Every character should have a unique voice. And by that, I don’t just mean speech patterns, words, attitudes, and so on, I also mean physical voices. For instance, are they high, low, nasal, etc.?
I used to describe what my characters’ voices sounded like in my earlier writing days. And in my book, The Frights of Fiji, I do say what a few characters’ voices sound like. Two of them are described with deep voices and one is said to have a high voice. However, those were mainly done for comedic purposes. I originally published The Frights of Fiji in 2013 as From Frights to Flaws. I now refrain from explaining how my characters’ voices sound, unless it’s important to the stories.
Even my main character’s voice noise isn’t revealed. In the sequel, there is a scene where she sings a certain song. Although I state that she takes chorus at school, I don’t specify if she is an alto or soprano. That is because I want readers to use their envisions to what her voice sounds like.
Many people dislike when characters’ physical appearances are described unless they’re important, otherwise, the readers should get to picture them their ways. I happen to be the opposite with that. I am an advocate for authors to describe their characters with whatever traits they want, as long as it’s not too many (since that can bog down the narrative and be too much to remember), or offensive. I not only believe that writers deserve the right to physically describe their characters, but I also cannot picture characters clearly unless the narrators say what they look like.
That being said, it’s the reverse for voices. Since I first wrote Book 1 of my “Magical Missions" series, I learned more about the writing craft, and chose to give up with explaining how characters’ voices sound, except when it’s crucial. I would recommend that to all aspiring writers. A few voice sounds revealed here and there probably won’t matter. Just be sure not to overdo it, or else, it might overwhelm your readers.