http://en.wikipedia.org/wiki/Tensor_tympani_muscle
Here's an odd bit of anatomy: a muscle in the middle ear that some people can flex at will, and that makes a booming/rumbling sound in the head. I've been able to use it for as long as I can remember; it's my own personal bassbin.
Who else here is similarly 'talented'? Curious to see if it's common among psy/goa heads...