" 'Use my inside voice?' Why would I even have a inside voice?"
- Laugh Out Loud Cats #2288 by Adam Koford
When most people think of inside- and outside-voices, they're referring to volume, inside-voices are quieter and outside-voices are louder.
I don't get much louder than my normal speaking voice, so I have little access to the kind of volume normally associated with an outside-voice. So for myself, outside becomes equivalent to aloud, and inside refers to inside my head.
I don't know what it is, but I can't really yell or scream. I can project well so that I'm heard (in most settings) but significantly increasing my voice in volume is beyond me.
I suppose you could say I reduce the concept by an order of magnitude.