為什麼有時聽音樂時會起雞皮?

we can react to stimulus. in the case of listening music,
the sound wave will be received and transmitted to our brain.
then our brain will give out some responses. for good music,
we may be pleased. for loud noise, we will be angry.
for high frequency of sound, our skin may have some
雞皮, after the sound is over, it will disappear also.