Help me with RMS levels and mastering for ACX

Using versions:
Audacity 2.1.3
Mac OSX El Capitan 10.11.6

Hi, I need some help from the experienced people here on how to improve what I’m doing to get the best sound I can with what I’ve got. I’ve been recording on this setup for many other things, and I generally have my gain set much higher but I recently backed it down because someone said that the reason I’m having to do so much noise cancellation is because I had my gain set way too high. But when I don’t set them high, then my input is so low and I end up raising everything with the Normalisation that my room noise goes bananas, so I feel like I’m stuck between a rock and a hard place and I’m not really fixing the problems, I’m just masking them.

I’m using a RODE NT-1 mic with it’s custom shock mount/pop filter, running it through a Focusrite Scarlett Solo (but I have no idea what to turn the Gain knob to for the optimal input).

Now I’ve been awarded my first audiobook on ACX, and I have run the ACX Check on the attached RAW sample:

Peak level: 0.092231 (-20.7 dB) … Passes ACX
RMS level: 0.010194 (-39.8 dB) << Less than ACX -23 dB min
NoiseFloor: 0.000064 (-83.8 dB) … Passes ACX

I’m assuming that the RMS level means that my overall volume is too low. But even on samples where I’ve done my editing steps and normalised everything, I still have failing RMS levels after making the recordings sound quite loud in my headphones, so I don’t know what I’m doing wrong.

Over the past year or so I’ve played around with my sound a lot, following advice found here or there on what steps to take in editing, what order to take them, etc. I always have to do quite a bit of noise removal and I’d like to finally get some advice specific to my actual sample and setup, so that I can stop tinkering and find something I can be happy with, and that will get my recordings to pass on ACX. I would really appreciate someone taking me under the wing a little and helping me understand what I should do to accomplish this. I’ve been toying with the idea of getting another DAW like ProTools or something, but honestly I don’t have the time to learn a new program right now, I have projects lined up for the next several months and need to stick with Audacity because I am familiar with it already.

Can you listen to my raw sample and tell me what you think I should do to achieve a uniform, ACX compliant sound?
I am your willing student… can you help? :slight_smile:

That’s too low. The fuzzy recommendation is to hit Audacity so the multi-colored display just starts turning colors, first yellow and then orange. The meter will turn angry orange and then red if you get too loud. In numbers, you are shooting for peaks at -6dB. That works out to 50% on the blue waves if you’re counting.

I personally stretch my meters the whole width of the window and then change the left-hand reading to -96dB. I think it defaults to -60.

If you like to be theatrical and expressive, you may need to run the meters a bit lower than -6dB. Do Not run the meters all the way up into the red. Ever.

I believe (I don’t actually own a Solo) that the Audacity volume sliders drop dead when you plug in a USB device like the Solo. This is normal. Adjust the Solo volume control until the Audacity meters reach yellow-ish during a performance. I expect the Solo knob to flash green-ish when you do that.

You were correct. Producing a healthy volume at recording is a very good thing. Struggling with low volume or any of the other problems you can have is a post production career move.

Do you have ACX Check? Does that ring a bell? We have a number of programs that can make this process much easier than if you start from zero.

I need to drop for a minute.


Two sins. I’m doing this on a machine not up to date, and I didn’t catch up the plugin management. However, starting from your raw clip. I got this. See the sentence 2/3 down.
Screen Shot 2017-05-02 at 18.26.59.png
I can do even better with noise by using our super-duper rumble filter. It takes out noises such as thunder and trucks going by. Your microphone makes a tiny bit of that by mistake. It’s not part of the show, so taking it out doesn’t change anything significantly. It doesn’t change anything else, but the noise reading goes down.

Everybody wins.

I need to come back.


Yes, I have ACX check already, and when I run it on that original sample, I got these results:
Peak level: 0.092231 (-20.7 dB) … Passes ACX
RMS level: 0.010194 (-39.8 dB) << Less than ACX -23 dB min
NoiseFloor: 0.000064 (-83.8 dB) … Passes ACX
Did you make changes to my sample when you ran your ACX check? I’m wondering why your numbers are different than mine?

