Audacity peaks, Mac os, ACX lab

I keep getting this msg when testing on ACX lab "Peaks exceed 0 dB. Reduce peaks to below -3 dB. " I don’t seem to be able to resolve this through Limiter. I’ve tried numerous settings. And should I normalize or do anything else after Limiter? Thanks! This is very frustrating.

You may be missing a bunch of tools .

We authored ACX-Check which tests a lot of the same things that ACX-Lab does, but we also test for noise. Last I looked, they don’t do that.

Follow that with Audacity Audiobook Mastering which guarantees Peak and RMS (loudness) in one step.

We made it a point to test for noise because that kills more readers than anything else.

Also note, none of this tests for theatrical quality. That’s what killed me. I produced a practically perfect in every way sound file, but failed mouth noises.

Homes are too noisy, or have too many echoes for good quality sound production. And that’s nothing compared to fighting with your computer insisting on “helping” you with your sound quality.


Also note, we don’t exactly follow the ACX published standards. We strongly recommend -65dB background noise (or quieter) rather than trying to hit -60dB exactly.

Also Mastering produces peaks at -3.5dB (quieter) rather than the published -3dB.

When you create your MP3 submission, the standards may slide around a little bit—MP3 is a compressed and manipulated technology—and it’s good to account for that.

You are making an Edit Master WAV file of your chapters, right? Once you make the submitted MP3, you can’t open it up and correct something without messing up the compression quality. Correct the WAV Edit Master and make a whole new MP3.


You can submit a short sound file to the forum. Sometimes we can catch errors before you go through the whole ACX submission dance.


Check there is No “make-up gain” on the limiter.

Voila! I had read in several places that I needed to have Limiter hard limit for voice narration, but on your recommendation I changed to soft and it passed muster! Thank you!!

This topic was automatically closed after 30 days. New replies are no longer allowed.