The author’s voice, the narrative voice that delivers the information, is a kind of extra character.
Examples of "voice":
She was not a forensic expert, but it appeared that the laser-beam had penetrated his body from behind.
She was no expert on this stuff, but it looked like he got blasted from the back.
We read stories written in many different voices: eloquent, casual, sassy, hip, melancholy, cynical, and so forth.
Different stories may call for a different narrative voice. The voice I aimed for with my first novel was, “A good story, plainly told.” Also, “Spare, vivid prose.” I kept both those notes on my computer.
Don’t worry about “finding your voice.” Just tell the truth, as you experience it. Write like you talk.
The same is true for “style.” It emerges naturally, like an apple from an apple tree. You don’t have to do anything to force it.