I'm mastering an audiobook for ACX and I need to ensure the final mp3 files have an average RMS betweem -18 and -23dB. Having worked more in metal where LOUDER IS BETTER (even though it's not always) I'm having trouble nailing this. Right now I'm dropping the mixdowns into Audacity and checking things there. It's a pain in the ***, and I have no idea how accurate it is.
So: Is there a way of measuring a file's average RMS? Can I get that number after the plugins (EQ/compression/limiting) on the master output, or do I have to do a mixdown and then get the file's stats.
Any help would be appreciated.