On the first recording I made, I had my gain knob on the Scarlett at about 4 (out of 10). If I turn it up to around 7 or 8 it does run much hotter, see the attached Sample2. However I’m still getting low RMS level with the ACX check on this sample as well:
Peak level: 0.567528 (-4.9 dB) … Passes ACX
RMS level: 0.067770 (-23.4 dB) << Less than ACX -23 dB min
NoiseFloor: 0.000670 (-63.5 dB) … Passes ACX

Does this gain setting at least sound better to begin with? Or does it need to go lower or higher? I want to take baby steps to fine tune each step of the process so best to start with my gain and then go on to processing!

Oh, and a few days ago I ordered the Shure A15HP filter which I’m hoping will be some help with the rumbles you mentioned? It’s already on the way so I hope it was a wise purchase!

I know it’s tempting to pay surgical attention to the position of the knobs, but they’re almost irrelevant unless they run all the way up or down. Your goal is to make the Audacity volume meters work out perfect or nearly perfect.

Yes. I applied two different tools to get what I got, one built-in to Audacity and the other custom. You can get custom RMS Normalize from here.

After I got the performance to pass, I found I could do even better with the rumble filter LF Rolloff for Speech.

I did write a Mastering paper. It’s supposed to be on Revision 2 by now, but I haven’t gotten to it.

The top part of that, Notes and Comments is still valid. Read through that.

The second panel Custom Tools you can use to find and install LF-Rolloff. You don’t need the other two, You already have ACX Check and SetRMS is obsolete.

The third panel Process is almost a lost cause. The old RMS tool was almost raw programming and had to be applied by hand. My joke is that it was written on a paper napkin with felt-tip pen over burgers and it’s been used that way ever since. The replacement is RMS Normalize and it’s an actual finished tool.


You need to make sure whatever you produce for correction has at least 3/4 second of shut up and don’t move Room Tone. Noise analysis will fail if you don’t do that and it can’t find enough silence to chew on. I think something like that is built into the ACX submission standards.

Effect > RMS Normalize: Set the target to -20dB. > OK.

(The blue waves may look funny here. That’s OK)

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

Analyze > ACX Check.

You can suppress the small rumble sounds and do better with noise.

Effect > Equalization: LF-rolloff for speech, Length of Filter around 5000. Not critical. > OK.

Analyze > ACX Check.

I expect that to pass like it did here.

Note we didn’t need Noise Reduction. Noise Reduction can be dangerous. ACX has a failure called “overprocessing.” If they can hear you messing with the sound, they will bounce you.

So that’s the basic setup. You still have to read evenly. There is no compressor or any other way to correct for that segment in the middle where you doubled your reading volume by accident.

If the voice theatrical quality seems right to you, it’s out the door — break for coffee.

Do you have the ACX submission standards?


Oh, and a few days ago I ordered the Shure A15HP filter which I’m hoping will be some help with the rumbles you mentioned? It’s already on the way so I hope it was a wise purchase!

You’ll have to experiment. If most of the noise is coming from the microphone (unlikely), then it will help. More likely the noise is coming from the Solo. In that case it won’t do a thing. It could be a combination of the two. Electrically it’s a gentle version of LF-Rolloff.

To translate the two products: LF Rolloff — Low Frequency Rolloff sucks out low pitch rumble and thumping noises. A15HP is a High Pass filter and allows your higher pitched voice to pass but not the rumble. They’re upside down versions of each other.


Sample 2 passes easily by adding LF-Rolloff. So those three corrections are all you need.

Judging noise can be misleading. Set your sound system for comfortable listening volume while you speak. Then, without changing any settings, scroll down to the Room Tone or background noise. I don’t hear anything when I do that. I expect that to pass unless you make silly mistakes. One poster got all the way to final submission and flubbed the number of silent seconds required.


