Noise Floor

Good evening,

I am recording my first ever audiobook. Unfortunately, I chose a long one (3.5 hours) and after watching a lot of YouTube videos, I thought I had the editing under control. I guess not, because I submitted the audiobook and received notification of items that need fixing. :frowning: All of the items the picked out I can fix with minimal effort, but one of them I am entirely clueless on. It stated the requirement is a maximum of -60db noise floor.

I downloaded a plug in titled ACX check, which runs its check and states I meet ACX requirements, but it didn’t pass the inspection once I turned it in. :question: Can someone please please please help me. I am second guessing doing this whole narration thing, but have literally spend probably 10 hours trying to get this book completed. Any help is so much appreciated!

I have attached a snippet of what I see in audacity when I run the ACX check.

Do you see the third reading down where it says noise is -233dB? That’s impossible. Did one of the YouTube videos tell you to Generate Silence in your reading so you pass ACX? That’s not a real background noise reading. The background noise in your performance is supposed to be measured by making a normal recording and then stop moving and hold your breath for two or three seconds. That will then record the sounds your actual room is making, called “Room Tone.”

Guaranteed it’s not going to come in at -233dB. Much more likely -40dB to -70dB.

And yes, people fail this all the time because most people’s houses are terrifically noisy and we just get used to it.

ACX Check is easy to fake out because it blindly searches for the quietest part of the show and measures that. It has no idea -233dB is not a rational number.

Do you have a good backup of your reading? The rule is be able to point to two separate places that contain your show. That’s so you have a safety copy when the dog eats your laptop. Did you use Audacity Projects to save your work? If all the projects still open, File > Export all the chapters one at a time as WAV (Microsoft) 16-bit sound files. You can get into trouble with Audacity Projects.

Do a test recording and post it on the forum. This is the format. Do Not add effects or filters. Just read it, stop, export as WAV and post it. Content isn’t important. Read the milk carton.


I would not be shocked if ACX Quality Control looks for irrational numbers like that and manually and very carefully measures noise rather than relying on the automation.

It stated the requirement is a maximum of -60db noise floor.

Yes, that’s the specification, but what exactly did they say?


As a beginner you might be interested in a my basic introduction to ACX reality:

Here is a sample of one of my clips. I will do just about anything not to have to record all of this audio again- literally hours and hours of recording :cry:

Sample.aup (2.65 KB)

An AUP is not a sound file. It’s the Audacity Project manager text file. This is one of the problems you can have with Audacity Projects.

Do a 20 second reading as you have been doing according to that simple format. File > Export > Export as WAV. The panel defaults to 16-bit Microsoft like this.

Screen Shot 2018-09-05 at 15.14.14.png
Click Save, and post it here.



I’m surprised you got Noise Gate to work. That’s not a particularly well-behaved tool and worse, if you do anything wrong, ACX can hear artifacts. They hate processing artifacts.


Here you go. Seriously, thank you so much for your help.

Could it be because I clicked “Generate” and then “silence” to get my 1 second of silence at the beginning and end of the clips?

Also, here is a sample of an entirely unedited clip.

Clearly I have no idea what I am doing :laughing:

Your test has quite a lot of AC hum in it – peaks at 120 & 240 Hz. Quite audible even where you are speaking. The recording is otherwise fairly clean. It might be possible salvage your hours of recording work using Audacity’s noise-reduction plug in, or a filter based on those noise peaks but it will have some effect on the sound of your voice.

Do you have the unedited original recordings?

But before you do any additional recording you need to track down the source of that hum and fix it. This is where we ask you to tell us about your kit and how it is all connected. What kind of Microphone, preamp, computer, etc. Is there a fan, refrigerator or other motorized device nearby your recording space? (I’m guessing not, this sound like hum induced directly into the signal from the power lines to me.)

I did not save any of the recordings unedited :sob: huge lessons learned in my first recording. The recordings I submitted to add I used the noise reduction setting after taking a sample
Of the recording with just background noise and then put in 100 in the noise reduction box.

I believe it is because there was a fan going in my room during the entire recording :frowning:

Where do I go from here?

Have I told you how much I appreciate the help?!

I will admit that I came late to this party and so didn’t listen the sample (processed) clip before now.

Was the fan on the entire time you were recording or only part? Or only for that second test “raw” test clip?

I’m a bit surprised that the objection was with the signal to noise ratio, since that is clearly just fine. But it sound like you must have used the noise gate in addition to the noise reduction or something similar. The voice coming out of dead silence effect is known to trip the ACX alarm bells.

I’ll defer to others as to whether or not there’s a way to salvage it.

Thank you for your input.

The fan is on the entire time, even when I did my test sample. I wanted to keep everything the same for you to hear.

My fingers are still crossed it can be salvaged. Any advice is so much appreciated!

Literally, if someone is willing to help me fix the noise floor on these to make them usable to submit to ACX I will pay $30 per hour.

I’d love to learn what I did wrong and how to edit these files properly for the future so I don’t run into this again, but want to give this customer the files they’ve been waiting for :heart:

I forced it to pass technical conformance, but you sound like talking into a milk jug over a bad cellphone (attached).

Screen Shot 2018-09-07 at 19.05.55.png
I don’t think we can make your raw readings pass voice quality and we can’t take effects out of a finished production.

If you’re throwing bux, throw them at a real studio. Walk in, record the work and walk out. You can certainly stick with us here, we have a good track record for getting people published, but it could take weeks. Nobody is going to publish by Monday in my opinion.


There is a sister forum posting to yours having troubles getting his voice stuff up to ACX. We’ve been the first ten days just getting his microphone and environment to work.

— No, you can’t have a noisy computer running in the same room with your microphone.

— No, you can’t leave Windows Voice Processing running while you announce. That’s probably what’s giving you that milk jug sound.

— You can’t fix everything with filters and effects. ACX hates that.


And don’t double post.


Clearly I have no idea what I am doing

That’s not a problem. We can fix that.

We can’t fix: “I need it by noon.”

You’re on your own there.


Any hits on your email? It’s usually a bad idea to leave a working email address on the forum. It attracts bots and spam. Have you gotten any ads for new kitchen cabinets in Manchester?