Noise Floor passes in ACX test- fails in ACX

My book failed 3x in ACX, all 15 files for noise floor. After reading through all the forum topics and watching several youtube videos, I thought I finally got it. I downloaded the ACX plug in for ACX Check. I updated my software. I used Limiter and Amplify to make sure my 3 ACX checks all came back passing for Peaks, RMS and Noise floor. All passing. Every file. I even applied a noise gate at threshhold 27.97. Noise Floor for all files comes in around -65 to -85 depending.

I sit in a closet. I use a professional microphone with a Scarlet Solo. I have a blanket buffer in front of me, clothes behind me and the only “noise” is my voice and the microphone. ACX blanketly tells me all files failed. I contacted ACX tech support. No response yet. It seems to me that a lot of this is throwing spaghetti against a wall and seeing what sticks.

I am perplexed and out of ideas. Audacity says passing and shows me the numbers and ACX just says fail.

Where do I go from here? And I am not as tech savvy as many of you, so please be kind and dumb it down a bit.

Thank you.

I use a professional microphone

Such as? We have to build your system in our heads and the more info, the better.

I contacted ACX tech support. No response yet.

And probably won’t be. ACX is not in the business of solving your tech problems. They’re a marketing and publication business.

ACX blanketly tells me all files failed.

Extreme documentation is important. Please post their exact comments.

You are fighting several converging forces. The world started out with everybody wanting to read for audiobooks. Now with the pandemic, it’s much worse. ACX has notes and postings that they are running in overload and the publication process could take much longer than normal—assuming you pass inspection.

If you read a book, then you have your recording studio set up. Can you read a 10 second forum test?

Read down the blue links. They’re very short. Do not do anything to the voice. Just read it, cut it down to size, and post it.

And speaking of tests, ACX will allow you to read a short test called an audition before you read a whole book (nothing to do with Adobe Audition®). Did you do that?

Who owns the book?


This is their e-mail to me:

Below, we have listed the requirements not met and our recommended solutions. When making revisions, always be sure to revise the originally recorded WAV files within your preferred editing software. We recommend revising all files as this helps to instill good editing practices and ensures all errors have been addressed.

Issue: The files submitted for this title contain excessive background/ambient noise and do not meet our noise floor requirement. Please revise all files.
Requirement: a maximum -60dB noise floor

  • The author owns the book.
  • I have a Rode NT1-A and a Focusrite Scarlett Solo 3rd Gen.
  • Yes, I have a recording studio set-up.
  • "And speaking of tests, ACX will allow you to read a short test called an audition before you read a whole book (nothing to do with Adobe Audition®). Did you do that? - not aware of where this lives

Thank you.

In a bit. I’m juggling a new machine and Real Life.


Completely understand. I appreciate all your assistance.

This normally wouldn’t be a problem, but ACX is running in overload and if you violate any of their rules, it’s out the door.

I boosted the volume of the “silent” two seconds at the beginning of the piece. It’s supposed to sound like gentle rain in the trees on a spring day. Shshshshshshssh. Yours sounds like a boiler factory.

What was that loud tick? Did you strike the microphone?

This is the “Hold Your Breath” blue link detail from that instruction page.

Two seconds. Don’t move.
Not kidding. We can hear your pants and shirt moving, chair squeaking, floor groaning, etc.
We can hear you breathing. You can’t get up and leave because that will affect the acoustic signature of your body. Don’t even think about messing with your phone, etc.
Just freeze.

If the rest of your submission is like that, that may be the reason they didn’t like it. Particularly if you had thumping, cracking, or banging noises in there. They would hate that, even though it passes ACX Check. ACX Check takes an overall noise average. It doesn’t do bangs well.

This isn’t a web page yet, but here is the relevant text for an audition submission to ACX.

ACX-Auditions.txt (1.5 KB)

There is one other way you can pass ACX Check and still fail noise.

Some USB microphones have a distortion I call “Yeti Curse” or frying mosquitoes. That’s a cousin to Fingernails on Blackboard or Baby Screaming on a Jet. It’s “legal” noise, but nobody is going to pass that on to a paying customer.


In order to do your test I had to toggle between web browser tabs. So maybe. My book is on paper and when I start, I don’t move except to change pages which may pick-up. So, the question is, how can I move forward to either A) Fix the files I already recorded or B) test files I record to ensure they will pass? This is all great info, but unless I can execute something tanglble, I am just spinning my wheels throwing that spaghetti against the wall.

How do I get rid of or lessen the “legal” noise. Is it just a matter of turning down the Gain on the Solo prior to recording?


When making revisions, always be sure to revise the originally recorded WAV files within your preferred editing software.


A) Fix the files I already recorded

Do you have WAV Edit Master Sound Files? It’s a mistake to edit and master your chapters and then immediately make the MP3 you submit to ACX. If anything bad happens, you have no convenient recovery. You can’t edit, change, or correct an MP3 without causing sound damage and the damage will push you below the 192 quality demanded for audiobook submission.

Open one of your chapters in Audacity. I don’t think it makes any difference which one. Pick the worst one if you can tell.

Use the magnifier tool (magnifing glass) and zoom into about the first ten seconds of the chapter. Go back to the I-Bar tool, drag-select about the first ten seconds, File > Export > Export Selected as WAV. post it here.

