Delete comment from: Ken Shirriff's blog

Atlant said...

With regard to "what mechanisms create audible noise", besides electromagnetically-driven motion of the wires, magnetostriction is also very important effect.

http://en.wikipedia.org/wiki/Magnetostriction

This is the property where a magnetic material (such as the transformer's ferrite core) actually changes size as the magnetic field changes. This effect is unavoidable and is often the principal way that transformers create acoustic noise. The only thing you can do is try to keep the noise from coupling to other materials nearby.

May 21, 2012, 8:00:01 AM

Posted to Apple iPhone charger teardown: quality in a tiny expensive package