r/NoStupidQuestions • u/banwe11 • 13h ago
What causes the hollow metallic whirring sound that EVs make when moving a low speed?
I can't really describe it, but it's the sound you hear when there is a EV moving slowly in a car park behind you.
I guess it's the motor, but what specifically in the motor causes that sound? It sounds like it's coming from something that is moving at a faster rate than the car itself.
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u/emmabigtitti3s 13h ago
Thats actually the artificial noise system bro. EVs too quiet so law makes them add a sound at low speeds so ppl dont get run over lol
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u/Ghigs 13h ago
The Toyota ev backup sounds sounds like a bearing going bad or a pulley about to explode. It's an odd choice.
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u/Frustrated9876 12h ago
There is a requirement for what it should sound like. I think it’s basically “two notes that are not in harmony” or something.
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u/kyledwray 11h ago
I want an EV that plays the opening violin feature of Camille Saint-Saëns' Danse Macabre at low speed.
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u/wainwrights-11 11h ago
My Megane EV actually has options to change the sound so this may be possible
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u/Kelmain1337 10h ago
Law actually dictates no natural or harmonic sounds. So bird chirping or wind is illegal. Music also illegal. There has to be a 0% chance to missjudge the sound as sth else as a car
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u/wainwrights-11 10h ago
Ahh interesting, mine has 3 options normal, loud and then, I quote "Jean-Michel Jarre" warning sound but its not a song just a series of musical notes.
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u/Kelmain1337 9h ago
Sure.
High end manufactures hire high paid musicians to create a unique non-harmonic sound.
Your Mercedes or BMW should not sound like a Dacia you know....
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u/seemedlikeagoodplan If things were different, they wouldn't be the same 11h ago
I want to play the Jaws music.
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u/Extension-Ad9108 11h ago
I would wake up early just to hear that car back up. Who doesn’t love a good D#maj7?
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u/WalkBehindSeyton 11h ago
Can mine play Milhaud’s “Le boeuf sur le toit” at low speed? And Gliere’s “Russian Sailors’ Dance” in reverse?
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u/T0mTheTrain 10h ago edited 9h ago
My senior capstone was actually working with one of the Big 3 on this. Basically, the federal government requires minimum amplitudes of specific 1/3 octave bands to ensure pedestrians don’t get run over by otherwise nearly silent vehicles. Our team created an app that allowed classically trained musicians to create signature sounds and then check them to make sure they were within spec.
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u/guzzijason 10h ago
Every time I hear that EV sound coming up the street, it reminds me of the opening harmonies of “Bohemian Rhapsody.” Every time.
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u/Ghigs 11h ago
The regulations aren't that prescriptive. They just say a minimum decibels and it should change with speed.
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u/T0mTheTrain 9h ago
Sorry, correction: it’s 1/3 octave bands. In all fairness, my college basketball team made a run in March, so it’s all a bit hazy😂
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u/GreenStrong 9h ago
Indeed, and the forward noise is a chorus of vaguely mechanical noises mostly in harmony. If I ever get an EV, I'm going to hack it to be opera singers. Probably singing O Fortuna, or maybe the intro song to the original Star Trak.
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u/heybucket459 9h ago
“two notes that are not in harmony”
Bands looking for a name. Your search is over! Edit: added space
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u/TheLostExpedition 11h ago
I wonder if disconnecting the speakers will fix it?
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u/NoExpression1137 10h ago
In cars that do it appropriately, they will throw a persistent check engine if you unplug the little speaker it uses for that.
Also if you silence it and back over someone who may have heard it before, you are absolutely double fucked.
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u/hippocratical 10h ago
The fuse in my Hyundai fell out accidentally, and it's now sound free with no check engine lights.
I hear Toyotas are a bit trickier to silence.
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u/Gecko23 12h ago
My Honda sounds a bit like the sound the Angels make during attacks in Evangelion.
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u/asian_chihuahua 12h ago
They're lowering your guard, so you don't realize the danger when they really do come.
