Meeting ACX Audio Submission Requirements

I am looking to record my first audio file for ACX and i see ACX has a list of requirements, including the 4 below. how do I determine if my recording meets these? as the audacity screen shows my recordings all between 1.0 and -1.0.


  1. Each file must measure between -23dB and -18dB RMS.
    Put simply, all files must fall within a specific volume range. By keeping all files within this range - not too loud and not too soft - listeners won’t have to constantly adjust the volume of their playback device.

  2. Each file must have peak values no higher than -3dB.
    By leaving this headroom you’ll reduce the possibility of distortion, which can reduce the quality of the listening experience. This headroom is also needed to ensure files are successfully encoded.

  3. Each file must have a noise floor no higher than -60dB RMS.
    Noisy files that contain background sounds and other distractions make it difficult for listeners to focus on the material.

  4. Each file must be 192kbps or higher 44.1kHz MP3, Constant Bit Rate (CBR).
    Before going on sale in the Audible store, titles are encoded in a variety of formats that customers have the option of downloading. 192kbps (or higher), Constant Bit Rate MP3 files are required so this encoding process works without error. You may upload 256kbps or 320kbps files if you’d like, but the difference in quality heard by listeners will be negligible. Please see our tutorial for creating MP3s to our spec if this work is unfamiliar to you.

[u]Recommended Audiobook Mastering Process[/u]

That will nail your peak and RMS levels every time. Noise is often a trickier issue and since the mastering process usually tends to boost the overall level it will also boost the noise.

Yes. Noise the hard one for home readers. In English, your background noise has to be a thousand times quieter than your voice. It’s not unusual for your laptop fan to be louder than that.

Those are the hardware restrictions generally tested by a robot, but after you pass that, you also have to pass Human Quality Control. That’s when an actual person listens to your work to make sure you can read out loud in a pleasant manner, and without tongue-ticks, lip smacks, and other mouth problems.

As of the sickness there are two other hurdles. ACX will no longer accept an “audition” or short reading to make sure you’re on the right track, and your work has to be available for me to buy on Amazon before you submit.

You can’t read a cookbook.

This is a posting of the kinds of works they will not accept (scroll down).

If you’re set up, you can post a very short voice test on the forum to get rolling.

Read down the blue links. They’re very short.


audacity screen shows my recordings all between 1.0 and -1.0.

That may be slightly too high. A good goal is blue wave peaks around -6dB or 50%.


That’s an actual voice which was slightly non-symmetrical toward high (normal for some people). The bouncing sound meter should occasionally try to turn yellow.

This slightly lower voice volume standard means you can make a mistake and not create sound damage. You should never have your waves touch 100%, either direction, ever.


i read this master process article but i still dont see how you set the Bit Rate for my recordings - for example, how do I ensure Constant Bit Rate (versus VBR) and ensure Bit Rate is 192kbs or higher.

See my reply here:

follow up question - i went through Audiobook Mastering page - and I set all the Effects as instructed - however, one setting continues to change no matter how many times I set it -

Effect > Loudness Normalization…: Normalize RMS to -20dB > OK

everytime i record and do this check, its getting reset to -20 LUFS - then i have to change the dropdown to perceived Loudness, back to Loudness in order to change from LUFS to db.

any idea why this would keep happening??

any idea why this would keep happening??

Yes. That is an actual bug. Unintentional evil software behavior experienced by multiple people on multiple machines. That will be gone in Audacity 3.