The ears can hear two kinds of voice ,one is the sound ,another is the noise,but they are two completely different factor,when you heard about the voice ,i.e music,languages,you might few this is a way of imput.The noise,on the other hand ,you might feel the ear is doing a project of output and never felt well.
However,the noise in recent years has been divided into two sections ,one is the achievable noise ,the other one is unachieveable noise.
这篇题目太大了,可以做调研了都