A mysterious phenomenon.

The air conditioner in my office is horribly loud, but I only notice when it cycles off. It goes off and I realize that I couldn't stand it. But if I couldn't stand it, why didn't I notice when it was on? And I also have the feeling that time reverses a bit: I seem to start hearing the noise a split second before it goes off. And I don't mean just once. I mean every time, thousands of times. I become aware of the noise and then it goes off. That's an illusion, of course, but I've experienced it so often that I know it's a very specific phenomenon, and I wonder how many other things there are that we perceive out of order like that.