Noise floor pass/fail/pass/pass

Hi everyone,
I thought I had finally mastered ACX check tonight when I got the first 3 chapters of my book to pass the plugin. However, that proved to be short lived.

Those chapters were recorded in my open living room which is quite large but has a lot of padded furniture and carpeting. I spent two days doing a DIY studio in a walk-in closet basically creating a nice thick foam cubicle with two layers of carpeting for me to record in because it seemed like I was picking up on the smallest things in my living room.

I applied the three filters that I learned in here to the first three chapters that were done in my living room and they all passed however when I went into my new studio To start recording again tonight I spent hours trying to get test sentences to pass the plugin check. :weary:

I adjusted levels and tried, adjusted levels and tried again applied filters and tried again. I would get them to pass, touch absolutely nothing, record another few lines and follow the same procedure with exact same settings and it would fail noise floor.

Touch nothing record, apply filters, pass. Do it again exactly the same…fail. Rinse, lather, repeat. For almost 3 hours!! Can anyone advise as to what would cause this with noise floor over and over?? Back and forth between passing and failing?? Should I just move back out into my open living room with snoring dogs since they seem to pass easier that way than a padded silent small room!? I don’t get it and I’m about to lose my mind!! Please help!

The Audacity ACX tool needs >500ms of “silence”, (i.e. not speaking), in the audio selected,
otherwise it gives bogus high-values for the noise-floor.

What he said. The tool works on a half-second of “room tone” to figure out noise, but 3/4 second is recommended because nobody can hit the half-second with surgical accuracy. If you miss it at all, the tool gives false high readings.

The instructions for a forum test posting have a two-second pause at the beginning of the performance specifically for this purpose…

…and many people get it wrong. No, you can’t shuffle in your seat, adjust your papers, clear your throat, check Twitter, etc. Those will all give high noise readings that are actually wrong.

-60dB background noise (or quieter) means when you stop moving, the room has to be 1000 times quieter than your voice. It doesn’t take a lot of chair shuffling to mess this up.

Try it. Read a test using those instructions in your new studio and post the test on the forum. Read down the blue links. They’re very short.


Please note that good quiet room tone isn’t just handy, it’s required by ACX for a successful audiobook submission.

Screen Shot 2020-01-15 at 3.19.25.png
There are posters who got rejected because they didn’t stop talking long enough for that requirement. It’s valid to record room tone as a performance and then copy/paste that into your show where needed. You don’t have to hold your breath each time (but you could).

It is not valid to Generate > Silence. That can sound funny and it throws the measuring tool off (and can trigger an ACX alert).


ok here’s the sample attached I recorded with silence in the beginning. Though I’m fairly certain I’ve already been doing this. Any advice on it would be greatly appreciated. I did nothing to it but save it as instructed. This room doesn’t seem like it could get anymore silent. It’s just so odd I had no issues getting the files to pass noise floor in my livingroom.

also have windows 10 and the latest form of audacity

I got your posting to pass ACX with just normal mastering. But.

You have two noise signatures in your work. One is 120Hz. You’re in the US, right? That can be caused by LED, CFL, fluorescent lighting or regular lightbulbs on a dimmer.

The other one is much higher pitch. 552Hz. I’m calling that one the cooling fan in your computer. That one is not significant, but it can be identified and suppressed, it should be.

I’m much more concerned about the 120Hz tone. That one is significant. I can get rid of both of those and you easily pass ACX testing with room to spare. Unfortunately, I did with brute force filtering which affects your voice, too, so that was just for test, not for an actual show.

How are you reading the work? Phone, Tablet?

Print out Contented Cows on paper. Leave all the phones and tablets at least one room away. Leaving the phone in the kitchen is a good idea anyway. They can cause all kinds of radiation and noise problems past actually ringing at the wrong time.

Turn off all the lights and read by candlelight. I know nobody is going to do a book like that, but if all the noises go away, we have our culprit, or a darn good place to look.

Posters have had all of those things cause noise problems.


Wow! Very informative! Yes I was reading the script from my phone which I had silenced. I am in the US and had an overhead light on but it’s a regular incandescent bulb and I know the lighting buzz sound you are referring to but I don’t think it’s that. I’ll try removing my phone from the room and turn out the light and redo the script. I can just work by the monitor light I think since the script is in word. I have a 3 monitor set up.

The fan on my Vaio laptop was running a bit and i was concerned about that from the get go but I’m not quite sure what to do about that or how to eliminate it. I have two monitors plugged into it which help me because I can keep the script on one and audacity on the other.

I maybe can try to move the laptop behind some of the foam barriers I have around me and see if that helps. Sometimes it runs louder than others and I’m not sure why. Even when I don’t have many processes running it can still do that.

I have a 3 monitor set up.

Start Audacity and turn them all off. We’re not trying for Academy Awards here. Just searching for noises. The front of large flat monitors can radiate electrical noise that you can’t hear but can drive a microphone nuts.

The fan on my Vaio laptop was running a bit

Ahem. If you can tell your computer is on just by listening…

I got away with that on one shoot by making a dam or wall between the laptop and the microphone. I don’t remember…towels, jackets…something. It was a large room so I didn’t have to worry about the fan noise bouncing from the walls and coming back. I just had to interrupt the direct path.


ok, light off, phone in kitchen and laptop has decided not to run its fan right now. Is it still there?

