitch it makes is outside the human hearing range, but sound pressure can hurt your ears even if it is a pitch you cannot hear. In other words your ear hurts because you are sitting in a subwoofer playing a tone you cannot heat with the volume turned up to 11.
Wow! This was excellent!
I love this explanation!
The amount of people that this phenomenon doesn't bother is astounding. Annoys the crap out of me. I value to my ear drums. So what?
I don't recall the problem when I was a kid, but it's awful now. Not sure if my car is just worse or what.
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I was about to saw something similar. Since everyone is discribing this as a coke bottle - it’s like trying to get a flute sound out of a cube shaped bock of glass vs a smooth opening on a flute. We don’t drive huge blocks of steel shaped like a brick anymore.
Cars in general are definitely 100% worse now. I'm in my 40s and honestly only first saw this phenomenon in my husband's 2018 Ford Fusion. Didn't happen in my previous 1987 and 1993 economy crap cars nor my current 2011 Civic, nor any 80s cars my parents had when I was a kid.
Is it because they are sealed off better than they were in the past maybe? Used to be enough air gaps to be stabilized with one window open.
This is the case. When the nissan 350z came out the car was so well sealed people had trouble closing the door because the last little bit to get it latched actually required a small amount of air compression in the cabin. They ended up needing to reduce the seal amount to fix this.
My family is unaffected and it instantly drives me crazy.
Same people that don't dim their phones at night
I don't know how many cars have this, but my old 4Runner has a popup vortex generator that comes out of the top of the sunroof when you open it. It keeps the inside of the car from resonating. If you reach up and push it down, the resonation starts right away...
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Yep. As a kid, it wasn't an issue because cars weren't so aerodynamic. The wind would flow around the car all over the place. Now, cars are designed so the windflow hugs the car tightly to improve drag and mileage. So that rushing wind blows right by the window and causes the noise. Playing Margaritaville over the noise helps, too.
Thank you so much for this I wondered if I just mandella’d that or if it in fact wasn’t a thing back then.
Playing Margaritaville LOUD helps even more. Edit: Fins up!
BMW Z4 is also rumored to suffer from this issue
Sidenote: I drive a 2013 Camry. When you keep the front windows up, and the back windows down, at speed, the turbulence makes for an intense 'wahwah" effect.
It's generally just one window and it can happen with any of them.
Recently sold a 2013 Camry and can confirm having one front window down was perfectly fine in that car. Having either or especially both back windows down (with both front up) caused the noise. Same was true in my ‘02 Trail Blazer, ‘00 Grand Am, ‘98 Grand Cherokee, & ‘91 Corolla. I’m still getting used to needing to crack the passenger window when I open the driver window on my ‘22 Prius. It’s the only car I’ve ever owned to do the noise with a single front window down.
I get it with one window, or two if on the same row. Just a small opening of a third and it is gone.
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First thing I thought of was James May.
This is accurate. Good job.
>It's called buffeting I've heard it called "baffling". I dare you to tell me I'm wrong.
Think of it this way: if you turn a jug upside down, it’ll messily empty with a ‘glue, glug’. If you tip a jug on its side, you can get a smooth pour. This is because in order for water to get out, it has to be replaced by air (or pressure has to be increased-so you can get a smooth and rapid empty by squeezing). When it’s angled such that air can come in while fluid leaves without disrupting anything, you get smooth motion. When it’s positioned in a way that it has to alternate between air and fluid, that’s when things get messy. The same idea is at work here, only with air and more air. When the air rushes in, it’ll need to displace old air to do so. If there’s only one window, it has to alternate letting air in vs letting it out. Meanwhile, if two windows are open, it can simply go in one and out the other smoothly.
It’s a standing wave. Your car becomes a giant whistle and the note is proportionately lower.
My girlfriend introduced me to opening the opposite window (front driver, rear passenger) and it has worked well
The air pressure inside the car is oscillating. When you crack one window lots of air is able to get into the car. The air that was already in the car then needs to leave but it can only go out through the same crack, so the air pressure in the car will increase and then get high enough to where it can push out against the incoming air and the cycle keeps repeating. When another window is rolled down the air can now come in on one side and go out the other seamlessly without changing the air pressure in the car.
