Listen, I am talking to myself.
Humans usually crave the company of other humans. They like to talk to each other. When women talk to women, they look each other in the eyes; men tend to avert their eyes from the faces of those with whom they converse, but thy still wish to converse, to hear the sound of their voices, and to patiently wait until the other person has finished talking before making their point, which is usually no more than what they said before, but with different words.
When someone makes a point that is a good point, the person tends to repeat it, as though the idea is worth repetition, just in case the listener has not heard it properly or understood it.
When a person is alone then speaking out loud, so you hear yourself, is a comfort. Reciting out loud a poem or singing a song is a different comfort, because in doing these things, even if it is merely humming a tune, is in essence a conversation with a person who is not with you. Thus you can converse with Shakespeare, Beethoven, Leonard Cohen, John Lennon or whoever you first conversed with, when you were young or when you were in middle age, or when you were old.
This human desire, to speak and to hear oneself speak, is what keeps some sane, because sanity is partly the feeling of being loved and partly the feeling of loving oneself.