system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why Do Lights Hum?

I'm sitting in one of our study rooms and the lights are making a humming noise, any idea why this happens?
gpt
Some lights, like fluorescent tubes, require voltages different from those in regular wall power. To transform wall power into what is required for the bulbs something imaginatively called a "transformer" is used.

A transformer uses the fact that an electric current through a wire produces a magnetic field, and a magnetic field produces a current in a wire (induction). This is how electricity is made in a generator, by cranking magnets around near coils of wire. In a transformer one coil can be made to induce a current in another, but with differing numbers of coils the voltage can be changed. So we could increase the voltage for our bulbs with just two coils of wire wrapped around some chunks of iron.

Now if you recall the magnetic field used to transfer this current can be quite strong. Also it isn't steady, it switches back and forth (AC = alternating current). This switching creates physical stresses in the structure of the transformer, it is like a big magnetic hand trying to bend the coils this way and that. While the structure is strong enough to withstand such forces, it is bound to flex somewhat. That means quick, short vibrations which can often cause audible humming.