There’s really only so much you can do to train small children to be quiet. My oldest is almost 4 and she’s just now getting to the point where she’s able to be quiet on her own for extended lengths of time. My younger kid is 18 months and when she’s awake there’s basically nothing that can stop her squawking.
We are moving to a house next month with a separate office space on the other side of a 2 car garage from the main house. I am beyond excited.