Voices are far more common than people mention. most of the time they are unnoticed, they are the intrusive thought that thinks unacceptable things, just because our brains run a lot of options. if those thoughts, usually the self critical ones, leak into the conscious mind they can sometimes do so with a different voice aspect. a recent study indicated that a faulty gene in some people can lead to a feedback in part of the brain which routes thought through the aural network, resulting in them being heard, usually on the left side. People seem to equate hearing voices with split personality, which more often than not is simply not the case. often the voice is part of their own subconscious mind trying to send a message or trying to protect the person. sadly the way it comes across is often faulty. for instance If you have an aggressive voice telling you not to trust people and to hide away it can lead to isolation, depression and worse. when in fact the root of the voice is an insecurity and low self esteem problem which is triggered by social interaction. To stop you from feeling bad the voice tells you people are bad so that you avoid feeling bad about yourself. Sadly it doesnt work.

I'm a Psychiatric Nurse by profession and have worked with many people over the years who have heard voices. I don't like the labels psychiatry uses to define peoples experiences and have always striven to understand and support the individual and their own experience. The voices heard are not always benevolent though sometimes described as kind, funny or flirtatious and many can be torturous and cruel in the extreme.
I do harbour the belief that in ancient societies people with these experiences may have been revered as shamans instead of shunned or feared and may well have been seen as the mouthpieces of the gods.
30 years in and I still don't pretend to know the answers about how and why these experiences exist but do agree that the brain and its complexities in function are yet to be fully understood.

When I was little, I used to think I was crazy (or not religious enough) when I didn't hear God answering my prayers. Possibly part of why I became so skeptical by 10 years old.

But regarding ESP, I knew someone who thought he heard his loved one call out his name one night, as her car was crashing several miles away. She died at approximately the same time he heard her voice in his head.

I'm not sure I believe that it would be some sort of ESP, but when you're thinking of someone, it often is during a time that is challenging or they're going through something life-changing anyway. It's easy to attach some sort of meaning to coincidences.

Most of the time they are just talking to themselves, or hearing white noise ?