Cheap electronics, particularly with switch mode power supplies can be pretty bad for magnetostriction in transformers/inductors or piezoelectric effect in capa

Cheap electronics, particularly with switch mode power supplies can be pretty bad for magnetostriction in transformers/inductors or piezoelectric effect in capacitors leading to these high pitched noises. When optimising for the cheapest borderline in spec components to get the bill of materials down this is even more likely. When these noises are present they can be extremely difficult to track down where they are coming from in a room