As soon as the power supply is switched on, a softly audible hum fills the listening room. But where does it actually come from?
I came across an interesting short article about this, which I would like to share with you.
At a typical AC frequency of 60 Hertz, a new magnetic field is built up in the iron core 120 times per second. Since magnetized ions strive to move closer together, the iron cores shrink. In a core with a diameter of one meter, this amounts to only one millionth of a meter. However, precisely this permanent rearrangement at an atomic level makes itself noticeable through the constant humming.
Cause of transformer hum -> Wissenschaft.de
Nevertheless, there are many different reasons why a transformer can hum particularly loudly. An asymmetrically wound transformer hums significantly louder than a symmetrically wound one, and much also depends on how the transformer is mounted. A mounting screw that is not tightened securely, unwanted housing contact, or severely contaminated current can be reasons why the transformer hums significantly louder than necessary.
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