Regression ACX Errors


A few days ago, I got a rejection from ACX based on the noise floor of several of my files.
So I corrected the errors, cleared it through ACX and ensured everything passed.
But I got another rejection notice today, about the same errors.

So I go back to my mp3 tracks.
And files that had passed ACX check are now failing.

I am ex-military.
I know what its like when lives are at stake based on you following verbatim instructions.
I don’t mind telling you, this is messing with my head.

Please advise…

Failing what? Noise?

Requirement: a maximum -60dB noise floor

There’s two ways you can fail noise.

Louder than -60dB (smaller number) or quieter than -90dB. Loud background noise means your environment or system didn’t stop making noises when you stopped talking. That’s usually the (sssss) or (shshsh) back there. Also air conditioner or traffic noises.

You would think reducing noise to absolutely, total, dead quiet would be good, but they don’t like that so much either because normal microphones won’t do that. To get that, you would have had to mess with effects and filters and they really don’t like that.

Which one do you have?

And now the really good news. You can’t “fix” an MP3 file. MP3 gets its tiny, convenient sound files by messing with the tones in the show—and leaving some of them out. The process is permanent and recursive. If you patch an MP3, it leaves out some more.

You know that business of making a 192 Constant Quality MP3 for submission to ACX? If you patch or change your original submitted MP3, it’s not 192 any more.

This is where you go back to your Edit Master WAV chapters and patch it there, then make a whole new MP3. Also note ACX puts great stress on having your chapters match, so there is no piling effects onto one chapter and not others.

If this was easy…


Rather than batting this back and forth, record and post a test sound file on the forum.

Don’t help it. No effects or patching. Record it, stop, cut it down if you need to for length, export, and post it.


This is a “dB Explained” graphic that might help a little. I drew one for the old forum and didn’t keep a local copy. My bad.

Yes, it is a text file, but I can’t publish that way because computer display systems will insist on distorting the spacing. This thing is all about the spacing.


Here’s your “cartoon” in a Markdown code block (I had to guess some of the spacing):

 <--- QUIET                                                   LOUD --->

 -96dB           -60dB               -23dB _____ -18dB     -3dB     0dB
 Digital Limit   Noise Limit           Loudness Range      Peaks   Clip

Or as a Markdown table (the ASCII arrows conveniently turn in to real arrows too):

-96dB -60dB -23dB … -18dB -3dB 0dB
Digital Limit Noise Limit Loudness Range Peaks Clip

Edit: You can see the source by quoting this post.

Thank you.

The main goal is to illustrate negative numbers. That’s also why I’m getting out of the habit of saying “Larger” or “Smaller” numbers.

Quick, subtract 3 dB from -18dB. I’ll wait.

It’s always “Louder” or “Quieter.”

Also “To Scale” doesn’t work because that puts -96dB over where you parked your car and you lose the graphic relationship between the numbers.

So, cartoon it is.

I picked a .png image file as being the most likely to work for everybody. And I can do it on my desktop without breathing hard.

I’ll probably post it on along with “How to record an audiobook,” (so I don’t lose them again) and I’m not sure what I’m going to do there. “How to” is going to be the basic quick tutorial, only bristling with links.

I haven’t written the links yet.


As far as I know, I can’t title the response to a forum post? That makes handy notes and postings almost impossible to find by name.

That and the expiration dates.

Kozco it is.


Of course. Or it would crowd Peaks and Clip levels.

At least you didn’t include the digital limit of 32-bit float (that’s what, like -900dB? or a single air molecule sneezing?). That’s in the next town over. :laughing:

I leave the unicorns out of the explanations.

Over in “How To,” I state that once you make the MP3 chapter for submission to ACX Audiobooks, you can’t change it. You can, but the explanation is awkward, confusing, and involves non-Audacity software.


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