Format your audiobook files to ACX standards in Adobe Audition, step by step with screenshots. Loudness, peak level, room tone and MP3 settings.
Updated September 2026. ACX's file requirements haven't changed since I wrote this in 2021, so the settings below still work.
In this article, I show you step by step how to format your audio files to ACX standards in Adobe Audition, so you can publish your audiobook on ACX and Audible.
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ACX is owned by Audible, and it brings authors and producers together with narrators and voice over artists. The idea is that anybody can publish without going through a big publishing house. KDP (Kindle Direct Publishing) lets authors publish their books on Kindle, and ACX lets them publish their audiobooks on Audible.
With all that freedom to self-publish, ACX needed a standard to keep the sound quality high. So they set requirements that every audio file has to meet before it's accepted.
This guide walks you through those steps, with pictures, so you know what to do when you're uploading your files.
New to ACX? Start with the basics in my step-by-step guide to start voice acting with no experience, which has a section on the audiobook route, and my tips for narrating non-fiction audiobooks.
Step 1: Start here when you are finished recording
After you've finished recording your audio files and edited them, it's time to format for ACX.
The picture below shows the screen I start from. If your screen doesn't look exactly like this, that's okay. Just follow along from the next pictures.
Step 2: Find the loudness tab
In the upper right-hand corner of Adobe Audition, you'll see double arrows pointing to the right. Go there and click on them.
You can see the double arrows here, and what happens when you click on them.
Step 3: Find Loudness in the tab and click it
It doesn't matter where Loudness shows up under the tab. Click on it and it will take you to the next part of the process.
Clicking on Loudness takes you to another screen in Adobe Audition where you can set Audition to format the files correctly.
Step 4: Your loudness screen should look like this
After you've clicked on "Loudness", your screen should look like this. If it doesn't, go back and repeat the process and it will get you here.
Now that we're here for the first time, we have to set the parameters.
Step 5: Set the parameters for formatting to ACX standards
First, find and click on "Match Loudness Settings" as shown in the picture below. This brings up another panel where you set Audition up for the formatting.
On a side note, once you do this it saves automatically, and you shouldn't have to do it again.
Once you click on "Match Loudness Settings", you should see a dropdown below it titled "Match To". Click on "Match To".
Step 6: Click on ITU-R loudness
Once you choose ITU-R Loudness under "Match To", you'll see "Target Loudness", measured in LUFS (Loudness Units relative to Full Scale).
We want to set this between -18 and -22. I've chosen -20 as the middle of the road. I find that if you set it towards the middle, you won't be affected by a little nudge in volume in either direction.
The next setting to pay attention to is "Max True Peak Level", which is the loudest point in your signal. We want to set this at -3.2 dB.
ACX requires peaks no higher than -3 dB, but I've found that when you go to save a file, it can sometimes come out a little higher, like -2.9 dB or -2.8 dB. With -3.2 dB, you don't have to worry about it.
Leave the rest of these settings alone. You don't need to do anything else with them.
Step 7: Move the file and hit Run
After you've set everything, move the file over to the "Match Loudness" box and hit Run.
You can move the file over by dragging and dropping it. Look at the picture below to see how it should look.
Once you've moved the file over and hit Run, you're ready to check the results.
Step 8: Check amplitude statistics for correct settings
In this step, head down to the lower left corner of your screen and hit the Scan Selection button.
This brings up a series of numbers. The only ones we care about are "Peak Amplitude" and "Total RMS Amplitude".
The "Peak Amplitude" should be no higher than -3 dB. ACX wants the "Total RMS Amplitude" between -23 dB and -18 dB, and with the settings above you should land around -18 to -20. ACX also checks your noise floor (the sound of your room when you're not talking), which has to be -60 dB or lower. That part comes from your room and your editing, not from these settings.
Step 9: Click the Default button to move back to the general screen
Click on the Default tab so you can move back to the general screen.
That way we can move on to making sure there's enough space at the front and end of the file before saving.
Once you're back on the general screen, there are only 2 more steps.
Step 10: Add space to the front and back of the file
ACX requires 0.5 to 1 second of room tone before the audio begins, and 1 to 5 seconds of room tone at the end of the file.
Your audio won't be accepted if you skip this step. Below, you can see where I've set the front and back of the file within ACX's limits.
And here's the back of the file.
Once you've made these adjustments to your file, you're ready for the last step.
Step 11: Save your audio with the correct settings
In this picture, I show you exactly the settings you need for ACX. I'll also list them here.
- 44100 Hz mono
- 16 bit
- MP3
- Constant bit rate, 192 kbps
- Name each file for the chapter, or for the opening and closing credits. You also need a retail sample, which is 1 to 5 minutes of the first chapter.
These are the settings you need to save your file for ACX and get past quality control every time.
After you've clicked "Save As" and put in these settings, hit OK. You're now ready to submit this file to ACX.
Remember that each chapter, the opening credits, the closing credits and so on must be separate files. So you have to do this process for every file you upload.
Doesn't this take a lot of time?
The answer is ... yes, it takes A LOT OF TIME.
A lot of people hire editors and engineers to help once they get busier. I've always been a firm believer that you should learn how to do it yourself first, before you have someone else do it, so at least you know when they've done it wrong.
Also, when you're starting out, the money you make per hour of your time on an audiobook is going to be small, so paying someone extra probably isn't the best idea. But I leave that decision to you.
What about plugins?
Plugins can save you a lot of editing time. Noise reduction can take out background hum. Compression evens out your levels, so your loud moments and your quiet ones aren't miles apart. Then there's the de-esser, which tames harsh S sounds, and EQ, which can clean up a muddy or boomy voice.
Just go easy. If you push noise reduction too hard your voice starts sounding watery and processed, and a listener will hear that for eight hours. The best fix is still a quiet room. Get the recording as clean as you can, and use plugins to polish it, not to rescue it.
An easier way to check your files
If you narrate through Academy Voices, our audiobook publishing side, you don't have to do all of this by hand. We built our own file checker for our narrators, and when it finds a problem it fixes the file for you. Our narrators have published over 750 audiobooks through Academy Voices, and every VO Journey Academy member gets free access.
If you want audiobook material to practice on, try the audiobook section of our free scripts library. And if you're still setting up where you record, I've got posts on setting up a voice over recording studio and starter microphones.
Come see how we do it
We talk about ACX and audiobooks a lot in our live classes. Angela Ohlfest, who has narrated over 250 audiobooks, runs Launch Pad on Thursday nights at 8pm ET, and I teach Marketing 101 on Tuesdays.
You can sit in on all of our classes for free during Free Class Week, Monday 12 to Thursday 15 October. It's live on Zoom. No card, no call.
If you already know you want in, your first month of CORE is $39. You can join here.
Thank you for reading :)
Sincerely,
Anthony
