Reading ACX Check

There’s something about the read-out from the ACX Check that has been puzzling me. I can’t find anyone talking about here.

What do the four and fifth lines mean? They seem redundant, but give different values than the first RMS and Noise floor figures.

What is RMS (A) and Noise Floor (A)? How are they different from the first three values?

I presume that they mean “A-weighted”. See:

The first three values and the sentence 2/3 down are the only readings you need for ACX. Those are the hardware values and are the tests performed by the ACX Robot—the first test in the series for acceptance.

The other values are “Since We’re Here.” Once you go through the craziness of actually programming a test tool, the other numbers are relatively easy to derive, so there they are. The “A” values are similar to the plain values, but they follow, more or less, the ear sensitivity. If you go far enough up in pitch, only dogs can hear it and if you go far enough down, only cats can sense it (earthquake, thunder). But it’s all sound.

If you have someone show up at your place of work with a sound meter testing for hazardous or dangerous sounds, that meter will be using the A restriction. All the stuff most humans can hear. That’s the one built into most laws and codes.

ACX uses the plain readings, dogs or not. So those are the values you have to meet.

A word on noise. The standard value is quieter than -60dB. You should not celebrate if you make it to -60.5dB. You have to make it quieter than that because you have to do it, reliably, over the whole book. The fuzzy rule is -63dB to -65dB.

Further, if you have computer fans or other irritating noises, you can technically make it, but you may fail the second ACX test, Human Quality Control. That’s the one where a real human listens to the work and tests for theatrical reading and presentation quality. That’s the acting test. They’ll never pass one of those screechy laptop fans.

Home readers never pass noise. It’s a lot harder than it looks. Background noise has to be 1000 times quieter than your voice. If you can tell your computer is on just by listening, it’s going to be a long day.

We publish Audiobook Mastering Suite. Three tools that guarantee Peak and RMS (loudness) and if you read in a quiet room, Noise should work by itself.

If you have troubles, post back and include (if you wish) a test sample.

Go down those blue links. It’s pretty short.


Thanks for the reply. We talked on another thread for a good while, much earlier in the year.

It took me a lot of trial and error, but I built myself a portable recording booth, that, with the Zoom H2N you recommended, gives me noise floors around -70. It’s in my bathroom, actually, that, with a little calking around the door is surprising soundproof. Adding lots of acoustic foam to my tiny recording booth that collapses when it’s time to use the bathroom as a bathroom, has made it nicely sound-deadened. I’ve recorded and edited 13 hours to complete my novel and am about to send it on to Audible. I need to find advice on how to convert it all to the required mp3 format (or whatever) Everything is still on .wav. I know I read it here before.

I’ll post some video of my home-made booth to that old thread. You asked me to do it, but it went through so much evolving over the months, it’s not till now I can do it. It was heartening to see an article that said it costs about $3 to $4K to produce an audiobook. I know I’ve easily lost that much in income with the time I’ve had to steal to get this done.

I did a lot of video editing back in the day and think I’ve become a competent audio book editor. I’ve become rather compulsive at editing out those loud T’s and S’s I tend to make. I think I could give somebody a good deal narrating and editing whatever.

gives me noise floors around -70

After mastering? That’s about right. I can do something similar with my H1n.

I’ve recorded and edited 13 hours to complete my novel and am about to send it on to Audible.

Did they pass a sound test or are you submitting cold? Submitting cold can be an adventure. “Thank you for your submission. We liked your reading, but there is an error you will now have to correct over 13 hours of work.”

You can submit a short sound test for their inspection.

I need to find advice on how to convert it all to the required mp3 format

Open each chapter WAV file and Export.

MP3 conversion is built-in to Audacity 2.3.2. If you’re using an Audacity version before that, you will need to add the Lame software. Audacity has been able to play MP3 forever, but making one was registered software until recently.

. It’s in my bathroom, actually, that, with a little calking around the door is surprising soundproof.

Those surprises are nice. I found the reason my tiny third bedroom looked a little funny was somebody in its history soundproofed it.

Did I show you the forum test process? It’s 20 seconds.


Fair warning when you do submit, more than one reader got bounced when they got the amount of before and after room tone wrong.

Screen Shot 2019-09-26 at 19.08.18.png

Yes, I’ve heard you admonishing us to get the room tone right. I’ve made sure each file has that.

I did send them a sample. They said it was fine except for mouse clicks. I then spent a lot of time and money trying to find a mouse that was silent, only to realize they don’t exist. But then I realized those were not mouse clicks. They were jaw clicks. Ain’t a damn thing I can do about them except delete them every time they occur. They happen just before I take a breath, so that’s just part of my routine. I can see the waveforms at this point. I don’t even need to hear them to spot 'em. I have some clean room tone loaded in my copy and paste and zap 'em.

I’ve gotten finicky enough to where I would either trim or reduce the volume on many of my S’s and T’s, though I think I’m going overboard. I know there are still some there in earlier chapters. If they are as finicky I’ll have to give it all another pass, just looking for S’s and T’s, but for now, I’ve got to get this Methusala project moving forward. Fingers crossed.

If I were starting over at this point, I’d make a point of chewing some gum then pushing the gum in between my teeth at the front to reduce those mouth noises. It actually works.

Here’s the prologue:

I can see them getting upset about the music. That’s instant copyright issues.

Everything else sounds OK.


I won’t use it without her permission. I recorded that myself. I listened to an audiobook that did that with music at the front and I thought it was effective. Aside from copyright issues, do they have any problems?

It wanders away from the metaphor of someone telling you a good story around the kitchen table over cups of hot tea. This is not Radio Theater.

I think you should be crystal clear you’re going to do that before you dump a multi-hour recording on them.


Do you mean I let them know at the outset this is the only music in the piece?

I don’t know. I’m thinking about this. I’ve listened to a number of audiobooks via my Audible membership and there are varying levels of theater going on. Alfre Woodard, I assume, was well paid for her narration of “Tar Baby.” I imagine the budget was justified with the expectation that Ms. Woodard would act out all the characters in the book, which she did. It was obvious she put a lot of work into developing each of these characters. Ron Chernow’s biography of Grant was narrated by a man who did some subtle acting, changing his delivery when reading Grant’s lines as opposed to his wife’s. I know one of these books I’ve read had a brief clip of music at the outset to set the mood. That’s where I got the idea. Americans have no idea, on the subject of Serbs, that we are people who just spent half a millennia an unwilling part of the Middle East. I love that little clip because it demonstrates viscerally that’s where we were, and it shows how we felt about the experience. All in a minute and a half. That’s what art is all about.

I just listened to “The Dead Drink First.” It contains a number of poor quality recordings of phone conversations. At first, I was surprised Audible allowed them, after all my training here. By the end, I thought them priceless. They were recordings of elderly WWII vets talking about their traumas. The book in print would have nowhere near the impact of the audio version.

At the end of the day, we’re artists. I cringe at the thought of some lower-level censor cutting out all those phone recordings, for example, because he had a book of standards to uphold and that’s what he’s going to do. I’m hoping they’ll give me somewhere to explain my intentions when I submit and that there are competent people to contend with. I don’t imagine I get the same crew as Ms. Woodard.

Do you mean I let them know at the outset this is the only music in the piece?

I think you should tell them there’s music in the piece and let them tell you what the requirements are.

I do know telling them the singer said it was OK is not going to work. You should resolve that before you sit through a couple of hours of upload. They won’t discuss it with you. They will bounce the submission at the first problem with brief comments how to fix it.

This is all up to you. I’m telling you that you hit something with storm clouds over it.

And if I haven’t been Mary Sunshine enough yet, we’re assuming that’s the only thing they find wrong. You are a New User.


Do you know what they will need in terms of written permission?


Thanks. I’m just going to take them out for now. Time is of the essence to get this thing on the market.

I submitted it all yesterday. They said the review process should take 10 to 14 days. Have they improved their process lately, or is that just what they’ve been saying when it really takes about 6 weeks?

should take 10 to 14 days.

That’s about right. Posters used to submit and then get a fresh cup of tea to wait. I said, “You know… it can take up to a week…” That was about a year ago.

It’s faster if you mess up the hardware tests: Peak, RMS or Noise. Those are automated and those die fast. It takes longer if an actual human has to listen to it later for theater and voice quality.

It’s gotten longer because everybody with a pulse wants to read audiobooks, make a fortune and retire to a nice cottage in Mal d’Mare on the French Côte d’Azur.

You’re in good company.


I can’t prove this, but I suspect strongly if this is your third or fourth successful book, it either doesn’t go through testing, or it goes through on greased skis.

It’s the New Users where they have to check everything.