noise between 70 and 90km/h

Hello there,
I've had a strange noise coming from the front of the car for a few weeks.
It's a kind of rumbling noise coming from the front of the car.
You can hear it from 70km/h (45mph), you hear it the most at 88km/h (55mph), and you don't hear it at all from 90km/h (56mph).
The noise comes from the engine, but it's not related to the combustion engine: when I accelerate hard, the noise is always the same, you just hear the combustion engine over it.
2 people listened to it: the first said it sounded like something rotating, the second said it must be a noise coming from the electric motor.
It doesn't seem to be linked to the front axle, as you can't hear it all the time.

Does this sound remind you of anything?

Thanks for your help!