There is a high-pitched noise coming from my bathroom exhaust fan. The noise squeals like air escaping from a balloon, it is high-pitched and mimics built-up pressure being released. It happens sporadically throughout the day and how long it lasts is also sporadic. There is no rhyme or reason for the timing of the noise. It is not electrical, as this happens while the unit is unplugged and when it is switched off.
I have a video that I recorded that will describe the noise better. If you care to see/ hear it, I can send it in a reply email or text.