I believe intelligence and fear are very close together. Guys who say they are not afraid of anything, they are stupid. They are silly to me. . . I am afraid of everything
The most sensitive frequencies are at the resonant frequencies of the auditory canal. In other words, the ear has shaped itself to naturally amplify certain bandwidth. And that corresponds to sounds in that bandwidth that were most important to our evolving ancestors to hear, in order to survive. And it doesn't match the human voice. It matches birdsong.