Why do all EVs make the same quiet hovering sound when they drive ?
In: Engineering
Curiously our friend’s new EV9 has a “no sound” option for going forward. So it must not be a federal mandate for forward travel. Our 2021 Tesla is also dead silent in forward.
They don’t, and it’s not an engineering question. Federal regulations are still out from what I recall on actually mandating this. But the sound is so that there isn’t a 4 thousand pound chuck of metal capable of crushing a pedestrian wondering around silently.
In my head, Congress watched Weeds and saw this scene:
Nancy: You bought a Prius?
U-Turn: I bought seven of them. I got my whole crew driving them. They’re real quiet. Good for sneaking up on motherfuckers. [hand motions drive-by]
Law in 2019 made it mandatory for pedestrian safety during reverse. It’s an external speaker that’s making the sound.
If you hear it going forward, the manufacturer of that brand opted in for going forward as well.
EVs make noises during operation because they are required to by law. It’s not the same sound across cars, but typically the same across vehicles of the same make. The EU parliament and US National Highway Transportation and Safety Administration both made rulings requiring electric cars, and hybrid cars operating in fully electric mode, to make sounds while operating. The reason is very simple: without sounds the cars are nearly silent, which is a risk to pedestrians, particularly those with vision problems that rely more on sound to detect cars as a hazard.
In the USA, this is called the “Acoustic Vehicle Alerting System” and consists of speakers built into the frame of the car to make sounds to alert pedestrians
Podcast on the subject (with examples of sounds used by different manufacturers): [https://www.20k.org/episodes/autotone](https://www.20k.org/episodes/autotone)
The humming sound is artificial. An EV is virtually silent if it’s driving slowly. This created a marked increases in slow speed pedestrian accidents, particularly when crossing blind alleys. Granted this could also be solved by people just paying attention when they cross the street but humans had generally gotten used to hearing some sound from an engine idling when a car was close. So they are now required to add a soft humming that plays whenever they are below a certain speed. Once you’re going more than like 20mph, the tires make enough sound that it’s not needed.
Interesting to me to note that different brands can make different sounds as long as they are loud enough to meet the guidelines. Companies now try to design these sounds as sonic branding. Covered in several episodes of the Twenty Thousand Hertz podcast. Www.20k.org.
Hyundai Ev’s sound like they are full of sad wailing ghosts when they are reversing. Spooky.
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