When people with mental illness or medical issues say they "hear voices" (or other auditory hallucinations) ... what do they typically hear?

Static.

No joke, but do you assume that they all hear the same thing?

No. I knew a woman who, when dehydrated, typically heard music (the Hallelujah Chorus, God Bless America, etc). I’ve known someone who had an important relationship with a person who turned out didn’t exist. I do not know (didn’t pry) if it was a false memory of if the person had a “live: relationship with this person (e.g. thought this person was real until proven otherwise, or did they create a memory of this person out of thin air). When I was a child (7–9 years old) when I was afraid at night (as from nightmares, say) I’d sometimes hear whispers or random words.

They hear voices and not always in their heads. The voice can appear to come from somewhere in the room for example. The voices may say nasty things or urge the hearer to do something they wouldn’t normally do. Having said that I think most people if not everyone has a narrative of sorts running though their head at times though you are normally hardly aware of it.

Oliver Sacks wrote a very interesting and easily read book called Hallucinations if you are interested. It covers hallucinations of all kinds including auditory.

There are many different ways to hear things, and there are many different types of hallucinations. I have experienced auditory hallucinations when my mental illness was not responding to the medicine I was taking. At times, I heard voices. The effect was exactly the same as hearing a real person. There was no difference. There were times I heard music, but it was a bit different. I knew it was in my head.

Some doctors label the way we talk to ourselves in our heads as hallucinations, but that’s bunk.

The real difficulty comes from what the voices are saying. The voices I heard were always kind and reassuring. I have friends who hear truly horrific things. It can be quite frightening.

I haven’t heard voices in more than 10 years.

I did not fully answer how hearing things affects the person.

It really depends on the content of the hallucination. Frightening content causes great distress to the hearer. It’s truly horrible to hear some of the grotesque things that can be heard. It causes terror.

My hallucinations were not of that type. They were most often completely benign. Sometimes they told be happy things. Other times they were nonsense.

Auditory hallucinations are much more common than visual hallucinations (despite what Hollywood would have you believe). I think it’s common for people suffering from schizophrenia with auditory hallucinations to hear the voices of people. They literally can’t tell them apart from reality, it is real for them.

A part of an abnormal psychology class, I shadowed my professor, a doctor at a state mental health facility, for a day. I sat in on the delusions and hallucinations group session. It was incredibly sad. These are good people with feelings (like fear, and sadness) who are experiencing a reality that is different from actual reality. Imagine how horrifying that would feel.

The auditory hallucinations I used to hear when I was a teenager were very similar to thinking about the subject and the answer “occurs” in the mind. It seemed to be an outside source “telling” me the answer to questions at school and giving advice on how to act in some cases. It was always helpful advice.

My brother was a diagnosed schizophrenic and he said the voices he heard were actual people talking to him through an invisible speaker. He also said he often lived in more than one place at a time, and could be sitting in one place and walking in another at the same time. He said I only lived in one of those places.

They hear different things, depending in the culture they live and and its perception of schizophrenia.
While people on the West often hear insulting, verbally abusive, threatening things, people in India, for example, report on hearing pleasant and flattering things. That is because, while hearing voices is in Western civilizations seen as lunacy and is often negatively perceived, in India it’s explained as getting messages from deceased ones, usually family members, and is much more positively accepted.
At least that’s what I read in a Crack article.

So I suppose the fact that people wo experience such hallucinations ‘believe’ them (accept their reality and it even ‘controls’ them is part of the malaise

@Yellowdog The word “accept” implies some degree of choice. As I understand it, it simply IS their experience. There’s a subtle but significant difference.

For a color blind person that flower really IS grey to them. Imagine if you “heard” dogs talking to you. Sure that’s crazy nobody can talk to dogs, but if it was your experience then it could be a natural conclusion that you had a superpower that nobody else had. Sure you can learn that you have a condition that causes you to experience hallucinations, but remember your default experience is contradicting everything that you’re being told. Another way to think about it is if you’ve had a really vivid dream. Sometimes you don’t realize you’re dreaming and it feels very real even though those “experiences” don’t correspond with reality.

The crucial difference is whether you experience the voices as hallucinations, however real they seem, or as some outside agency communicating with you.

Tinnitus.