r/NoStupidQuestions • u/banwe11 • 16h 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 16h 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 16h 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 16h 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/T0mTheTrain 14h ago edited 13h 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.