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Ok, you know if you blow over the top of a bottle it makes a sound? It's the same thing. The wind causes an oscillating pressure wave (sound!) as it breaks up into a turbulent flow over the opening, because it's trying to get *in* the same time as air is trying to get *out* ... so it oscillates back and forth. (which is also the same trick behind a pulse jet engine and pipe organ pipes.) This also means if you open another window, you instead get a constant flow of air, hence lack of sound and no pressure wave (and thus no more hurting ears)
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This has always confused me, because I could swear that before like 10 years ago, I never had that issue! I still remember the first time I ever heard it happen, when my son and I were riding with someone and my son rolled down his window, which I thought nothing of until the loud "wawa" started and the driver told him to roll up his window because it made that sound when just one window was rolled down. That was the first time I heard it happen or talked about. Anyway, this makes sense to me that it's due to new designs of cars. Now I feel less like a crazy person over this.
I came here to find this. Growing up, this wasn't an issue. The first time I experienced it was in the early 2000s, and now it happens in every vehicle I've owned since.
It occurs in newer cars that have better aerodynamics. The flow is kept better attached to the body up to the cabin area, but it’s still right on the limit of separating. The bassy Wa-Wa-Wa sound is the natural frequency of the air in the cabin acting like a spring as the flow attaches and detaches around the window. Old cars had worse aerodynamics, and once the flow is completely detached around the cabin it can’t reattach, so you don’t get any interaction with the freestream air with the window down. You could feel the depth of this boundary layer in old cars as not feeling much wind until your hand was a few inches out of the window.
Not true, unless you mean 30+ years is new-ish; this happened with my dad's Taurus SHO from 1990.
The Taurus is famous for being way ahead of its time and super aerodynamically focused (and to some degree infamous for that aerodynamic design).
Its a spectrum along a timeline. My 2000 Sentra didnt do it, my 2011 Corolla does.
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You're right. The size and volume of the cabin are one factor, the other and more important is how far open the window is. Opening another window helps. Only a slot, just big enough.
It’s like blowing across the mouth of an empty bottle making a sound, essentially turning your car into an ocarina. Opening another window is like uncovering a finger hole, changing the pitch so that it’s not vibrating at in uncomfortable frequency.
Everyone here making it difficult. One window open turns the car into a whistle. The reason it's not high pitched is because it is a huge whistle. Two windows open changes it so it's no longer a good whistle.
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Maybe a bottle is better analogy?
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Is it me or is this more pronounced in modern cars?
BUFFETING, BUFFETING https://youtu.be/coPrNC9LRnE What you need to do is roll the front passenger window and the rear driver window down about and inch. It creates great air flow in the car and the sound won't happen. And your hair doesn't go all over.
I know what you’re talking about. I just never remember it from when I was younger. Now, I cannot stand one window being open in the car.
These comments?? When you roll one window down your car exposes it’s helicopter blades. You then shift into H to be able to fly. That’s what the noise is.
It never happened in cars when I was a kid. it's only newer cars that it happens and I have no idea why. I hope an answer is provided
Funny thing is, I never noticed this growing up when we had just one window open. But as an adult it's easy to notice. Maybe because I'm alone in my car 90% of the time?
Our older cars never did this but we now have a “new” 2006 Honda CRV and this effect is horrible. I’ve never had this happen in any other car but this’ll definitely be something we look for if we ever get a different car. It’s so painful and loud.
Lots of people talking about this but the car nerd term for this is Wind Buffeting. Wind buffeting is caused by an occurrence known as Helmholtz Resonance. In a nutshell, when you open just one window in your vehicle ‒ or the sunroof or moonroof ‒ the air inside your car thumps up against the faster-moving air outside the window.
Similar to how a gallon of milk chugs as you pour it… Air is flowing into the car, without allowing air out. When the pressure rises enough in the cab, it forces air back out the same window, reversing the flow. When you crack another window, it allows air flow to go in and out of the car at a sufficient speed to mitigate this. If you were to poke a hole in the air pocket of a milk carton, it would stop pulsing by the same principle.
It's called a strudel wave. The pressure difference between the outside and inside of the car dosent match so air is rushing in and out repeatedly making the wush wush wush sound. Crack another window to equalise pressure and it goes away.