Electric Cars- Why are they so quiet?

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Ottobon

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Just popping in and wondering out load why electric cars are always quiet when infact i've spent my life around rather noisy plug in drills, R/C cars, and other electrically powered stuff. I much prefer the sound of a powerplant to the hateful sound of tire and wind noise, but seeing as all the electric cars made thus far have had silent engines i see them all as unforgivably bland and hopeless.

What I'm wondering is if the silence is something thats been engineered in, or if for some weird reason really large and powerful electric motors don't make noise (that 2nd idea doesn't make sense to me) I wouldn't mind electric power if from in the cabin it sounded like a really angry power-drill, but you don't even get that, you get nothing.
 

JipJopJones

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Just a guess, but I think it has to do with the type of transmission used. In power tools it is the gears of the electric motor you are hearing. But with the car I beleive it uses a Continuously variable transmission. Thus no gears... thus no noise... but that's just a wild guess.
 

katwalk

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Yeah they should sound like a fucking death ray or something. Now that would be cool. I will miss the snarl that even my tiny bug gives when it takes off.
 

NecroJoe

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Sounds like you need the Brabus Tesla Roadster. It comes with a engine and a space warp sound.

I'll bet a lot has to do with the design. It's probably made to be quiet. Who cares if a drill is quiet?
 

jackernapes

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Hm, interesting point...

I think its definitely something to do with the gearbox though. I mean, if you think about it, "straight-drive" electric motors make nearly no noise at all. Think of an electric fan, 'cept without the fan bit.

And if you think about the amount of noise a normal car gearbox makes, its really not that much, even with all the engine noise around it.

So bigger gears plus more lubrication (transmission fluid, etc) probably equals less noise somehow.
 

NecroJoe

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And if you think about the amount of noise a normal car gearbox makes, its really not that much, even with all the engine noise around it.
Unless you're in reverse...because of the "shape" of the forward gears, they are very quiet. In reverse, you hear that sort of "whine" noise as you accelerate.
 

Shawn

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Unless you're in reverse...because of the "shape" of the forward gears, they are very quiet. In reverse, you hear that sort of "whine" noise as you accelerate.
Interesting you brought that up.

Aside from the original question which I'm wondering about now, I'm also wondering, why do some cars make much more of a whine noise when in reverse?

I've noticed FWD Japanese cars make the loudest. My RSX sounded like it wanted to explode if you put your foot down in reverse.
 

NooDle

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^my car makes a whole lotta noise if you go in reverse quickly, I like the sound.

With regards to the electric cars : it's a combination of factors. first, the engine sound is gone, obviously. You don't need a gearbox or driveshafts so those can't make much noise either. And thirdly I do think some cars are engineered to be quiet on purpose. It's weird watching/hearing a Tesla being driven because it's unnatural
 

jackernapes

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As for the "louder in reverse" question, its not necessarily the shape of the gears, but how many are being engaged

If the engine were hooked up directly to the wheels, crankshaft to driveshaft, the car would run backwards. When you run the engine through the gearbox to the wheels, the car moves forward, 'cause meshing gears turn in opposite directions of course :p

So in order to reverse the car, you have your reverse gear, with the powered gear and the driven gear, and another "idler gear" in between them to reverse the rotation of the wheels. Seeing as you have another cog in the mix, its gonna be a little more noisy.

Probably also has something to do with the shape of the gears too tho :\
 

WillDAQ

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The reason the idler gear is so noisey is due to it's geometry (size, width, teeth etc).

For an electric drill most of the noise is coming from the gearbox as it's built down to a price. Obviously on an electric car you can spend a lot more on bearings and similar so you get a quieter product. Plus of course the RPMs involved are much lower.
 

The_Finn

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The reason reverse makes that whine is straight cut gears normal forward gears are helical cut which gives up a bit of strength but allows for a smoother engagement and therefore less noise. If you have ever been in a car with a straight cut gear box it sounds basically the same (see video) as reverse

[youtube]http://www.youtube.com/watch?v=dmJH84FnQa8[/youtube]

[youtube]http://www.youtube.com/watch?v=v6Ce_JywGFU[/youtube]
 

73GMCSprint

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2 words: Brushless motors.

I'm sure the gearbox/CVT has a lot to do with it too though.
 

NecroJoe

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Forward gear shape:


Reverse gear shape:


Notice how the "forward" gears are cut on an angle? This lets the gear grab a bit at a time, which...for some reason makes it quieter. I'm not going to pretend I know why, I just know it does...
 

The_Finn

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Forward gear shape:


Reverse gear shape:


Notice how the "forward" gears are cut on an angle? This lets the gear grab a bit at a time, which...for some reason makes it quieter. I'm not going to pretend I know why, I just know it does...
It's called helical cut and straight cut respectively. The sound difference has to do with the load being put on the gears. Helical alows of comparatively gradual engagement where as straight cut the gear faces "slap" into each other all at once.
 

jackernapes

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The reason reverse makes that whine is straight cut gears normal forward gears are helical cut which gives up a bit of strength but allows for a smoother engagement and therefore less noise. If you have ever been in a car with a straight cut gear box it sounds basically the same (see video) as reverse

Ah-HA!!

so THATS why the BMW M3-GTR has that distinctive sound. I always knew it was the gearbox, but i was never quite sure why it made that beautiful sound.

NOW YOU KNOW!
 

Matt2000

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Unless you're in reverse...because of the "shape" of the forward gears, they are very quiet. In reverse, you hear that sort of "whine" noise as you accelerate.
I get that in all gears.




What?

Something to say?

:p


Anywa I guess it's just the fact that electric motors are quiet and they don't have many gears. Also you've not got the vibrations of an engine.
 

TestECull

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I say mandate straight-cut gears in EVs. Solves every noise-related problem with them, and it might just annoy their owners to the point we stop trying to power a full size car with batteries and come up with a green method for extracting H2 to put in our big block V8s.
 
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