When it comes to the loudness of your audio stuff, please don’t use old good RMS anymore. They are outdated these days.
Use LUFS instead. It’s a way more accurate unit to measure your loudness.
Still, at the moment (November, 2018) one of the biggest platforms on the audiobook market — Audible/ACX, uses RMS and doesn’t care… The thing is that in some cases (please see video below) RMS may let you down and eventually it’s being reflected on your user/listener’s experience.
So, simply be aware of this fact during the mastering for ACX.
As usual, if you need an advice or assessment, or you want me to prepare your audiobook for publishing, please don’t hesitate to contact me!
Always work with those you want to hug ツ