Time for a wet blanket? It’s not at all unusual for someone to read through the first half (or more) of a book and find they got so much better through practice, they start over.


Did you write the book?


Can’t thank you enough for all the help and suggestions Koz. Feel like I’m making good progress, and hope you have more tips for me today! :slight_smile:

Sorry for the delay, I just got back to my computer (on my way to bed - almost midnight in NZ) and I’ve installed the RMS Normalize and the LF-rolloff for speech. One question: I record in Mono, (I had read somewhere that for spoken word you shouldn’t record in stereo, it just doubles the size of the file, and also that ACX ask that you submit in mono anyway, so am I correct in that?) Anyway, even though I’m recording in mono, on the RMS Normalize screen it asks me to choose between Linked Stereo or Independently. What do I choose, or is this a moot point since I’m in mono already?

Oh and to answer your question, no I don’t write. The sample I submitted was just an audition script that happened to be on my screen at the time. I just submitted some samples to my Profile on ACX, and auditioned for 2 or 3 books, and then the next day I got an offer. So I figured let’s finally give this a try!

Now, having heard my voice and my sample, do you have any other suggestions for me? I know they say you should avoid plugins and things like De-essers and noise gates and those sorts of things, but is there anything of that nature that you would recommend for me, that you know from experience doesn’t typically cause your audio to fail ACX final acceptance? I don’t want to do anything to jeopardise that, but I do want to sound as good as I can. For the past year, I’ve been processing the hell out of my recordings, I mean seriously picking through them word by word and using things like Fade In and Fade Out to manually soften all my plosives and heavy esses, and to soften my breaths, because I didn’t know any other way to fix them. But i’m afraid to do those sorts of things manually now because I don’t want them to accuse me of over processing, and it seriously takes FOREVER to be so anal about it all, but I’ve trained myself into being a harsh perfectionist and now every little imperfection in my voice stands out like a sore thumb to my ears. So hearing someone else’s recommendations or evaluation would really help.

Thanks and goodnight, I"ll be back around in about 9 hours and I’m going to start recording shortly thereafter, to see if I can knock this book out today as I’ve been tinkering for about 3 days and I’m coming close to my deadline.

(Also, I do not receive any notices when I get replies to my thread, even though I’ve gone into the User Control Panel and found that this is a Watched Topic, and my email address is correct, and I have ticked Yes under Edit Posting Defaults to say Notify me upon replies by default. So I don’t know what I could be missing here…)

Is it tomorrow there, or yesterday? I can’t keep track of what happens at the date line.

you shouldn’t record in stereo

Some people have to. Some digital adapters force you to record in Stereo and you have to take steps later to split your performance into Mono for processing and submission. You have one of the adapters that allows you to work directly in Mono and I have the other, Behringer UM2. There may be others.

ACX recommends work in Mono but they won’t come after you with a stick if you work in Stereo. They do say once you pick one you should stay there for a project.

RMS Normalize screen

I leave the setting default. It’s one of the headaches Stereo people have. If you link them, Left and Right corrections are applied to both tracks. This keeps stereo imaging correct (violins on the left). The other setting treats Left and Right as independent tracks. This can be handy if your digital adapter puts you on the Left and nothing on the Right. The blank track will seriously throw off linked loudness settings.

it seriously takes FOREVER

Right. You should solve as many problems at the microphone as you can. We assume you’re a business and the mantra is supply a minimum acceptable product for the least cost and labor. Correcting a presentation word by word gets really tired over a book-length show and generates many possible problems.

I know they say you should avoid plugins and things like De-essers and noise gates

I say that, too. Some corrections generate other problems which then need corrections…etc. I was very pleased to get you to submission quality without Noise Reduction. Tools such as that can generate Essing and that means you need a DeEsser…etc.

Harsh, gritting Essing drives me nuts and I didn’t hear any of that from your samples. You have one of the equipment suites recommended by ACX and in general works very well with few corrections.

