Basically, Ferrari will extract sounds from electric motors and various drivetrain components, measuring the resonance frequencies of the motor, transmission, differential, and even the wheels, before amplifying these sounds with a resonator setup to create a sound that correlates with the electric motor’s rotational speed.
It essentially boils down to the electric motor’s control system adding a so-called “sonority current” to the electric motor’s power supply at such a frequency that it won’t interfere with the motor’s operation. The sonority current is variable because it’s controlled by the motor’s control system, meaning that different frequencies can be created.
This sonority current will create a distinct harmonic frequency, or hum, in the motor housing, corresponding to the motor’s rotational speed. This hum can then be amplified by a resonator on the motor or its transmission housing to create a genuine powertrain noise.