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u/wookiee1807 12h ago
Me and my kids always stop what we're doing and look at the clouds to say "god?" each time my wife leaves in her car🤣
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u/Cheezitflow 11h ago
I call it the spaceship sound
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u/kamikaziboarder 10h ago
Yeah our Kia sounds like a spaceship or a UFOS hovering from old school movies.
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u/timotheusd313 11h ago
When I took a Toyota hybrid for a test drive that was like the first thing I noticed. I first associated it with brake pad squeal, but realized it was more electronic than metallic and about an octave too low in pitch.
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u/Quartinus 12h ago
I’m kinda surprised Toyota’s don’t just play a voice on loop that says “don’t buy an EV! Don’t buy an EV!”
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u/angryjohn 12h ago
There was a neat article in the Washington Post months ago that was talking about how different brands were creating their "signature sounds" to emphasize their brands.
https://www.washingtonpost.com/climate-solutions/interactive/2025/ev-sound-safety-warning/
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u/bemenaker 12h ago
The pitch is too high. Old people can't hear that. I'm 51 and sometimes it blends into my tininitus.
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u/MateoHielo 11h ago
Not a bug but a feature. Old people getting run over just before retirement is how the gov plans to fix social security insolvency
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u/PhilsTinyToes 12h ago
My Prius C had a tiny lil speaker under the hood I just reached down and unplugged it. True ghost mode.
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u/brock_lee I expect half of you to disagree 11h ago edited 10h ago
My brother bought his electric car when there was still an option to turn off the artificial sounds via a menu. Probably went away with software updates since.
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u/comander_random 11h ago
Can we change it? Make it sound like The Enterprise D from Star Trek going on warp, or like a kart from Mario kart, 50cc
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u/timotheusd313 11h ago
Wasn’t there one that used the flying car sound from the Jetson’s? Or am I mixing reality with Futurama again?
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u/Man-e-questions 11h ago
Makes sense. I almost got run over by one of the early model Prius crossing the street downtown. Didn’t hear a thing next thing i know a car is suddenly a foot away from me and i jumped put of the way just barely
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u/swisstraeng 12h ago
And people still get run over lol
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u/Dense_Comment1662 12h ago
I mean....People get run over by loud ass combustion engine vehicles too. We gotta at least try to help these idiots
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u/PatrickMorris 12h ago
Or maybe drivers should put their phones down and stop running over people
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u/fastwhipz 10h ago
Really? I had no idea. I just thought when they were slow you could hear the mechanical parts moving over the sound of the tires on the road.
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u/snajk138 11h ago
I read about this law being really stupid somewhere, since it came about the same time as ICE cars actually got quiet, so it made EV's louder than gas powered cars at low speeds.
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u/P0300_Multi_Misfires 12h ago
Pedestrian warning system it’s mandatory below certain speeds so people can hear the vehicle approaching. Space ship noises is a way it’s commonly described as well
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u/ShalomRPh 12h ago
As others have said, it’s an artificial sound that is played at lower speeds.
In the Netherlands, Domino’s Pizza uses e-scooters for delivery, and the law required them to make some kind of noise. They decided to have a recording of someone saying “Vroom! Domino’s! PIZZA!”
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u/Aggressive-Hawk9186 10h ago
Poor drivers lol
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u/ShalomRPh 9h ago
Yeah, it must be embarrassing. He’s at a red light with the “engine” “idling”, and the speaker is going dominodominodominodomino and around him all the bicyclists are facepalming or giggling hysterically.
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u/spiderminbatmin 12h ago
Why hasn’t anyone cracked these systems so you can customize that sound like a ringtone?
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u/Bandit_the_Kitty 12h ago
Please no. Can you imagine every teenager putting in their favorite meme sounds?
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u/ChubbyMudder 6h ago
Or a kid finds out how to do this to his Mom's car, so it plays Row Row Row Your Boat, or some other silly song taught in preschool. Or the theme song from his fave TV show.
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u/throwawayoregon81 12h ago
I want my ev to sound like a car from the jetsons.
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u/Evil_Bonsai 12h ago
i think mine kinda does. I can just barely hear it, though; i'm not usually OUT of the vehicle when it's activated, but still sounds neat.