As a personal exercise, I wanted to find out what I could get away with for a reading. I nearly made it with my iPod.

So no, a very quiet room and reasonable microphone work just fine. I did use a free download recorder rather than VoiceMemo. VoiceMemo has voice environment processing.

That’s not to say you got away clean. The metaphor for a book reading is not presenting before a joint session of the Prince Albert Academy. It’s telling someone an interesting/juicy story over cups of hot tea. I’m not sure if this was intentional or not, but there are natural places for three contractions in your sample and you carefully avoided all of them.

“It is difficult,” > “It’s difficult.” The presentation decision is a little rough if you’re directly quoting published works and the works are written in stilted university-speak. This is where you pay attention to your audience with glances to the person writing the checks.


I’m not sure if this was intentional or not, but there are natural places for three contractions in your sample and you carefully avoided all of them.

You’re right, I am probably a bit too precise when it comes to reading the script exactly as written. There are times that when I’m reading a script and I will slightly rephrase something slightly because it flows off the tongue so much easier but then I get paranoid and I say it again exactly as written. But I am hoping to relax into an easier rhythm and sound more casual so thanks for pointing that out, I needed to hear it and it will be fresh in my mind now.

I watched the video series on mastering on the ACX site, and I have one other silly question. They suggest recording 30seconds of room noise, and then cutting that into smaller chunks to paste into the start and end of chapters, between sentences where needed, etc. But why would you cut up a long session of room noise recording into all those pieces when you could just cut and paste the same section over and over again? I normally do about 6-10 seconds of room noise at the beginning (well I did this because I used it for the Noise Reduction - but no more!)

My next bit of tinkering is going to be to rearrange my environment a bit, move my mic so that it’s not in the centre of there room anymore, but instead is closer to one of the walls that I have treated with thick Autex sound panels. Right now the way it is situated, I have to speak sideways into it so that I can still see my screen to read copy. Up until now, 90% of my recording work has been short stuff (under 10mins or so at a time) so it didn’t bother me much, but I can’t read an entire audiobook out of the corner of my eye, I’ll go even more blind than I already am… :nerd:

I am probably a bit too precise when it comes to reading the script exactly as written.

Neither ACX nor Audacity have any horse in the race here. This is entirely between you and the client—and by extension, the audience. My favorite shows sound like the presenter is speaking to me, not me and 300 other students/legislators.

I have heard suggestions of pretending there’s a cup of tea in front of you and you’re speaking to someone on the other side of the table. I’m not a presenter, so I’m taking their word for it.

But why would you cut up a bit room noise recording into all those pieces when you could just cut and paste the same section over and over again?

I can answer this using SWAG technology (Scientific, Wild-Ass Guess). The mind has a remarkable ability to turn meaningless garbage into valuable information. Historically, it let us recognize hungry tigers hiding in the jungle. More recently, it’s responsible for subliminal experiments, etc. I wouldn’t be shocked to find after multiple repetitions that listeners begin to recognize that one chunk of background noise. It doesn’t have to be explicit. Just that niggling feeling that something’s not quite right. Anything that distracts from the story is to be avoided.

There are clear standards for submitting silence along with your voice work. It’s not all just start talking and then stop. One thing you can do is intentionally record silent heads and tails so all you have to do is cut the room tone down to the proper amount.

rearrange my environment

Fatigue also contributes to the beginning and end of a chapter not sounding the same. Not recommended.

I would not have picked the middle of the room. There are some actual scientific reasons not to do that.

You don’t always need expensive sound paneling. I did some perfectly fine presentation recording in a storage room surrounded with boxes of statements, billing and archival paper records. Given you have a quiet neighborhood, a stuffed garage can work for the same reason. Echoes don’t have a chance in the presence of all that acoustically dead, oddly shaped and positioned cardboard. The goal is to avoid sounding like you’re recording in a bathroom.

