M.J.
What I've done with my daughter, 21 months, is I whisper to her. I'll whisper songs, poems, secrets. She mimicks me and sometimes will whisper back. It's taught her different volumes when speaking.
Maybe try the indoor voice, outdoor voice game. Set time aside for loud voices and time for quiet voices. If my daughter screams and throws fits in anger, I give her momentary time outs in her bed. She'll cry it out in anger but after maybe 2 minutes have passed, I'll get her up and instruct her to use her words.
Other times when she yells, I bend down face to face and ask her to use her words. Tell Mama! Then I suggest words to use like: Do you want up? Do you want a drink? Is it stuck? Do you want Mama to fix it? Usually once I've hit the nail on the head, she'll repeat back the thing she was trying to express. Yelling out of anger or frustration is usually them just getting upset from not being able to express themselves.
Good luck.