What voice actually is
Author voice is not a single thing. It is the accumulated effect of every choice you make that is not strictly required by the story: the length and rhythm of your sentences, the words you prefer and the ones you avoid, your attitude toward the events you are narrating, and what you consistently choose to notice and describe. A writer with a strong voice sounds like themselves even when the subject is new. That consistency comes not from a particular style decision but from a settled sensibility that shows up across everything you write.