Noise Floor

Every room and every microphone contributes a background level: air conditioning, a fridge two rooms away, traffic, the preamp's own hiss. The noise floor is that level, and what matters is the gap between it and your voice.

Record 30 seconds of the empty room before you start. If the gap is wide, light cleanup will do. If it is narrow, no plugin will save the take, because noise reduction works by removing what is there and takes some of your voice with it.