Help me with RMS levels and mastering for ACX

I know it’s tempting to pay surgical attention to the position of the knobs, but they’re almost irrelevant unless they run all the way up or down. Your goal is to make the Audacity volume meters work out perfect or nearly perfect.

Yes. I applied two different tools to get what I got, one built-in to Audacity and the other custom. You can get custom RMS Normalize from here.

After I got the performance to pass, I found I could do even better with the rumble filter LF Rolloff for Speech.

I did write a Mastering paper. It’s supposed to be on Revision 2 by now, but I haven’t gotten to it.

The top part of that, Notes and Comments is still valid. Read through that.

The second panel Custom Tools you can use to find and install LF-Rolloff. You don’t need the other two, You already have ACX Check and SetRMS is obsolete.

The third panel Process is almost a lost cause. The old RMS tool was almost raw programming and had to be applied by hand. My joke is that it was written on a paper napkin with felt-tip pen over burgers and it’s been used that way ever since. The replacement is RMS Normalize and it’s an actual finished tool.


You need to make sure whatever you produce for correction has at least 3/4 second of shut up and don’t move Room Tone. Noise analysis will fail if you don’t do that and it can’t find enough silence to chew on. I think something like that is built into the ACX submission standards.

Effect > RMS Normalize: Set the target to -20dB. > OK.

(The blue waves may look funny here. That’s OK)

Effect > Limiter: Soft Limit, 0, 0, -3.5, 10, No. > OK.

Analyze > ACX Check.

You can suppress the small rumble sounds and do better with noise.

Effect > Equalization: LF-rolloff for speech, Length of Filter around 5000. Not critical. > OK.

Analyze > ACX Check.

I expect that to pass like it did here.

Note we didn’t need Noise Reduction. Noise Reduction can be dangerous. ACX has a failure called “overprocessing.” If they can hear you messing with the sound, they will bounce you.

So that’s the basic setup. You still have to read evenly. There is no compressor or any other way to correct for that segment in the middle where you doubled your reading volume by accident.

If the voice theatrical quality seems right to you, it’s out the door — break for coffee.

Do you have the ACX submission standards?