Yup, 3-4 months was when my voice changes became noticeable and obvious to others. I had another drop in the 6-8 month window, then again at about a year. Roughly 2.5 years on T, I think my voice is done with any major changes, but it's continued to mature in some ways (as everyone's voices do with age, cis or trans). Thankfully it didn't take very long for me to leave the squeaky teenager stage.