About two weeks ago, I came home and noticed a piercing high-pitched noise in my room. After searching for the source of this noise, I found it was coming from my PC's power supply unit.
Later that day, my sister pointed out that the microwave was making "strange noises." I checked, and it's the same noise that's been coming from my PC.
This noise is intermittent, as the noise on both appliances will occasionally stop. It's only been happening these past few weeks and I'm at a loss as to how or why this is happening.
Is this normal? Can anyone explain why this happens?