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Inductors do this as well. The changing magnetic field causes the windings to vibrate, creating an audible sound. The sound my work monitor makes sounds like an inductor to me.



Right--or more commonly the cores of old power transformers will softly buzz at 60 hz.


You'll find it a lot in switching DC-DC converters as well. The pass inductors that help filter out the switching frequency can make quite a bit of noise, especially at higher loads.


My dimmable touch lamp makes an annoying high-pitched sound that is loudest on the dimmest mode. I searched for an explanation and apparently some light bulbs have filaments that are flimsy or light-weight enough that they vibrate audibly.


The power supply on the old Apple II "chirped" when switched off. I always understood it to be the oscillator decaying down from 20 KHz to DC in half a second or so.




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