Not the person you're responding to, but yeah, the voice-in-my-head CAN (but does not always) sound just like actually hearing someone.

I have a caveat there because the "voice" that is "me" (that is to say, I don't perceive it as someone else talking, but me talking/thinking to myself--it does not have the feeling of an outsider or stranger talking to me) does not always hold all the "information" of an actual audio voice.

Like, I don't normally carry the same "pitch" as my real-life voice, it's usually without pitch, but can still contain emotional prosody? It's a shifting mix of soundless but verbal (as opposed to nonverbal) thought and sound-markers that indicate emotion in real life when spoken out loud.

However, I'm also a writer, and when I write dialogue of a character, it usually carries "sound information" much more distinctly in my head, like listening to a radio narrator or watching an actor. Like, a male character will have a lower voice, a female higher. A flamboyant character might pronounce and say things with a lot of drama and theatrics, where a stoic bored character might be closer to a monotone. It's all controlled by me, by the way--it's not schizophrenia where I perceive it as an outside person or force talking to me. But it is very "audible". (But there's still some mental filter where I know it's thought and don't mistake it for real in-the-present sound.)

...I did have musical training as a child which might play into my ability to have strongly imagined sound in my head. When I get songs stuck in my head, I actually do "hear" them. I hear the singer singing, but also the unique tones of the various instruments. So if a song has a guitar I hear that, but if it's a piano I hear a piano playing it in my memory and not a guitar.

...these things don't always have 100% fidelity though, it's not like playing a file on a computer. It's a fuzzy in-and-out-of-focus thing. But when it's "in focus" it's definitely something tagged by my mind as "sound".