I am sure all of us have told a child, whether ours or someone else’s, to use their “inside voice” when they get too loud. If we haven’t used it ourselves, we have, at least, heard someone else use it.
What I have found is that, as I get older, I need to remind myself to use my “inside my head voice.” I have always talked to myself, I think we all do, but at least I kept it inside my head. Now I catch myself talking to myself out load. It generates interesting, and occasionally understanding, looks.
If you are like me, rest assured that you are not alone. If you don’t do this, and witness someone who does, be patient with them. You may be doing the same thing someday!