Help me with RMS levels and mastering for ACX

RMS means Root Mean Square or the area under the curve, which in audio is interesting to derive because of complex waveforms between 20Hz and 20000Hz. It also happens to correspond to loudness.

So when people tell you to set your RMS, they’re really complaining about loudness. ACX has very specific restrictions on loudness variations, -18dB to -23dB. 6dB is not that great a loudness variation and as long as you’re inside of that range, chapter to chapter variation should not be a problem.

Until relatively recently, we had no good way to directly set RMS. Now we do and the mastering process, assuming you get close at the microphone can shrink to a sentence or two.

Every time I write a Mastering Tutorial, something happens and I have to start over. This was the last pass.

You’re good all through Comments

Custom Tools changed. We are now using RMS Normalize with a setting of 20dB (it defaults to 18) in place of SetRMS. You need to be on Audacity 2.1.3 or later!!

Use the first three sentences in Process subbing RMS Normalize (20) for SetRMS.

If you have noise, that’s when the process falls to pieces. There’s different pathways depending on what your noise is.

I will eventually fix that publication…

Oh, sorry. Process chapter at a time. The new tools should keep you inside ACX conformance.

But the really bad news is the need to start with a raw reading. We can’t take effects and corrections out, so going back and fixing a badly processed reading is rough/sometimes impossible. We strongly recommend exporting your raw readings as WAV (Microsoft) 16-bit before you go on.