ACX Dang that noise floor

Is your H2 one of these?

If it is, you win the lottery.

Josh recorded the whole first third of his music career on that thing.

It’s an H2 and not an H2n, right? Those are going for new equipment prices on eBay.


TN house wav raw wav won’t work with AC Check. There are moving around and breathing noises at both ends of the performance. There is no clean background noise or room tone.

Use your own words. You don’t have to struggle through contented cows.


One more. The volume is low. The blue waves should reach more or less half way, to 0.5 every so often. Yours are tiny.


Two more.

Issue: Several files contain noise at the start and/or tail end.

Thanks for posting the complete ACX messsage. We don’t have any direct relationship with Audible/ACX, so the only way we know what they’re thinking is copies of the field reports like yours.


We may still be able to pull this out (but maybe not your original readings). Do burn a proper test. We’re on the edges of our seats.

It’s super good to know if you did read it again, it would succeed. Wouldn’t it be a kick in the head if it didn’t?


Trebor, thanks for producing that comparison of “laryngitis”. I have never used De-Ess or De-Click. I see “click removal” in my Audacity 2.3.3, but not De-Ess. That’s a plug-in, right?

I am wary of tinkering with Dynamics. This sounds good, sounds bigger. But I’m not sure I should apply it like wallpaper over 9 hours of audio–

Koz, thanks so much. Yes, I have a real H2, not a H2N. I was surprised to find that I bought it back in 2010! Handy little guy. It’s so excellent in noisy rooms. I was interviewing someone tall (I’m short) in a noisy room, and had to hold it up to him to record his replies to my questions. I couldn’t hear what he was saying, but the H2 grabbed it just fine.

Here’s the contented cows. I don’t know if it’s a good representative sample as far as my voice goes, since I still have some laryngitis. But of course the room noise etc would be the same.

The mic gain was .58. (ignore the 51 in the file name, my mistake). It still failed the ACX check for RMS–it was 24.4. I am seeing green waves that look healthy, but they must not be quite enough.

I tried an earlier sample at .50, and sat real close to the mic, but that also failed (just barely, 23.3, but there was too much breath & mouth sound).

And I tried the gain at .81, and spoke beside the mic rather than at it, but the peaks were too high, and even the RMS was too high.

I would really like to take those original raw wav files (some recorded in MD, some in TN), and start over, editing them for ACX. Do you think it can be done? The MD files should be OK, since they accepted them before. Should I attempt to use the TN files, or are they hopeless?

Cows (Contented).

It’s perfect.

I applied simple Mastering and it exactly fits the ACX requirements.

Screen Shot 2020-01-09 at 9.24.09.png

Nobody can read RMS (loudness) and Peak to match at the same time. It’s Mastering’s job to get them together. If Noise passes after Mastering does its thing, you win. That’s all three.

Noise isn’t one tool or setting. Noise is the college course.

So that’s the answer to the question of could you read it all again if you had to. Yes, certainly.

You have WAV copies of everything, right? You can’t edit an MP3 without increasing distortion. Your archives and safety backups should all be in perfect quality WAV.

I changed your submission from stereo (two blue waves) to Mono (one blue wave). Select the stereo track with the Select button left > Tracks > Mix > Mix Stereo down to Mono. ACX doesn’t require mono, but it makes them happy.

Do you have any way to post work outside the forum? Our services are nice and all, but here, you’re limited to ten seconds stereo. A file posting or archive service? Something?


I like the voice. That’s Lauren Bacall to Humphrey Bogart in “To Have and Have Not.”

“You know how to whistle, don’t you Steve? You just put your lips together and blow.”

How long can you stay exactly that sick?


Koz: Lauren Bacall, LOL. I wish I could cultivate it, like an actor cultivates exactly 2 days’ worth of chin stubble.

Didn’t they get Andy Williams to dub a song for her? I forget which movie.

Yes, I can easily put these files into my Dropbox and send you a link. Would you be able to take a look at them and see whether they are salvageable? That is my first hope.

(How should I send you the link? Email? Text? Just paste it in here?)

If I have to re-record–sigh, it can be done. My vocal weakness is that, often enough, after an hour or so of reading I get a frog in my throat that won’t go away. (Only when recording, not when giving a speech. Go figure.) But if I have to record one hour a day for 9 days, it’s not impossible.

