Quote (Touhou @ 14 Apr 2014 18:55)
Now, if you're referring to the excitement of the vocals with the comparison of being tortured, I think I may have an answer.
During the anticipation of the action, the epiglottis portion of the larynx becomes enlarged due to the excitement and enlargement of the diaphragm. So the two share the same trigger of growing which causes the sound waves to create a higher frequency, notably, when you're hearing them yell/scream "eyahhh." Because of the said enlargement of the larynx, the high pitch sound waves are obviously existing with the smaller pathway of exit. For males, we have a larger escape which is why ours isn't as high pitched in the adult stages.
The voice actors are well aware of this phenomenon, and undergo special torture and pleasures to mimic this skill perfectly.
The activity in the Broca's area of the brain control this concept and the physiologic reactions in the brain cells are quite similar. When the signals of the neurotransmitters from the brain react to the situation, it's practically the same sound in which people perceive such as the OP.
In a shorter version.
Girl crys, tells the guy to stop, it hurts!
2 minutes later : IKUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU~~~~~