Now do the same thing at the end. The two sound files should be the first and last ten seconds of a chapter.

Post back if you have any trouble with the zooming tools.


I do not. Newbie mistake. I just moved locations and did a quick set up in a much quieter area. It’s so quiet, I did your first test and it won’t even register until I speak. I Think I’m going to re-record tomorrow. I will do a chapter and do this test for you that you just mentioned and post it. After this book I started saving originals without tampering with it and then re-saving it after. Thank you.

Morning. looked back at many of your mastering files and I changed locations and did a new .wav forum test for you. When you have a chance, can you re-listen to this new one? This is the raw recording - no tinkering. the new average noise floor is -60.46. MY RMS is still too quiet saying it.s 26.36 - even though I have it set at -20 in the effect limiter.

Question 1 - If I re-record from here, our my chances looking good to not get rejected by ACX given no other extraneous banging, whatever?

Question 2 - Any other tips from you on preferences to change before recording? Maybe to fix the RMS from the start?
Thank you!

I think it’s perfect aside from the color being wrong. it’s brown, not gray. You need to get the B and the W in there. Then reverse the animals and get all 26 characters in 32 letters. Quick brown dogs jump over the lazy fox. Amaze your friends.

I applied Audiobook Mastering like this.

Select the whole reading or chapter by clicking the Select button at the bottom of the Track Control Panel.

Effect > Filter curve… > Manage > Factory Presets > : Low roll-off for speech > OK.

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

Effect > Limiter: Soft Limit, 0.00, 0.00, -3.50dB, 10.00, No > OK.

Analyze > ACX-Check.

While that passes on its own, you still have that motor noise in there, so I applied Noise Reduction of the Beast (6, 6, 6).

And that gives me this.

Screen Shot 2020-07-15 at 7.33.05 AM.png
And this.

If you can find where that motor noise is coming from (mmmmmmm), you won’t need the Noise Reduction step.

Nobody reads directly into ACX from home. The studio people may be able to hit it occasionally by accident, but they can’t do it for a whole book. So if you’ve been going nuts trying to hit all three standards during the reading, you can relax and breathe. Maybe a little camomile tea.

You can’t change anything once you get going. Everything has to match. Each chapter and beginning and end of the book. There was one poster who moved houses in the middle of a book. That was entertaining.

Additional notes.

Audiobook Mastering settings stick, so you don’t have to go through that whole thing each time. The second time and on, I can whip through the whole thing in about fifteen seconds.

Effect > Noise Reduction is in two steps, but again, you only have to do all the steps the first time. Drag-select a noise sample, Effect > Noise Reduction > Profile. Then apply it: Effect > Noise Reduction > 6, 6, 6, > OK.

After the first time, and assuming you don’t change anything, Select the chapter > Effect > Noise Reduction > OK.

This is where written words are misleading. It’s the three volume set: “How To Ride A Bicycle.”

You watch somebody do it and say, “Oh, is that all.”

If you make mistakes you should correct them before mastering as a rule.

And again, if you can find where that mmmmmm is coming from, you won’t need the noise reduction step.

If I didn’t say it earlier, I would have no trouble listening to a story in that voice. We just have to stamp out the technical problems.

I believe you’re the poster child for reading in a commercial sound studio with a recording engineer. The microphone makers insist everybody can buy their microphone, read on the kitchen table, and retire early. Maybe not so fast.

The all-time winner for audiobook production and instructions was Ian in Hollywood (the geographic location, not the dream factory). 39 forum chapters and over a year. But we did get him going and he’s a commercial reader now.

Good luck.


Thank you Koz!! Super helpful! Honestly if I had started with all this I would never had understood it, so I much more appreciate making the mistakes and working back to fix it. And if I have ti re-record. So be it. Learn as I go.

That motor noise could only be the microphone. I turned everything else off.


I’m not kidding. the second time you master, it looks like this.

Effect > Filter Curve > OK
Effect >Loudness Normalization > OK
Effect > Limiter > OK.

…and then at the end, until we find your mmmmmmmm sound…

Effect > Noise Reduction > OK.

That’s it.
Being professionally obsessive, I glace at each settings panel as it goes by, but I don’t have to change any settings unless I used the tools for other jobs.


Copy that. Thank you!

You wanna mess with the mmmmm sound? Or are you all mmmm’ed out?

It’s not the microphone. They have errors, but that’s not one of them.


I think I’m mmm’d out on this project, but I will focus on it more after I get these chapters redone so I can eliminate it moving further. Another book awaits me. Probably next week. Kind of scratching my head what it could be right now. I unplugged a refrigerator. Turned off the central air and the fan. Turned a cellar fan in my wine cellar. (yeah, I got one of those.) I’m in a basement, below ground next to a concrete wall. Nothing directly above the floor that would do it. I’ll use noise reduction for now. Overall sounds much better than my original recordings.

There are tricks to this. Let us know.


I would love to know I will not mess with it until I after I finish my current mess. LOL. There is another mess awaiting me that’s a much bigger book and having this information would be beneficial. The current book is small. I should finish re-recording by Monday at the latest.