I had an interesting experience a few months ago. I seem to be incorrectly remembering it as percussive tinnitus - all I can find now is pulsatile tinnitus. Whatever it's called, it was a tapping in my ear at about 120 bps, only noticeable when going to sleep. It was possibly caused by a bike fall, very jarring to the body, no head contact, and disappeared after two or three weeks.