I was wondering this same thing just the other day.

I don't really hear my own thoughts, only if I actively practice saying things inside my head. Thoughts are more like concepts, movements or 'senses' inside my head. Intrusions and conflicting opinions "move", kind of like a bulldozer it feels like, from different directions.

Occasionally I do hear sounds. Sometimes a phrase that maybe is a response? to what I'm doing. I hear it near my ear in my head.

Other times I experience something I call the crowded cafe in my head. It's in the background. I have no idea what this is yet, if it's like echos of people I heard talk that day or media I watched. It's not actual repetition of that but I don't know. Sometimes there seems to be some correlation, like watching a tv show in a certain language and then there being more of that language in the "inner cafe". But yeah, I experience it exactly as being in a crowded cafe and catching random snippets here and there. The snippets make absolutely zero sense to me. Sometimes it's like a word or a sound is on repeat.