Newbie with ACX and Audacity having some troubles

I am recording some voiceover work and want to make sure I’m within ACX guidlines. I have already downloaded the ACX check plug-in and I’ve read countless forums to make sure I’m within guidlines. BUT, I still can’t get the RMS to fall within the accepted limits. I’ve tried highlighting the mono-recorded audio and Effect>Normalize>Normalize peak amplitude to -18.0 dB but that doesn’t work.

Can anyone help?

Thanks in advance,

Effect>Normalize>Normalize peak amplitude to -18.0 dB but that doesn’t work.

The peak is the highest amplitude in the entire file and the short-term peaks don’t correlate well with loudness. RMS is a kind-of average which correlates better with perceived loudness.

0dBFS is the maximum peak of most digital formats, and your digital-to-analog converter is always limited to 0dB. If you “try” to go higher you’ll get clipping (distorted flat-topped waves). But the ACX specs are “stricter” than that.

As you have discovered (peak) normalizing to -18dB will be way too quiet.

If you boost or cut linearly (with Amplify or Normalize) both the peak and RMS will change by the same amount. i.e. If you “Amplify” by -3dB (actually 3dB of attenuation which is the opposite of amplification) the peak will drop by 3dB and the RMS will drop by 3dB.

Dynamic compression or limiting will bring the peak & RMS closer together. That allows you to go “louder” without clipping.

See [u]Audiobook Mastering Wiki[/u].

Newbie with ACX and Audacity having some troubles

Everybody has trouble, especially with their 1st attempt, and especially if they are not recording in a soundproof studio with the help of a producer/recording engineer. :wink:

I’ve tried boosting it with Amplify and Normalize but still unable to pass the ACX check due to an RMS of -44 dB which is outside of the acceptable range.

Can you help me troubleshoot this?

I am recording some voiceover work

You hope to be recording voiceover work.

ACX check due to an RMS of -44 dB

An RMS (Loudness) of -44dB is broken. You should be able to read so the blue waves on the Audacity timeline are visible.

Screen Shot 2019-06-17 at 16.15.36.png
If you can’t do that, then none of the audiobook processing tools are going to work. You will always fail one of the three ACX standards.

Describe your studio: microphone, computer, room, etc. Parts numbers are good. I did my last sound test into a Zoom H1n sound recorder, for example. We have to build your studio in our heads to figure out what’s wrong.

ACX Check is the testing to make sure what you did conforms to ACX Audiobook standards. The other half of that is the Audiobook Mastering Suite which contains the tools to get you there.

Scroll down to PROCESS for an abbreviated version. It’s only three tools. If you get lost, scroll back to the top and read the whole thing.


Audacity > Effects > Normalize is different from the “RMS Normalize” that you have to download and install.

RMS Normalize is the secret sauce for making this proess work—if it’s going to work at all.