One of the most unique parts of going to a Formula E race is the sound—or lack thereof. Everyone I’ve met who routinely works along the pit lane, for example, has some horror story about almost getting run over by a nearly silent car. At speed, though, there’s some odd future-spaceship whine sound that comes from the cars.

You can hear a bit of it coming from this quick video of the Robin Frijns’ Andretti car setting off from its garage. It’s a high-pitched assortment of squeaks and whines.

We asked a member of the Mahindra Racing team what actually makes sounds on these cars, and according to him, the high-pitched whine at speed is primarily coming from the gearbox. Racing transmissions use that whine a bit, as they don’t have to worry about being quiet. In Formula E’s case, it’s one of the only sounds the car emits The gearbox has to feed into a mechanical differential, per the regulations, which no doubt adds to the sound.

That’s an item that’s now open for teams to develop as they wish, with some teams running only one gear. Mahindra has two. Others have three gears. and the original-spec Formula E car I’ll get to drive later has five. The rationale varies from team to team, but it’s often used to optimize how the car uses its power on track—just like any other race car’s gearbox, really.

The other noise, obviously, is the tires. They’re harder than most race tires and squeal like a little piggy when they slide and drift around turns.

So, now you know: that whine is all gears, for the most part. I expected it to be more of a crazy electric whine, but nope! The cars are nearly silent at lower speeds, and the real reason for that whine is a lot more low-tech than I would have expected.