Not only does the modern person often think that sight is more important than sound - there's no objective evidence to indicate that. Many people, even audiologists who study the science of human speech and hearing, have assumed for a long time that the human ear evolved to hear the human voice, rather than the voice changing to fit the human ear. And the human ear is actually not a perfect match if we map its sensitivity to the different frequencies in the human range of hearing; it's an unequal curve, it's kind of a wavy line.