Crepitation, I was raised to believe, is the crackling sound made by a log fire: the little pops and snaps that emerge from arboreal combustion. More generally it can be any crackling noise: for example the sound made when you rub your hair together beside your ear. Go on, try it. Medically it is a "dry, crackling sound or sensation, such as that produced by the grating of the ends of a fractured bone", which I suppose must be similar.
This latter meaning - of which I was, until today, ignorant - reminded me of The Waste Land and
And bones cast in a little low dry garret,
Rattled by the rat's foot only, year to year.
Which caused me to discover a hypertext of The Waste Land, meaning an internet version of it with built in notes. This a Good Thing. I have a battered old copy in which I scrupulously and in a Lilliputian hand transcribed every note from the a companion volume. While the notes don't seem to be quite complete I can still recommend it. It is here.
There is a third meaning of crepitation: "the sudden expulsion of an acrid fluid by some beetles as a means of self-defence".
There is a post on crepitation over at wordnik. They cite almost infinite usages, most of which seem to be from a "Special Report on Diseases of the Horse". One though is from a book I had never heard of called The Cardinal's Snuff Box. It goes:
The tiled roof just above his head resounded with a continual loud crepitation, as if a multitude of iron-shod elves were dancing on it.