Do you ever hear things when you're very tired?

When I’m very tired, sometimes I hear very loud, strange noises in my head. Usually it’s gibberish or random sounds, but a lot of it is voices. Sometimes it even sounds like they’re shouting. One particular one that I hear often is a deep, threatening male voice.

When I was little, I called them “demon noises.” Now I believe it’s auditory hallucinations. Even so, it’s kind of frightening. I know visual hallucinations are pretty common when you’re very tired. I’ve heard of a study in sleep deprivation where people started seeing ants and spiders everywhere. Once I was at work early in the morning, and I started nodding off over my paperwork. Each time I fell asleep, I had a tiny little mini-dream that lasted around 30 seconds or less. They were all pretty striking, nifty images.

The weird sounds: have you experienced this, or heard of it? Would this freak you out?