I recall certian parts about "The Art Of Kiai" in a recent book I read "Secrets Of The Samaurai" Also I have a real story at the end. Forgive the lengthy post.
"Kiai" is a compound of Ki and Ai.
Ki meaning mind and Ai the contraction of the verb awasu, signifying "to unite", As this combination suggests, it denotes a condition in which two mindes are united into one in such a manner that the stronger controls the weaker.
There is a certian legend regarding a samurai who was walking through the woods. He was surrounded with wolves. But he kept walking so aware, stable and potentialy explosive that the wolves were frozen with fear.
Other episodes recall men lying in ambush only to confront a victim who, simply by gazing at them, terrorized then so effectively that they were immobolized.
So there is an art of Kiai, but very little is known about it.
One real life expample of Ki that I can think of is my own masters story.
One day master was in the market with his grandfater holding his grandfathers hand and in the other hand his cane.
(the grandfather was very well known respected grandmaster martial artist may I add)
there was a comotion. It seemed a man stole a television set and was trying to run away from the shop keeper.
Since this was in the 60s he realized that the television was too big and heavy to make it. So he had to put it down to get away.
However he did not go far. The shop keeper caught up to the television and started to look at it to make sure it was ok.
The theif came up behind the shop keeper and pulled out a knife. The shop keeper was unaware of the thief behind him.
Just before the theif could stab him my master said that he could feel his grandfathers hand tighen around his hand.
And then his grandfather let out a Ki.
Everyone froze. The theif stoped and put away his knife and left immediatly.