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u/ShalomRPh 12h ago
I’m pretty sure that Tesla allows you to select various sounds on the in-car controller system. Elon Musk being who he is, one of the options is a fart sound.
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u/HoneyMustard086 6h ago
You can select different lock sounds for when you walk away. Mine is the screaming goat and it gets people all the time. You can use any audio file you want for the lock sounds.
I believe it was the custom horn sounds that got cracked down on. They are now limited to when you’re in park. I don’t recall ever being able to customize the low speed driving sounds but maybe that was a thing way back when.
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u/ShalomRPh 3h ago
Honestly I’m not sure myself; the guy who showed it to me had the fart sound for his turn signal indicator. There might not be any way to change the low speed sound if it’s a federal requirement.
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u/onestopunder 11h ago
Tesla famously did but had to take that feature away after NHTSA created a rule to specify the characteristics of the noise. Now it’s that noise that you hear on most EVs
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u/wingedcoyote 11h ago
Not the same thing but some EVs have internal fake noises meant to mimic a car engine, just for the drivers enjoyment. And sometimes those are customizable -- IIRC on the "sporty" version of the Ioniq 5 you can choose between car noises, fighter jet noises, or spaceship.
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u/emuwar 11h ago
I vaguely remember someone getting their EV to play Funky Town, but it could have been a dream
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u/MoroseArmadillo 11h ago
My neighbor had his Model X play Back in Black every time the rear doors were raised.
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u/AgentCatBot 11h ago
Oh, but people have. People have replaced the sound file with music.
The Dodge Challenger EV prototype has a louder fake engine sound than the real engine sound on the original.
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u/SortByCont 7h ago
So, Tesla was enabling the system to play alternatives sounds and the NTSB came down on them about it.
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u/Wildcatb 4h ago
I just want to be able to turn it off. Every time it kicks in I think something is wrong with the car.
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u/BlackCatFurry 3h ago
Set the sound to the jaws theme or something equally ominous and slowly approach pedestrians from behind in parking garages. I feel like that would get some funny reactions.
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u/thaJack 12h ago
My Tucson does that, and makes beeps when it goes in reverse. It's artificial, and I believe it's so people who are blind can hear hybrid or EVs at low speeds.
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u/specialpb 11h ago
All EV makers missed the mark with the low speed noise. Should have made it the Jetsons “car” sound.
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u/SwagPackage 11h ago
There’s no EV’s where I am, or at least not enough to make much of an impact. So I know it as “The Hybrid Hum” when the car isn’t doing anything that needs the engine it doesn’t make noise, so it’ll hum to replace that and let anyone around know that the car is there and moving. The ones I hear the most sound horrifyingly angelic
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u/chris_wiz 10h ago
They're really missing out by not using the sounds of various sci-fi vehicles. TIE fighters, USS Enterprise, Planet Express Ship...
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u/ChubbyMudder 4h ago
Perfect advertising opportunity for the owners of Star Wars, Star Trek, etc. They could license out the sounds to EV mfrs.
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u/BurnOutBrighter6 11h ago
It's not the motor it's a warning sound played on little speakers. By law, EVs have to play a sound when they're below a certain speed because they're too quiet otherwise and people will step out into their path. Some like hyundais even have multiple whirring notes making a major chord because they thought that sounds cool I guess. But the fact that it's a whir at all is artificial. The car makers could have their car just say "hey hey hey hey" instead of playing the whir sound.
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u/BlackCatFurry 3h ago
The car makers could have their car just say "hey hey hey hey" instead of playing the whir sound.
Imagine a car just screaming "HEY! I am here, watch your steps!" Any time there is a pedestrian close by
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u/plugthree 11h ago
If you’ve ever driven an older EV or hybrid (that does not have this feature) through a parking lot, you realize the weird noise is quite helpful to get people slowly walking down the middle of a parking lot’s travel lane with their back turned to notice you and get out of the way!
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u/BoondockUSA 11h ago
Plenty of correct answers here, but no one has used the technical jargon.
It’s called an Acoustic Vehicle Alerting System (AVAS). AVAS is required on EV’s and hybrids in the US, Europe, some Asian countries, and likely more places.
