Why can some Xiaomi Notebook Air 12.5 inches hear the sound of electric current when it is quiet?

Solution:
This is the sound of the capacitance and inductance of the power supply circuit required by the intel core m series cpu . Due to individual differences, some machines have sound, but the sound is very small, far below the noise control standards of Xiaomi and the country. And the noise will not increase with the use of time, please rest assured to use.