I recorded people in bare, live conference rooms using furniture moving blankets.


By the way, how do you change that exactly, I’d like to make the numbers easier to read on my weak eyes!

I’d like to make the numbers easier to read on my weak eyes!

Oddly, my change doesn’t do that. I extend the range of the sound meters with Preferences > Interface > Meter dB range: 96dB.

Then I grab the meter edges and push and pull until they fill the frame left to right. The other panels should skooch out of the way when you do that. I think you used to be able to make the meters taller… I don’t remember that one. You can undock them and push them around your screen whether or not they’re in the Audacity Window.

But that’s not why I do it. Nobody is going to be looking at -96dB sound levels. That’s down where atoms vibrating make noise, but I wouldn’t mind knowing what’s going on just below -60dB. That’s the area where turning off your noisy CFL desk lamp can make a beneficial difference, such as reducing noise from -65dB to -68dB. If your meters stopped at -60dB, you would never know.

Doing this dance to the meters is visibility neutral because the area around the -6dB colours doesn’t change size.


Ahh ok, well at least there is a broader color meter to catch my eye if things go awry! I often record very vibrant dialogues and scripts that go from near whispering intimacy to loud arguing/yelling and that is where I fear I am going to have the most trouble trying to get everything to meet requirements.

Also, just another question… so I’m doing great with just the RMS Normalise and the Speech Roll-off now that I have my gain turned up so high. However, I’m noticing in a few samples I’ve recorded and ACX checked, that my Peak level is exceeding limits now. What is the best way to rectify this without making other changes I shouldn’t? For example my ACX audition for that childhood obesity book I was working on is ready now, but I noticed that the ACX check shows:

Peak level: 0.911381 (-0.8 dB) << Exceeds ACX -3 dB max
RMS level: 0.101131 (-19.9 dB) … Passes ACX
NoiseFloor: 0.000263 (-71.6 dB) … Passes ACX

If this were my recording to be submitted to ACX for approval, I’d need to know best how to correct that. Should I Normalize? Use Limiter?

If if helps to see the recording you can access it here:

Oh, and the good news? I got my 2nd Offer today. I’m over the moon, and so glad that you’ve helped me to streamline this processing chain down to a science, it feels much less daunting now to think of doing such long recording projects now that I feel more in control of my mastering skills :slight_smile:

You didn’t follow the rules. Effect > RMS Normalize > Effect > Limiter > Effect > Equalization: LF Rolloff.


Oops! I totally missed the Limiter instructions… going back to find those now!

found it!

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

Do you have any words of wisdom about how to go about these sort of chapters, will the settings you’ve already given me help sufficiently under these conditions? I know that I need to avoid clipping (red on the meter) at all costs, but should I start at a lower gain setting from the beginning to leave upper room? Or get further away from the mic during the louder segments? I am just worried that the normal speaking parts have to match the other sections/chapters, and how do I keep from getting too loud with the screaming/theatrical bits?

No rush on this answer if others need help… I just know that I’ll have to do this eventually, but not this week…

That’s it.

We never used to be able to set RMS (Loudness) directly with any reliable tools, so we always had to work around the barn with indirect tools and hope to goodness everything came out right eventually. Not any more. flynwill developed a proof-of-concept RMS tool and steve developed a finished effect. That would be SetRMS and RMS Normalize, resp.

In English: Adjust loudness, Limit those occasionally troublesome blue wave high tips (peaks) and check for Noise. The three ACX specifications in three tools.

Noise can be messy. That’s the step that can split depending on what you have wrong, and that’s the step that prevents us from designing a single mastering tool.

Rumble takes one tool, microphone hiss takes a tool and Yeti Curse Whine takes a third. Each one slightly damages the sound, so we can’t just throw 'em all in there. We have to find the appropriate one.

And to be clear, you make full ACX Conformance without the rumble filter, but it’s close. Since you have a woman’s voice and you have a little rumble, LF-Rolloff is perfect.