Do you have WAV copies of all your raw readings? No filters, no effects, no corrections. Just as you read them. That’s highly recommended. Keep it/them in safe place, divorced from all your editing and production. It’s a New User error to announce directly into an edit session and then on to the finished production. If Audacity or the computer goes into the bin anywhere in the process, it can take the show and all the work with it sending you straight back to announcing into a microphone in a quiet room.
ACX requires submission as MP3 compressed sound file chapters with at least 192KB quality. You need to know that if you make a mistake in the submission, you can’t correct the MP3, reexport, and resubmit. Every time you make a new MP3 from an old one, the quality goes down. The new one isn’t 192 any more. You have to edit your perfect quality WAV Edit Master and make a new MP3. That’s why a WAV Edit Master is a terrific idea.
Audio Lab does not detect issues such as noise floor or editing errors
Correct. I think I mentioned that. They check everything a machine can check. Noise is hard.
ACX uses RMS - Root Mean Square as the loudness standard. It’s a math function. It’s the area under the curve or the amount of “energy” in the chapter. I don’t know of different ways to detect RMS.
Some production companies use LUFS instead of RMS. That one can determine loudness, too, but it takes into consideration the odd things your ear does when it hears things. For one example, your ear doesn’t work very well in very high and very low pitch sounds. LUFS knows this. RMS doesn’t.
A word on how Audiobook Mastering works. There are some tricks to it. We are cautioned sternly to apply the three Mastering tools one after the other (or apply the one-step Macro version. Same thing). Do not add any tools or leave any out.
Filter Curve, the first tool is a rumble filter. It gets rid of thunder, earthquakes, heavy trucks going by, and some thumping breath and wind noises . It pre-conditions the chapter for the next tool, Loudness Normalization. That’s RMS. There was a recent poster who set that for LUFS by accident instead of RMS and started getting odd chapters. Yes. You would. RMS Normalization cranks the overall volume of the whole chapter up and down until the “energy” or loudness is perfect. The chapter goes on to the Soft Limiter which gently folds the tips, peaks, and high points over until they pass the ACX peak specification.
I bet you’re wondering to yourself why doesn’t the limiter affect RMS. It does, but not much. Compared to the massive, ground-shaking work RMS is going, changing a light, delicate tip or peak here and there is a piffle.
Please note that the chapter before Mastering and after is significantly different. “After” doesn’t have thunder and earthquakes. Those two can have very serious energy issues as anybody that has every been through an earthquake can tell you. Weirded yet, you can’t always hear them.
That’s why a similar rumble filter is found on most outside broadcast sound mixers, field sound mixers, or recorders.
And that’s why if you submitted before and after mastering to ACX for testing, it may be different. ACX Check will be too.
Koz