On my mental calendar: our Lent begins March 1, and the book is designed to be read for the 40 days of Lent (40 short chapters), so it would be great if it could be available before that. Which is why I sent it to ACX on December 3. :frowning:

If seeing ACX comments is useful to you, I’ll paste in below the review letter I got from ACX earlier this year, when I sent in the files in February (and missed last year’s Lent). However I no longer have the files that this letter is based on, since I re-saved my recent edits under the same file names.

So here’s ACX’s review of the submission last February:

[You’ll notice that the noise floor evaluation says it applies to “all” of the files, but the RMS evaluation applies to “17 files.” They attached a “graph” showing which files. I opened it. It was not a graph, but a simple Courier-font list–of all the files. ]


The ACX Quality Assurance Team has reviewed your recently-completed audiobook, "The First Fruits of Prayer: A Forty-Day Journal through the Canon of St. Andrew ". We have found 2 issues that must be corrected before we are able to process your audiobook for retail sale.

Below, we have listed the requirements not met, the files affected, and our recommended solutions:

Issue: All files contain excessive background/ambient noise and do not meet our noise floor requirement. Please revise all files.

Requirement: a maximum -60dB noise floor

Solution: In post-production, you may use noise gating or reduction to help reduce the noise floor. Please be mindful that incorrect use of this kind of software can lead to poor sound audio. The best way to go about lowering your noise floor is to identify and eliminate the source of the noise. Often it could be the microphone picking up a loud sound from within the room or it could be a gain staging Issue with your recording equipment. Please be sure that any noise emanating appliances (air conditioner, computer fan, fluorescent lights, etc.) are turned off or isolated so the microphone does not pick up the sound. Our recent ACXU seminar Studio Gear Series goes over the importance of sound proofing your recording area. The Mastering topic in our Video Lessons & Resource section contains samples of what a noise floor should sound like.

Issue: 17 files have a low RMS and are too quiet: Please see attached document for a graph of affected files.

Requirement: files measuring between -23dB and -18dB RMS

Solution: Please raise the overall RMS level of each file to within our requirement. For example, if a file’s RMS is -30dB RMS, it must be raised +8dB to be within our -18dB to -23dB RMS requirement range. Learn Mastering with Alex the Audio Scientist.

After you have corrected the issue(s) above, follow these steps to submit the project for review:

Log into your ACX account, navigate to the In Production tab, and select Title from your list of projects.
Select “Edit” next to the files listed above to delete, replace, and upload corrected .mp3 files.
Confirm the files appear in the order they are intended to be heard.
Click “I’m Done”.

Please be aware that the ACX QA review is not an end to end review of your production and you should always do a full edit, QC, and mastering pass before submission. This is important because errors in the audiobook could garner negative reviews on Audible, Amazon, or iTunes which could result in fewer sales.>>

an actor cultivates exactly 2 days’ worth of chin stubble.

That’s not the hard part. The hard part is maintaining that growth through five days of shooting. Makeup gets a warning if you’re planning on shooting out of order. Today, we’re going to shoot the establishing scenes from the beginning of the show.

I’m not sure where to go with this. We don’t know what Maryland Pro did to your first six books and we can’t take them apart to find out. That’s why we insist that you post uncorrected, clean work for inspection on the forum.

I suspect we can master what you did to passing for submission, but there’s little chance they’re going to match the older work. That’s going to come up. That’s their phrase “… you should always do a full edit, QC, and mastering pass.” Everything needs to match.

I need to drop for a while.


Koz: Oh, so that’s why you went to California!

Thanks, everyone, for all your help.

that’s why you went to California!

I took a wrong turn in Arizona. Wait. What is this warm place with palm trees and surfers?

I’m sending you high quality MP3s of your test clips. I used the classic DeEsser…

…according to these settings.

Screen Shot 2020-01-09 at 17.14.06.png
I used the mastering tools like this.

From here.

The two states are different. Only Tennessee needs the DeEsser.

Here’s how mastering goes.


Maryland/Tennessee Matching


Audiobook Mastering
Effect > Noise Reduction 9, 6, 6


Audiobook Mastering
Effect > DeEsser -20.0, 10.0, 2500.0, 8000.0, 10, 5.0
Effect > Noise Reduction 9, 6, 6


The two groups more or less match with TN being slightly more noisy than MD. Both pass. We hope nobody will notice. You can’t just crank up the Noise Reduction because that may affect your voice.


I don’t remember, have you ever used Noise Reduction? It works in two swipes.

Drag-select some portion of clean background noise. Quarter Second? Half Second? No shuffling, breathing, coughing, etc. Just background sound.

Effect > Noise Reduction > Profile.

