Why Do Some AC Adapters Make A Noise?

Today my girlfriend was worried about the power adapter for our grow light making noise. She worries a lot about electrical things. Next thing I realized after I told her it was okay to use it until we get a new one that doesn’t annoy her and I thought I would post it here.

Once in a while we notice if something is making a noise. I don’t personally hear it but my hearing isn’t great.

The reason why they can make a noise that the adapters usually have a transformer or an inductor in it. They’re basically a coil of wire that uses magnetism to convert the high voltage power coming into it to a lower voltage that’s usable for the device. The magnetic field is varying and on cheaper power supplies it can cause the coil it self to vibrate. The physical vibration make sound waves which is what you can here.

I don’t really remember where I learned this. Maybe back when I was a kid I read about it somewhere when I was trying to learn electronics.