this isnt coming from any amount of professionalism, but i find that knowing how mouths create voices and accents helps a lot.
to describe, someone with a feminine voice often speaks that way because their throat is tighter than a man's typically is, causing a softer, more delicate sound (but not necessarily a higher pitched one). while a masculine one is more guttural (coming from the throat) and sounds rougher because of that. something else to understand is that most of the time voices arent actually as stereotypically gender specific as you might think, with plenty of variance between people regardless of what sex they are. it's fairly easy to recognise a female voice when you're in the presence of one, but when that voice becomes detached from the body (via recording or simply just not seeing the person) the sex of said person immediately can become very difficult to tell.
another thing to look into is describing each separate part of the voice, and breaking it down into it's components. think to yourself, what are the lips doing, what are the teeth doing, how are they interacting with their tongue, what volume are they speaking, what pitch is their voice, is it rough and coarse, or is it soft and slippery. what is their current attitude and mood and how does that affect the way they sound? do they have a particularly dominant accent, and if they don't, what connections might other people draw to other cultures? maybe they have a slight lisp when they pronounce their "r"s or "l"s, or maybe they have trouble with their "w"s. do they have a noticeable mannerism that could change people's perception of how their voice is? maybe they have a honeyed, silver tongue and are prone to lying their way out of things, and this is noticeable in how they speak. maybe they are are quick to judge and their voice sounds harsh and sudden, causing skittish people to be nervous in their presence. maybe they are sweet people and their voice sounds sweet as well.
try researching different accents from around the world and how they're produced, or maybe listen to celebreties or friends speak and try to think of the things they remind you of.
a personal favourite of mine is the "husky" voice. a voice that sounds rough and a little scratchy, but in a very seductive and attractive way. someone who is tired or just woke up might sound a bit husky. if youre sick you might also gain a bit of a husky voice. a husky voice typically has it's own strange smoothness to it, despite sounding low and a little gravelly. perhaps simply due to it's relaxed, calm nature.
