Problems editing audio book to pass acx

Hello everyone…I’m so glad I found this forum. I hoping I can get some help.
I just finished recording my audio book and I am ready to master. I am having a problem passing the noise floor section. I have followed the guidelines i found online for audacity for Acx but I’m still doing something wrong. I don’t know where to go in Audacity to adjust the settings it is saying I am over. I used Equalization, RMS Normalization and limiter as instructed. i have never done this before and I would really like to understand what I am doing and correct it.

Can someone help me with this or lead me where I can understand how to really adjust Equalization and where to adjust the noise floor, etc. thank you in advance

It depends on what the noise is.

The tools in Mastering 4 will get you through 2/3 of ACX acceptance. Low Rolloff (Equalization) is good for suppressing rumble and low pitch interference. Some home microphones make their own rumble—you don’t necessarily need a truck going by. All gone.

RMS Normalize does what it says on the tin. It adjusts the volume of your show so it will pass the RMS (Loudness) portion of the ACX test. RMS Normalize can bump up your volume so loud it will not pass ACX Peak. So Limiter gently pushes the blue wave tips down so they pass inspection.

That leaves noise.

If you start with a well-behaved microphone in a dead quiet, echo free room, noise won’t be a problem and you can submit for publishing, dust off your hands and go home.

That never happens.

Most homes are insanely noisy but you just don’t notice it. Right this exact second, My washing and dryer are cranking, the refrigerator is running and there’s traffic on my street. There’s zero chance I will be recording an audiobook in this environment.

Worse yet, the noise management tools are only partially effective.

If you’ve read the ACX submission standards, you know that Room Tone (what happens when you stop talking) is a really big deal. It’s included in your submission standards. Open one of your chapters, drag-select about 20 seconds of talking i_ncluding_ two or three seconds of natural silence (Room Tone).

File > Export it as WAV (Microsoft) 16-bit and post it on the forum. Scroll down from a forum text window > Attachments.


There is one harmless thing you can do by accident. You may not have enough silence in the show to measure. The noise measurement part of ACX-Check needs about 3/4 second of clean room tone somewhere in the performance or it will give bogus readings. Room Tone is the natural noise the room is making with you not breathing or moving around.

Shoot a 20 second sound test using this formula.

…and post it on the forum. The instructions are in the post. Do Not apply corrections, filters or effects.


ok i hope this works for the upload

Thank you for the sound clip. It’s not long enough. Do that again except don’t stop talking until about 18 seconds has gone by—and try not to breathe for the first second or two.

We’re not only inspecting for noise. If you’re close enough, I post an audiobook mastered example and then tell you how I did it.


Windows 10
Audacity 2.3.0

I am a newbie also. :blush: This is my first recording and I wanted some feedback to ensure I was within ACX’s requirements before I proceeded. Please let me know, where to view any step by step threads, videos, etc. to meet the following requirements.

-Each file must measure between -23dB and -18dB RMS.
-Each file must have peak values no higher than -3dB.
-Each file must have a noise floor no higher than -60dB RMS.
-Each file must be 192kbps or higher 44.1kHz MP3, Constant Bit Rate (CBR).

Thank you.

Good start.

This is a more or less English version of the readings.

I got your two volume numbers, RMS and Peak to work, but the room noise is MUCH too loud. It sounds like you’re mixing cement in there with you. I can suppress the noise but the fix starts messing with your voice.

Is the computer in there with you? Can you tell if it’s on just by listening? What else could be making fan or motor noises? Air Conditioner? Fan in the window?

I prepared a sample where I made the noise at the beginning worse on purpose so you could hear it.

What could be making that noise?

In audio the maximum loudness is zero (0dB) and everything gets quieter in negative numbers. The numbers aren’t linear, either. When ACX says your background noise (sometimes called Room Tone) needs to be -60dB, they really mean the noise needs to be a thousand times quieter than your voice.

No, that’s not easy. This is where most home recording people fall over. “You mean I have to turn my noisy refrigerator off?”

Ummm. Yes. Or record somewhere else. Can you tell if something is running just by sitting and listening?

Which microphone are you using and how is it connected?


Have you done any public speaking or announcing? Reading to the kids at the library counts. Unless you have some announcing experience, this could be a little painful at the beginning. It’s not unusual for new readers to read the first few chapters of a book twice. They get to the end of a book and realize how terrible Chapter 1 was. That only happens on the first book.

ACX puts a lot of stress on having all your works match and they like natural reading. My silly joke about that is you should sound like you’re telling somebody a story over cups of hot tea (Icy glasses if you’re from the south).


One note. Do Not put punctuation marks in filenames. You’re allowed Upper Case, Lower Case, Numbers, Underscore and -Dash-. That’s it. Other punctuation may cause your show to fail if you have to post it to someone else.


I am asking if there are specific settings I need to set before I start recording (for the items listed ACX requirements below)? I understand what you mean regarding the background noise. I will work on it.
-Each file must measure between -23dB and -18dB RMS.
-Each file must have peak values no higher than -3dB.
-Each file must have a noise floor no higher than -60dB RMS.
-Each file must be 192kbps or higher 44.1kHz MP3, Constant Bit Rate (CBR).

Microphone - Blue Microphone Yeti USB Microphone (Slate) with Headphones and Knox Pop Filter. It is connected directly to the laptop through USB and the headphones are connected directly to the Yeti microphone.

