They turn off over ~18MPH, though. After that, tire noise is much louder. As loud as an ICE car.
So, realistically, you’d hear a Prius if it’s going normal road speeds.
Side note: I wish the sound was more pleasant. When multiple cars are moving in a lot I call it the “choir of the damned”. They’re also louder than ICE cars and that’s kinda lame, we moved backwards WRT noise.