What is causing a ticking noise in my electrical outlets?
Here are some possible scenarios:

True story: I was called out to troubleshoot a chirping outlet.  My first thought was just a bad GFCI outlet.  To my surprise the outlet was indeed chirping and not a GFCI.  The source was 5 computers, monitors, and other electronic devices all daisy chained off one outlet that had become loose or was never tighten good.

Electronic devices will "chop" up the electricity, some worse than others.  And apparently can become audible with the right conditions.

Easy fix: just tighten the screws on the outlet or replace the outlet all together as it may be defective.

Also keep on mind some GFCI outlets will make a buzzing noise, and sometimes but rarely will chirp very loudly due to the internal parts failing.