Working with little kids, one actually teaches them which versions of their voice to use in which circumstances. Along with a hundred other things most people blow off as natural, that are actually learned. (From where to hold your eyebrows, to what your laugh sounds like, to whether your voice is pitched through your nose -Eastern Bloc people do this, it's part of why they "sound" snobby or arrogant to most English speakers, as we're taught to pitch our voice through our noses for emotional effect; whining, disdain, etc.-.). Kids everything is extremely mobile. (Facial expressions, voices, body language, etc.). A huge part of this teaching is monkey-see-monkey-do, but another piece is very much intentional. A lot of these things very much become "locked in" by a certain age.
The eyebrows thing, as an example? Americans hold their eyebrows 1/5th of an inch higher than Europeans. Those orbital muscles "set" fairly young. I can almost always spot people who moved to the US as older kids... Because even as teens... They have these 2.5 lines across their forehead that come from raising your eyebrows 1/5th of an inch, and holding them there 24/7. When most people's faces don't line until their 30's and 40's, because fractional expressions take infinitely longer to crease in than expressions held day in and day out. It's not a deliberate thing, it's an assimilation thing that only kids do, but that happened after their orbital muscles set as toddlers. It's also why facial reconstructions, from skulls, never really look like the person ... Unless you know what region they grew up in & what region(s) they lived in, even then it's not perfect, but it's a LOT closer. It not only changes the cast of the muscles, and other unconscious things, but also things like how much water-fat they have. There are some wicked cool computer programs that let you imput all that data, these days. Same skull, will look like very different people depending on culture & climate.
And, no, in the nature v nurture argument I'm hardly taking sides, just because so much is learned. Which lessons a child learns, and how? That part is very much nature. 2 kids from the same very loud family may each be polar opposites of each other, just because their personalities grabbed different parts of the lessons presented to them