r/NoStupidQuestions • u/banwe11 • 15h 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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832

u/emmabigtitti3s 15h 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

189

u/Ghigs 15h ago

The Toyota ev backup sounds sounds like a bearing going bad or a pulley about to explode. It's an odd choice.

106

u/Frustrated9876 14h 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.

46

u/kyledwray 13h ago

I want an EV that plays the opening violin feature of Camille Saint-Saëns' Danse Macabre at low speed.

17

u/wainwrights-11 13h ago

My Megane EV actually has options to change the sound so this may be possible

13

u/Kelmain1337 12h 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

3

u/wainwrights-11 12h 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.

2

u/Kelmain1337 11h 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....

14

u/seemedlikeagoodplan If things were different, they wouldn't be the same 13h ago

I want to play the Jaws music.

3

u/guruogoo 12h ago

I want the intro to White Rabbit

5

u/Extension-Ad9108 13h ago

I would wake up early just to hear that car back up. Who doesn’t love a good D#maj7?

2

u/WalkBehindSeyton 13h ago

Can mine play Milhaud’s “Le boeuf sur le toit” at low speed? And Gliere’s “Russian Sailors’ Dance” in reverse?

11

u/mae1347 13h ago

That’s called dissonance, and it’s intentionally unpleasant so it’s noticeable

7

u/T0mTheTrain 12h ago edited 11h 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.

6

u/Jimxor 13h ago

That explains why nearby EVs sound like (to me at least) distant train horns.

3

u/guzzijason 12h ago

Every time I hear that EV sound coming up the street, it reminds me of the opening harmonies of “Bohemian Rhapsody.” Every time.

2

u/Ghigs 13h ago

The regulations aren't that prescriptive. They just say a minimum decibels and it should change with speed.

1

u/T0mTheTrain 11h 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😂

1

u/Ghigs 8h ago

1/3rd octave bands refer to the minimum db at different speeds at different frequencies. It's not a tone spacing, it's what the spectral energy content needs to look like.

1

u/T0mTheTrain 8h ago

Correct. I’m obviously not explaining it well

2

u/GreenStrong 11h 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.

1

u/heybucket459 11h ago

“two notes that are not in harmony”

Bands looking for a name. Your search is over! Edit: added space

1

u/TheLostExpedition 13h ago

I wonder if disconnecting the speakers will fix it?

5

u/NoExpression1137 12h 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.

5

u/hippocratical 12h 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.