NO ANSWER WILL BE SATISFYING

Have you ever had this happen to you? You're just hanging out, being you, minding your own business, when all of a sudden a weird ultrasound whine starts up in one of your ears?

What in the hell is the cause of that?

I refuse to believe there's something in my ear that's capable of vibrating at 2 kHz or whatever that frequency is. It's got to be something else. But first I need to know if I'm crazy or what.