This thema is super interesting! I myself also hear a voice, depending on the characters I'm reading and I see the szene in my inner eye. But it is sometimes annoying, especially, when it's time to sleep and my inner monologue starts kicking in xD
Recently I watched a video from Nina Fleer, a german artist talking about hyperphantasie. It is sadly not aviable with english translations. There she has different tests, on how good you can imagine an aple as example. Can you see the shape? can you even see colors? etc.
Interesting thing is, there are people, who even can imagine the taste or textures of things o.o I myself can't but my partner was shaking, when he had to think about the sour taste of a lemon. It's so wild
Here the video: