What setting/tool to achieve acceptable RMS level for ADX?

I’m practicing audiobook narration. I’ve got a clip and I’ve run the limiter to get the peaks below the -3.0 dB limit for ADX, and I ran the ADX check and it’s telling me that my RMS level is too low. I’ve spent an hour trying to figure out what tool to use to bring it up to meet the ADX requirement, but I haven’t been able to get a handle on it. I’m running Windows 10.

The RMS level is -26.3.

Is it possible you mean ACX?

We designed special tools and processes that make it relatively convenient to read for audiobooks.


Read through the whole thing. It’s a mini-tutorial on how to record your voice. Also fair warning, you should not pick one tool out of the suite and try to make it work by itself. It’s a matched collection of tools (en suite) and they depend on each other.

When you post back, tell us about your microphone, connection type, computer type, environment (room) and anything else you can think of. If you fail, noise, we’re going to ask you all these things anyway.


I’m leap-frogging over some of that. If you have a problem you can’t dig yourself out of, post a sample of your reading on the forum. You can use this handy format:


Or you can post a bit of what you already have. It should be in WAV (Microsoft) format and under 20 seconds if it’s mono (one soundwave) or 10 seconds if it’s stereo. It’s strictly limited. You can’t submit a book chapter.

Scroll down from a forum text window > Upload Attachment > Browse.


Thanks for the reply. I did mean ACX, not ADX. I think the RMS-normalize is the missing tool I was looking for.

I carved out a space in my wife’s fabric storage closet that I’ve padded with bed-topper foam (the recording space is about 2 feet wide by 4 feet deep, by 8 feet high, or so. It’s got a little shelf that I set a CAD U37 microphone on, and I speak from a about 18" away. I drilled a small hole and ran the cord through the wall, so my computer is outside my recording space. As long as my house is relatively quiet, there isn’t a lot of ambient noise, and I didn’t fail the noise floor test, even without noise reduction.

My computer is a Windows 10 64 bit (v.1709) PC that I built, with a Gigabyte 99OFXA-UD3 R5 motherboard and AMD FX-6300 6 Core Processor and 8GB of DDR3 RAM. The hard drive is a Samsung SSD, with an additional 1TB drive for storage.

I’ve put a sample of what I’ve been reading below. It’s got some talking and some silence. I ran the ACX checker on it and it passes the noise floor, but fails the RMS range. I’ve been using a public domain Bible (World English Bible) to practice my reading, and uploading the selections to YouTube for family and friends. My goal is to get my whole process as technically perfect as possible so that I can quickly and easily record other things with a high level of quality. Hopefully, my voice isn’t too bad. I’m a little nervous to put this out there.

Thanks again for the help.

Nothing wrong with that.

Step one. Split stereo track to mono with the drop-down menu on the left. Delete one track. ACX would just as well you submit in mono anyway.

Track 1 is straight Mastering Suite 4. Your work passes everything, but you are a hair’s breath away from failing noise. Half dB means if you shift your butt on your chair the wrong way, you could fail.

Track 2 is the addition of “Noise Reduction of the Beast.” Effect > Noise Reduction 6, 6, 6. The work passes all three ACX conformance rules easily and probably even sounds like you.

This is how to use Noise Reduction. It’s two-step unlike other effects.


Screen Shot 2018-01-01 at 15.31.16.png

I think it may be a little crisp but I can’t do anything easy to help. Maybe one of the other elves will add de-esser or one of those filters.

That’s probably good to go. Do you think it sounds OK? This is where having good speakers or headphones comes in super handy.

ACX likes your chapters to match so whatever you do to the worst one, you should do to all of them.

And speaking of headphones, it’s highly recommended that you wear headphones to listen to yourself as you record. That helps makes you self-correcting as you read. Unfortunately, the CAD U37 doesn’t seem to have a place for headphones, and you can’t use the computer headphone connection because of delay and echo problems.

That’s what all these people are doing.

So you’re stuck until you become popular, make a million dollars and buy a larger system.


Oh, one more. Are you using the little desk stand that came with the microphone? There’s no mention of any shock mount, so you can add your own to keep floor and desk noises away from the microphone.

Doesn’t have to be Stephen King. Any heavy book will do it. Do you have a Bible?

Also note the heavy furniture moving quilt on the desk.


Before you go down the noise-reduction rabbit hole I would recommend applying the “LF Rolloff for speech” equalization (Koz: can you post the link?).

I did that on you test clip and immediately got another 6 dB of noise margin.

Otherwise sounds good to me.

(Koz: can you post the link?).

Low Rolloff for Speech is included in Audacity 2.2.1 (and possibly 2.2.0). It’s the identical curve with a more civilian-friendly name.

It’s my standing joke that Steve is world famous for eleven lines of code. If he had signed the work it would be twelve lines.

I did that on you test clip and immediately got another 6 dB of noise margin.

Low Rolloff is included as step one in the mastering suite. It’s possible I missed it…

I did notice another odd noise spike even after all the processing. I need to go digging for it again, but I put it down to fan noise leaking around all the barriers. 97Hz? Something like that. That would be affected by Low Rolloff which starts the slide at about 100Hz.

I’ll go back and see. In fact, being able to reach compliance without Noise Reduction is very desirable.

As we go.

LF_rolloff_for_speech.xml.zip (326 Bytes)

Curioser and curioser. I applied Low Rolloff to the suite processed work and the noise rocketed from -60.5 to -60.7.

I’m using the default length of ~5000. That’s the only obvious variation.

As we go.


Working from a fresh copy of the work, I applied the corrections out of order putting Low Rolloff last and got noise of -60.6.



Hopefully, my voice isn’t too bad. I’m a little nervous to put this out there.

I don’t think you have anything to worry about for theatrical reading. Do you read to a congregation? It sounds like you’ve done this before.

We’re worrying over fine points of technical file quality.


A note. I don’t remember asking; Sample.wav is a raw, unprocessed reading, right? You didn’t do anything to it before you posted it?

If you submit in mono rather than stereo, you can get 20 seconds of performance in before the forum cuts you off. Record in stereo if you have to, split stereo to mono and delete one track.


My ear isn’t all that critical right now, I suppose. I followed the steps laid out in your link (shown below), applied the noise reduction with the 666 settings, and it passed the ACX check and sounds about as good as my voice ever sounds to me.

I don’t really understand what the Equalization is doing, or what “low rolloff for speech” does. I couldn’t hear a difference between my original and the changed track.

I don’t have a shock mount, just the desk mount on a heavy blanket and I try to be really still while I’m recording (I’m standing while reading, and I’ve been using a tablet so I don’t make much noise turning pages). I’ve got a lot of unused reference books lying around, and I might put a few of those under it.

As far as reading goes, I did a little theater back in High School, but my reading has been mostly to my little ones. A guy was looking for a narrator for a book he wrote, and a friend of mine tagged me in the post a few weeks ago. I’d never really considered doing audiobook narration, but I figured I’d give it a shot, given that I already had a microphone and a passing familiarity with Audacity.

I’m going to keep researching, but getting a result that could pass the ACX guidelines was my first major goal, and I’ve achieved that with your assistance. Thanks.

These instructions are in short-form: Location > Tool: Options > OK

Select the whole reading or chapter by clicking just right of the up arrow button (on the left).

Effect > Equalization > Select Curve: Low rolloff for speech, Length of Filter: about 5000 > OK.

Effect > RMS Normalize: Target RMS Level -20dB > OK.

Effect > Limiter: Soft Limit, 0, 0, -3.5dB, 10, No > OK.

You should not be able to hear Low Rolloff working. That’s the earthquake filter.

Many “home” microphones don’t bother to be careful about making noises so low pitch that nobody can hear them. Earthquake, thunder, heavy trucks, Metrobusses, etc. The problem is Audacity can hear them and they screw up the sound processing tools.

So we filter them out as a first step. It’s a rumble filter. The other two are very audible. RMS-Normalize sets overall volume and the limiter squashes the blue wave tips (peaks) which might otherwise create distortion.

In ACX-Speak, that’s RMS between -18dB and -24dB and the Peaks lower than -3dB. As we both found, that leaves noise just at the very edge of not working. Noise Reduction of the Beast easily solves it and can’t be heard working in normal use.

So what’s left is all about you. It may take you a chapter or two to settle in, but I can listen to a story in that voice.


I’ve got a lot of unused reference books lying around, and I might put a few of those under it.

The shock and vibration filter is misleading.

You need both parts. The folded towel provides a low inertia “gooshy” layer that desk vibration has a hard time working through. The mystery novel is the high inertia layer damping out anything that manages to get through the towel leading to almost perfect noise suppression.

But the book can’t make any noises on its own and that’s why paper works so well. Plus the book provides a stable platform for the microphone.

Anybody doing a ballistic, frequency and motion analysis of that little pile would have no trouble covering a blackboard with the forumulae.

Oh and be careful what you do with the wire. You can transmit noises mechanically up the cable. Note the cable loops in this install.

The white zig-zag rubber bands are the towel and the weight of the microphone is the book. If you thump the microphone with your finger, it will sloppy-wiggle for a half-second.