I will have to review the link tomorrow.

Public speaking - yes, I am a former teacher, and I have been master of ceremony, and I have given speeches.

Ok on the filenames.

I have been master of ceremony

So you won’t have any trouble with the theater part of the job. We just have to get you over the technical requirements.

In general, it’s not possible to read directly into ACX—or you might do it once by accident, but you can’t do a whole book that way.

Read so the Audacity blue waves on the timeline occasionally reach about half-way or a bit less. The bouncing sound meter should go up to about -6dB to -10dB, occasionally.

Roughly like this.

Many USB microphones won’t easily get that loud and you have to be satisfied with a quieter reading. With reasonable electronics and a quiet room, this can be done. What doesn’t work is a timeline almost dead flat and a bouncing sound meter in the -20dB or -30dB range.

If you’re wondering why you need to worry about these technical considerations, you are the recording engineer. I know the microphone ads keep assuring you of instant success, but it’s a bit more involved than buying the mic and plugging it in.

Record a voice test and post it on the forum. It doesn’t have to be a Great Work. Read the breakfast cereal box, but do it to this format.

Do Not move around or breathe during that first two seconds. That’s Room Tone or the noise the room is making by itself.


-Each file must be 192kbps or higher 44.1kHz MP3, Constant Bit Rate (CBR).

That’s later. ACX requires submission in MP3 sound format. They have specific business reasons for doing that, but you should do everything in perfect quality WAV and only make the lesser quality MP3 when you submit a finished show.

Here, I turned these into a little better English.

-Each performance must measure volume between -23dB and -18dB RMS.
-Each performance must have peak sounds no louder than -3dB.
-Each performance must have background noise no louder than -60dB.

The noise floor or background noise is not measured in RMS. Background noise may not seem very important, but again converting to English, your background noise should be at least a thousand times quieter than your voice.

It’s not unusual for people to build little table studios out of towels, quilting or sound panels to get the noise down.


I am asking if there are specific settings I need to set before I start recording (for the items listed ACX requirements below)? I understand what you mean regarding the background noise. I will work on it.
-Each file must measure between -23dB and -18dB RMS.
-Each file must have peak values no higher than -3dB.
-Each file must have a noise floor no higher than -60dB RMS.

You’ll have to tweak the levels after recording. As Koz says, you’ll typically be recording at lower volumes. The most important thing is, don’t hit 0dB. If you hit 0dB you are most-likely “trying” to go over 0db (the “digital maximum”) and you are clipping (distorting).

When you adjust the volume linearly (with the Amplify or Normalize effects, etc.) all of the levels will change by the same dB amount. i.e. if you boost by +3dB, the peak, RMS, and noise, will all go up by +3dB.

Dynamic* compression and/or Limiting will bring the peak & RMS levels closer together.


  • Not to be confused with file compression such as MP3. Actually, a side effect of MP3 compression is sometimes a slight increase in the peaks.

Yeah. Stay away from the file definitions until later.

If your bouncing sound meter goes all the way up and the blue waves go all the way top to bottom, That’s the volume where the digital system stops following the live performance. That’s automatic distortion and sound damage. Stay Away!!


Thanks all. I finally downloaded the ACX Check (which I realize does not guarantee anything :wink: ) and now I can see where my main issue is. It is the RMS level. So, do I “normalize” the entire clip? Or what is the “Fix” for RMS levels?

RMS Level
Measure between -23dB and -18dB RMS.

I’m just reading through that again. I don’t think anybody ever asked it that way.

The only two controls you have during recording are quiet environment and voice volume. As a fuzzy rule, record as loud as possible without overloading the sound channel. Voice volume is a lot more unstable that you think, so as a practical matter, record so occasional vocal peaks go up about half-way. That’s -6dB sound meter and 50% blue waves. Those two are the same number with different names.

Those are performance variables. This is all assuming you have a good, well-behaved microphone. You can have microphone troubles. Blue Yeti microphones sometimes don’t get along with the computer. That conflict sometimes gives a mosquito whine sound I call “The Yeti Curse.”

And there’s a third failure related to environment. The modern apartment/house with polished wooden floors and plain white walls is a Hostile Recording Environment. Nobody is interested in hearing you announce in a bathroom.

I got lucky. My house has a small soundproofed bedroom facing away from the street (a former family had a kid that played drums). In fact, I could unwrap a Yeti, plug it into my Mac and record an Audiobook. Very few people can do it that easily.


We posted a suite of tools for Audiobook Mastering.

It is a suite of tools, a harmonious grouping. Start with a raw reading and apply the tools in order. Don’t help. There is one additional tool you don’t already have. You will be downloading and installing RMS Normalize.

All the steps are in the posting.


I was reading that thread right then. I downloaded the RMS normalize already and tried it. Now, I have the exceeds noise issue. I am about to read on. Thanks Koz & DVDdoug.

I downloaded the RMS normalize already and tried it

Those were the wrong words. Using RMS Normalize by itself is dangerous because it can cause other problems. Did you try Mastering 4?

Post a 20 second sound test from a raw, unprocessed reading.

We may be able to tell what the problem is and suggest solutions.


Help…I passed the ACX check initially, then I did the same things exactly and now the noise floor is too high. :blush: