How to get ACX specs for audiobook

I’m working on my first audiobook. The author plans to submit the completed audiobook on ACX. Can anyone please tell me step-by-step how to set up Audacity for the 3 ACX specs below? Or just instruct me to which tabs to go under (e.g. Generate, Analyze, Effect, or something else).
ACX says the files must:

  1. measure between -23dB and -18dB RMS,
  2. peak no higher than -3dB" and,
  3. have a noise floor no higher than -60dB.

We can talk you through it assuming you have a voice sound file. Getting that sound file is the interesting part.

There is a posting for ACX Audiobook Mastering.

You should be in the latest Audacity version (2.2.2) and you will have to install two of the special tools to compliment the built-in tools: ACX Check and RMS Normalize.

But that’s way later.

How were you planning on recording the works? Have you ever recorded your voice before? Is there a professional studio anywhere nearby? What some people do is use a “real” studio to get the first book or two out the door and then transition to doing it at home. That allows you to get your theatrical presentation, timing and expression nailed without having to worry about where to put the living room sofa to get rid of the room echoes.

Jumping into it both feet means you need to be the recording engineer and the theatrical performer—at the same time.

The longest message thread on the forum is from Ian who just wanted to record audiobooks from his apartment in Hollywood. It took about a year. 39 forum chapters.

Home recording, particularly to ACX standards is not for the easily frightened.

Give us a push. Do you have your own microphone yet?

If you’re all set up, record a 20 second voice test and post it on the forum. We will run it through the mastering steps and then tell you how we did it… if we make it.


Fair warning, everybody fails noise. Can you tell if your computer is running by listening? I can save you some effort. You can’t do that. Air Conditioning, cooling fans, traffic noises or the refrigerator in the kitchen regularly kill new user performances.

ACX would just as soon you don’t use post-production Noise Reduction and they say so.



Thank you so much for your prompt reply! Please forgive my tardiness and not hold it against me. I was expecting an email alert when someone replied, but I never got that. Now I know. Anyhow, I will be submitting that 20-second audio test, in a few minutes. I am unable to download the ACX Check. I tried well over a dozen times.

By the way, I have begun recording the audiobook, and it’s a great experience. Then I have an eLearning project coming up.

Hello again. If I can still have the audio check help, I have attached here a short mp3 audio. I’ve quite a bit into the book. If I have to do it all over for ACX specs, well…, I’ve learned a lesson, and it will get done. This time next year I should be a lot better. :wink:

Thanks. Again, so sorry for the delay. I’ve gotten everything else situated I think, with sound proofing, mic, etc. It’s just these ACS specs…

I’m responding to my own question, in case someone is following this thread and is in need of the same information. I decided to pay a professional sound guy for consultation. I explained to him that I have already acoustically treated my recording space. This is what he told me:

To get my files to:
-“measure between -23dB and -18dB RMS”" and
-"have a peak no higher than -3dB
ANSWER: I should just do a “Noise Reduction”. (“Effect” Tab)
I already knew how to do this, but you can do a search on YouTube for “how to remove background noise in Audacity” or something like that. That’s how I learned. There are some good videos. You can also find something on acoustic treatment. I’m recording in my closet.

To get my files to:
peak no higher than -3dB".
ANSWER: Normalize (“Effect” Tab)
I highlight the audio, click “Effect”, scroll down to click on "Normalize’. A window pops up; there is a box that says “Normalize maximum amplitute to”… I put -3dB in that box.
(The same window shows a “Remove DC offset” box. I do not recall the audio guy saying whether to check or uncheck this box. Mine was already checked, and I’m going to leave it alone. The audio guy encouraged me that ACX appears scarier than it is. I should just focus on having the acoustically treated space and doing the Noise Reduction, and I should be fine. He’s done dozens of audiobooks on ACX and multiple local commercials. So, we’ll see.)

I hope this helps someone.

You can leave Remove DC checked. If it’s not needed, it doesn’t do anything.

Have you actually tried that process?

We published a slightly different mastering suite.

It is a very New User mistake to read the whole book and only then figure out if it passes. The up side is you’ll be much more experienced when you read it the second time.

I’m trying to track that back. There is a “known ACX Process” that starts with Noise Reduction and nobody seems to know where the original came from.

I got your clip to pass using the existing Mastering Suite. First three measurements and sentence 2/3 down.
Screen Shot 2018-04-02 at 14.28.11.png

This is that clip after patching.