Normalizing for ACX parameters

I am using Audacity 2.1.0 on Windows 7. I’ve narrated several books now for ACX, all successfully meeting their parameters and by using the same procedure each time, which I learned through this wonderful forum. I record and edit, then Normalize to -3.0 dB (Removing DC offset). In the past when I did this it only affected my Contrast by .3 dB (e.g. -19.3 to -19.6), but now it’s lowering it by 3 dB (e.g. from -19.3 to -22.3).
I am really a novice and don’t even really know what these terms all mean, but I’m wondering if I accidentally hit something I shouldn’t have. Any suggestions?

My personal favorite is Normalize to -3.2, not -3.0. Volume peaks in your show can change slightly when you make the MP3 file. It’s just how MP3 works. Volume can go up slightly. If it does, you may violate the ACX peak volume standards which are exactly -3.0. Using -3.2 gives you a little breathing room.

It’s making my head hurt thinking of reasons this would happen.

Select the whole raw, unprocessed performance by clicking just above MUTE. Effect > Amplify, but do not apply the tool! Just read the top number and Cancel. What is that number?

My guess is you created at least one loud noise in the otherwise normal performance. It only takes one and it can be anything: tap the microphone with a pen by accident, bump the desk with your knee. Both Normalize and Amplify work on the loudest part of the show. That’s normally your voice, but anything in addition to that can mess up the tools. Did you sneeze?

What does the Amplify test say?

One of the reasons this process is a bit of a mystery is we use some tools not normally used for this task. Contrast, for one example, is normally a comparison tool (contrast these two sound clips) but just happens to deliver the performance loudness number that ACX requires.

Are you using the new ACX-Check tools? They’re a lot more convenient than messing with Contrast (although that still works).


Thanks, Koz.

When I do the Amplify test after Normalizing, it shows 3.0 and I always Cancel out of there. But you have given me something to consider when looking at the whole performance.

Occasionally the dialog calls for a yell or shout and as much as I try to get it across without getting too loud, maybe that is my problem. If so, how would you recommend I reduce the level on that particular section?

And I’m not using any ACX-Check tools. I don’t even know where/what they are, but they sound like something I should learn about.

I appreciate your help very much!

When I do the Amplify test after Normalizing, it shows 3.0

But if you do that to an older original raw recording, I bet it shows around 3.0 or very close to it. I also bet if you do that to your mystery raw recording, it’s much louder than that, say closer to 1 or even 0.5. That would account for Normalize reducing the overall volume by 3 instead of a more normal, tiny change.

a yell or shout

That would do it. Those can be done by actually getting loud, but backing away from the microphone or facing away. Depend on the theatrical stress in your voice to carry the meaning, not the volume change. I know actors who can do that with just their voice. You can use the Envelope Tool and zooming to reduce the volume of specific tiny portions of the show.

I think you can also get the new limiter tool to help here, too. Its job is to identify taller than normal (loud) blue waves and suppress them according to its settings. I’m going to be in high grass here, I’ve never used it.

ACX-Check tools

I recognize the original sound test tools I posted a while ago. I forgot about them. They still work, but ACX-Check is so much handier and faster.

The older tools required you to go back and forth between Amplify and Analyze > Contrast multiple times to see what you’re doing. Any time you have multiple repetitive actions like that, it calls out for a program to do it. Will consolidated several existing tools and programs into a single measuring tool that appears under the Analyze menu (attached-1).

I have the older one which is a little hard to read (attached-2) , but tells you the three values you were getting using the individual tools:

Peak Level (how close to overload damage are you)
RMS Level (how loud is the show)
Noise Floor (how loud is the noise when you stop talking?)

And it gives an opinion of whether you passed or not and why.

The newer version of the tool is easier to read. Same information.

Download this from, unzip it and drag it over to the Audacity PlugIns folder. Restart Audacity. Have you installed plugins before?

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You are an amazing resource.

No, I haven’t installed Plugins before and am hesitant to do so until I finish this project in case I totally do something stupid… Are there things I should be very aware of before I start?

Thanks for the suggestions about turning away when ‘shouting,’ etc. I may have to record some of the louder segments or figure out how to use the Envelope tool. This book has a lot more dialog than other three I’ve narrated and I guess I need to work a bit on my delivery…

Back to recording, but now I’ll be more careful.

And then I’ll look into the ACX-Check and other things you suggested.


ACX Check is a “Nyquist” plugin, which is a format developed by one of the Audacity developers, so generally very safe for use with Audacity.

The released ACX Check is here

To download and install Nyquist plugins, see


I haven’t installed Plugins before

Then don’t worry about it until you’re at a stopping point. It’s just a much more convenient form of what you’re already doing.

When you select the envelope tool, it will present two blue lines on the timeline. They’re rubber bands. You can click on them and they will bend and move. More importantly, the audio underneath them will also bend and move.

Zoom in to what you perceive to be your loud portion and move the blue lines around until your volume is suppressed. Attached. Pretend that little segment of audio in the middle was too loud.

Play it to make sure you didn’t create a theatrical glitch or odd sound. Select the “I” Beam tool when you’re done and the changes will stick.

Are you conversant in Zooming? There are billions of zoom tools and variations…

…but I only use three:

Drag-select something and zoom into it, Control-E (you can do this multiple times until you zoom in far enough)
Missed it. Zoom out a little bit Control-3
Finished, zoom out to the full show, Control-F

While you’re zoomed in, you can slide the show slightly sooner and later (left to right) with Shift -Scrollwheel.

Yes, there are automated tools to do this loudness thing, and any second I’m going to stop running around with “living tasks” and find them.

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