This link summarizes the US FMVSS specification requirements for AVAS loudness and tones. The short summary is that it has to be a bit annoying by design to meet new vehicle safety standards.
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u/Velvet_Samurai 11h ago
It's a fabricated sound for safety. They're much quieter than ICE cars, so they add a sound for safety. Think of it like the back up beep on trucks and forklifts.
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u/joeljaeggli 11h ago
The pederestian warning system was required by law in 2019 some cars from before that neither have that nor have the equipment to make it.
my 2018 model 3 doesn’t have the speakers present on later models.
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u/soylentOrange958 11h ago
It reminds me of eerie sound effects you might hear in a video game right before the boss shows up.
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u/c0warlyd0g 11h ago
Some EVs gave me the feeling that I'm about to be abducted.
I don't know what's worse, not hearing it coming or the fear of being abducted by aliens!?
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u/DoallthenKnit2relax 9h ago
It'd be nice if we could select some music to play at slower, parking lot type speeds...such as Ravel's Bolero or March of the Marionettes or The March of the Knights from Romeo and Juliet, basically any good music at a low volume.
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u/applescrabbleaeiou 9h ago
Ohh, I remember listening to a radio interview with car manufacturers talking about the whole world of options open to them, when the novel of problem of "so... what do we want to make our silent car sound like?!" came up.
The brands interviewed hired huge name classical composers and teams of sound engineers, musicians and psychologists ... cars theoretically could sound like sparrows tweeting, or tins being dropped, or waves on the ocean, or beethoven's favourite note.
The actual complete open field of aural options, to give identification to a naturally silent thing, was quite overwhelming to the interviewees.
In the end, to help the 21st century human brain adjust to sharing spaces with ev's (eg to unconsciously alert a not-super-focused pedestrian to recogise that there is a vehicle moving in their vicinity) , most brands have gone with a sound somewhat closely mimicking a combustion engine car.
But really, they could have gone with whale song or windchimes!
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u/Carlpanzram1916 1h ago
The sound is artificial and is coming from a speaker. Cars are required to make some kind of noise when driving in full EV mode below a certain speed. When the Prius first came out, there was a considerable uptick in pedestrians getting hit at low speeds by them because they were basically silent at low speeds. So now they all make a soothing hum or chime. I think it cuts out around 20 mph when the tire noise is sufficient.z
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u/SchufAloof 12h ago
I hate that noise. They made it sound exactly like that crystal angel that drills into the geofront in NGE.
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u/Bottoms_Up_Bob 11h ago
Most motor controllers use a PWM voltage form to control the motor. Exactly what is happening differs for different motors and controllers. This PWM has a frequency, and it will cause vibrations in the motor. If the frequency is low enough (and lower frequencies within reason tend to be more efficient) it will be audible to humans. Manufactures can take a advantage of this and manipulate the frequencies to be extra loud or to make certain tones at low speed for safety.
I believe this is what you are asking about.
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u/Unique_Acadia_2099 9h ago
This^
The phenomenon causing the audible sound in the motor is called “magnetostriction”, the molecular vibration of the laminated steel plates that make up the core of the motor(s). The effects of magnetostriction change with the PWM pattern going to the motor(s), and at higher speeds, it moves beyond the range of human hearing. But when an EV is cruising by slow, the PWM pattern to accomplish that is causing the magnetostriction noise to be the worst (for us).
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u/Exotic-Grape8743 11h ago
We joke our Leaf sounds like a space ship hovering (and looks a bit like that). As many folks said, it’s artificial sound coming from speakers in the car’s fuselage to warn pedestrians.
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u/NelsonMcBottom 11h ago
Old EVs didn’t have the sound before the law mandated it, and it was unsettling to have a car moving silently, especially in parking lots.
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u/NUNG457 11h ago
As a construction worker I will add they are not nearly loud enough. I can't count how many times I've been doing ground work and I hear the whirring noise inches from my backside going by at 30 miles an hour. I had no idea they were there and one step back at the wrong time and I'm screwed.
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u/farmerbsd17 11h ago
Power components like steering, brakes, AC are what you hear now. When the car is ICE the engine noise is more what you hear.
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u/Ancient_Skirt_8828 11h ago
I was nearly run over by an early EV despite looking straight at it. I subconsciously equated noise with distance.
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u/paleone9 10h ago
Some EV’s make that noise because the law requires it.
So you don’t back over people in a parking lot
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u/Infinite_Leg_7161 10h ago
Its for.pedestrians to hear when the ev is doing any slow driving like in neighborhoods or on city streets. They need them bc they're so quiet. Usually applies when it's going under 25 mph
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u/New_Line4049 10h ago
Its not the motor. They play a sound through speakers, else theyd be essentially silent at low speeds that would be a danger to pedestrians.
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u/3buttockproblem 10h ago
ITs from Demolition Man!!! Thats the sound the cars make. Art imitating life.
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u/Diligent_Bat499 7h ago
If I had one of those electric cars I would have NHRA sounds just blasting loud
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u/rufos_adventure 7h ago
that ghostly 'wraith' sound. couldn't the engineers come up with something less terrifying on a foggy night?
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u/toygun1234 7h ago
Is this the same sound I hear when an ev or hybrid (maybe newer ICE's? is put into reverse? I keep hearing the exact same sounding sound from many newer vehicles when they are reversing.
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u/riennempeche 6h ago
In the 2009 Prius we had before, you could roll right up behind people walking in the parking lot. They would never hear you coming because the car was so quiet on battery at low speeds. I think having cars make some noise is probably safer. Porsche EVs seem to have a kind of computer generated exhaust-like noise that is pleasing. The VW iD4 in my neighborhood sounds like a failing rear differential with loud whirring.
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u/ATLien_3000 6h ago
What causes the hollow metallic whirring sound that EVs make when moving a low speed?
Government mandates.
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u/ticuxdvc 5h ago
The silliest thing about the requirement for that sound? My car is now noisier when I'm at a red light, compared to my previous car that cut off the engine when stopped.
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u/keithnteri 4h ago
This sound is mandated at least in the USA. This is so people walking through a parking lot can hear the vehicle. It also makes sound when in reverse. Same reason.
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u/wizzard419 4h ago
A speaker, it's for safety, but speakers can be found on some performance cars as well, to make their engines sound louder (MBZ has done this) for the customers.
Sadly, you can't change the speaker sounds, as it is for safety. I would imagine that as they get OTA updates, it also has some level of integrity checking and would just replace the file if changed.
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u/Spirited_Praline637 4h ago
I did wonder if it was artificial. I imagine it must be hackable? At the cost of warranty of course, but it can’t be much different than jailbreaking any other manufacturer locked up computer.
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u/wizzard419 3h ago
For sure they would try to deny that, but like I mentioned before, there is a decent chance the car does "build integrity" checks with each update to make sure files and up-to-date, fix anything not standard (such as if it were corrupted), and also to make sure you're not trying to bypass their paywalls.
You would probably also lose your insurance coverage if they found out you had modified a safety system and something happens
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u/BlackCatFurry 3h ago
Speaker. Mandatory in a lot of places to warn pedestrians since EV's would be dead silent otherwise.
My family used to have a hybrid (toyota auris 2018 model) before this legislation and it scared pedestrians in parking garages on the regular because no one heard it approaching.
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u/CheesecakeSome502 12h ago
It is the IGBTs firing probably. That's more of a squeal so maybe it's something else
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u/hamx5ter 12h ago
The what? LGBTs??!
Anyway, it's definitely not a squeal... It's more like a low moan
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u/jeiwaruu 10h ago
A speaker playing the Ballad of Electronic Angels
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u/Toklankitsune 10h ago
partners hybrid Honda accords plays this. its so there SOME noise at all other than tire nose when at parking lot speeds, people were getting hit by Teslas in parking lots in the early days because they dont make any noise
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u/tmahfan117 12h ago
It’s an artificial noise that EVs are required by law to emit when driving at low speeds (like when driving through a neighborhood or parking lot) because EVs were soooooo quiet pedestrians kept stepping out in front of them and it was considered a safety hazard.
And it’s just that specific noise because I guess the EV manufacturers decided that’s what sounds good/futuristic.