That lets Noise Reduction “sniff” the noise like a good dog.

Then you select the whole track and Effect > Noise Reduction: 9, 6, 6 > OK.

That’s the actual reduction part. Gentle Noise Reduction is considered 6, 6, 6, noise reduction of the beast. You need a little more of a push than that so 9, 6, 6 is stiffer reduction. If you go too high, the noise will go down, but your voice will start to sound like you’re talking into a wine glass.

I posted the abbreviated version of Mastering in yellow highlight. If you look at the exhaustive writeup instead, it will tell you how to get the tools you don’t already have.

So yes, if that’s close enough for ACX, you can mix MD and TN readings. Quick word, if you can’t restrain yourself and want to apply additional filters and corrections, you will have to apply them to all the chapters and make sure they don’t conflict with the unique Tennessee settings.


You weren’t expecting a one-button-push solution were you?

This is less terrible than it looks because many of the tools hold their settings. For example, if you set up Effect > Limiter once, the second time, it’s Effect > Limiter > OK. I can whip through Mastering a short test in about 12 seconds. DeEsser holds its settings, too, but not so Noise Reduction. If you close Audacity anywhere in the process, Noise Reduction’s eyes will roll up and it will forget its profile.

There is a one-button Mastering published. but I’m not fond of it because the first step, Effect > Filter Curve is not unconditionally stable. You won’t know if it gets it wrong—it will just start producing bad chapters.

There is an up side. If all the chapters are of that quality, this is one known process to make them pass.


You were never exposed to the full glory of Mastering and voice corrections. Now you know why we strongly recommend a well-behaved microphone and studio. With my Zoom H1n or your H2, it’s possible to record in a dead quiet, echo free room, transfer it to the computer, cut it down, master it and submit it.

No other corrections.

Go make coffee.


Yes, you can get a DeClicker plugin specifically for Audacity here … Updated De-Clicker and new De-esser for speech
( Some store-bought DeClicker plugins work in Audacity, they are simpler to use & faster, but co$t).

I used the louder end of the ACX specifications for both RMS & peak.
For the the best signal-to-noise ratio for the consumer, the RMS volume should be close to the loudest permissible value.
Could maintain RMS near maximum permitted, but reduce the peak from -3dB to -6dB if you prefer less dynamic-range …

Wonderful, thanks so much. Now I know what to do. I lean toward doing the least tinkering possible, but it was helpful to know that you can’t have perfect ACX Noise Floor and RMS right from the raw take. It will always need a little help.

I have my work cut out for me this weekend–2 Introductions, 40 short chapters, and 3 Appendices. But at least I know what to do! Thanks so much for showing me the way out of the thicket. I’ll be back after I’ve done some work on it (and if I run into anything confusing).


It should all be confusing. There are only three people on earth trying to match two different studios.


Yippee! I got the thumbs-up email from ACX today, and the book I was struggling with is now on sale. I will paste in the whole email below, in case there’s anything interesting to you.

I came here for advice a couple of months ago, because ACX was telling me my voice was too soft and the noise floor too high. I already had 7 audiobooks for sale, so I was surprised there was a problem. I recorded all my books from my home office, which isn’t a studio at all, just using a Behringer C-1U. I had a friend who ran the files through his home studio and ACX always accepted them on the first try. But I moved to a different state, and it was time for me to learn how do to it myself. Another complication I had was that the chapters were included in two different home offices, my old one in Baltimore and the new one here in the Smokey Mountains. So there was a lot going against me, but with your help (especially Koz) I got it done, and learned a lot in the process.

Thank you, guys! God bless you! I’ll come back next time – just gotta write another book first.

Here’s today’s email. I see the bounty has gone up from $50 to $75! It is such a nifty bonus–I have actually received a lot of $$ that way. But I just don’t see how they can afford it. They get around $7 every time someone buys one of my books, but if the buyer has never gotten anything from Audible before, they pay me $75? How does that work? Not that I’m complaining!

ACX <>
February 4, 2020


“The First Fruits of Prayer: A Forty-Day Journal through the Canon of St. Andrew” is now on sale at Audible, and will soon be available on iTunes and Amazon, typically within the next 48 hours.

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A major problem with most of my recordings is Esses, clicks, and pops. This forum has made it easy to source the required plugins for Audacity. I am new to Audactiy (less than a week). I find it easy to use. Thanks again for the easy access to the required plugins.

I got the thumbs-up email from ACX today

Congrats. Yes, it’s good to know their exact postings and documents so we can warn others.