You could try what helped me: i never ever heard my sons yelling screaming arguing, and this is how I achieved it.
When my son started getting a little louder than I'd prefer him to talk, I sat down, pulled him gently to my side, held his hands softly in mine, looked deep straight into his eyes, and WHISPERED HIM: "Anton, I do not hear you, u=you speak too loudly! Please say it quietly, i want to hear what you say!" And he whispered me back what he was about to yell out...
there are several things in action, as you see, with such a move:
1. you give a loving touch, affirming him that the place is secure and safe with you;
2. you make a DEEP eye contact, assuring him that ou are totally receiving what she wants to communicate to you, that you are totally ingterested in this communication between you two
3. you give a logical background to the need of this change of the volume, which is important as children do think logically, from a very early age, and when they undrestand WHY, they are most likely to follow your advice.
4. you WHISPER, inviting and showing by example, HOW you want you two to communicate. ids are monkeying so much, they like repeating what others do, so it is easier for them to follow your advice when they see the example on HOW to do it
5. and lastly, you need to follow through! Once you start practicing this 'trick', (if you will), you need to ALWAYS NOT HEAR what she says too loudly. ALWAYS sit down, repeat the exercise of holding hands, seeing dewep into eyes, and whispering your wish to understand what she tries to say too loudly.
you can add to the fun, saying that you see her lips moving, you see she wants to say something, but it is too loud for your ears, and you just do not hear this voice, you need it softer, and quieter...
GOOD LUCK!
yes, and do not say it won't work because it is too simple, unless you TRY!
Try it, please, is my advice!
All the best, and be happy, you both ;) !
M.