If it is I have an idea that just hit me. On the other side of this wall, in another room I have a device plugged in that emits a high pitched frequency said to ward off critters. Creepy crawly ones, rodents etc. I can’t hear it, humans are not supposed to be able to but perhaps that the culprit? It’s supposed to cover 2000 sq ft.

I hope I don’t have to redo the chapters I’ve completed that passed ACX plug in for me because of this! I have so much work to do and a deadline quickly approaching but I don’t want to do anymore until I hear back that this sample is good and free of unwanted noises.

is there a way I can check on my own in the future? Also do you know if AXC and Findaway will fail me for a bit more than the .5-1 second of silence in the beginning that they require? Should I be trimming that 2 seconds down a bit before submitting? I can’t tell you how much I appreciate all the help!

I recorded before reading your other post about the monitors. I really hope it’s not them! It’s so much easier working with them and if I have to hide my laptop and all screens… how do I see the script? I don’t really have the ability to print 68,000 words right now lol.

audacity sample.wav 843.17 KiB sounds like you’re in a box.
audacity sample.wav 862.04 KiB does not have the boxy sound.
The boxiness is visible on the spectrogram as continuous horizontal grooves where sound has disappeared due to destructive interference at certain frequencies.

There’s no evidence of inaudible high-frequency noise, but there is a lot of inaudible low-frequency noise, (below 20Hz), that will raise the noise-floor measurement , even though it isn’t audible …

''862 04 KiB  audacity sample wav'', before-after high-pass rumble-filter.gif

Ok so perhaps I overdid it on the closing myself in. I didn’t just pad the walls in here, I created new ones and they are very close to my body on all sides. Foam-backed with foam presentation board. should I maybe move it back? Or just go back out into a big open living room to record where I started? lol

I couldn’t play the second non boxy sample you sent for some reason it just kept taking me back to the first page of my post when I clicked it.

Will this cause me to fail the human test with Findaway do you think?

I’m attaching pics. Basically I am in a box. Would it help if I just took my box apart and put the foam on the walls a ceiling directly?

Here’s the last pic of it all closed up.

Or were you saying that my first sample didn’t sound like I was in a box but the second one did? They were both recorded in the same exact space.

is there a way I can check on my own in the future?

I did it with Analyze > Plot Spectrum. That’s also what Trebor is doing with that flashing display where the blue blobs on the left vanish. That reflects what Low Rolloff for Speech does. Most of the stuff to the left of 100Hz goes away. That’s where thunder, earthquakes, heavy trucks and metrobuses live. Evil Rumble.

I drag-selected a portion of Room Tone (this is why clean, well-behaved Room Tone is so important).

Analyze > Plot Spectrum and pull the display sideways so detail goes up. I’m analyzing Room Tone and not voice, so most of the stuff to the right goes away. The thin indicator line follows your mouse. Read the little peak window. There are two significant spikes. 544 …

And 120…

Remember, you asked for this.

You are about to experience why it’s a good idea to name your forum posts sequentially. These illustrations are from your first audacity sample.wav 15jan.

I haven’t analyzed your last posting yet.

As we go.


Your “audacity sample.wav (862.04 KiB)” does sound very different from your “audacity sample.wav (843.17 KiB)”,
as if they are different environments.

“(843.17 KiB)” does sound like there’s a highly-reflective surface close by causing the boxy sound.
From the picture, the screens and the desktop are the only near hard surfaces …

Possibly angle the screens so you can still see them, but they are not reflecting your voice back to the microphone.
or change the position of the microphone so it’s at forehead height …

The Yeti microphones have a switchable sensitivity pattern, cardioid is the one to use to minimize reflected sound.

No. Wait. That’s from 13jan…

Anyway, that’s the analysis with the two noise tones in there. The 544 thing is probably your laptop fan noises and it’s not very loud. The 120 may very well be your monitors. Jury’s out.

There are other analysis things you can do. I can’t make out the microphone, but you can aim it. Instead of aiming it to you, aim it at the monitors and laptop and we’ll see if the noise tones go up. That’s how I found a noisy bass cabinet in my music room. Noisy even though it was turned off…!

There is a sister forum posting from someone with very good quality recording equipment and very bad background noises we’re guessing is from air handlers, ventilators and air conditioning systems. Haven’t found that yet, either.

Isn’t making a sound studio fun?


Audacity sample.wav 843 does not have the 544 tone there any more. That’s the laptop fans, right? 120 tones are still there.

I applied Mastering and Noise Reduction and got the work to pass with reasonable elbow room.

Screen Shot 2020-01-16 at 1.34.01.png
I’d probably go with that and stop trying to find that last noise tone.

Drag-select a portion of Room Tone at the beginning of your piece. Effect > Noise Reduction > Profile.

Then select the whole reading with the Select button on the left. Effect > Noise Reduction: 6, 6, 6 > OK.

I’m only dealing with basic technical mastering. That’s different from voice quality issues. That’s two different tests at ACX as well.


Oh wow! That is a lot to take in! Lol I’ll have to study it and digest it all.

So I don’t really have a way to do the new microphone position (at the forehead) unless maybe I can go buy some blocks of foam and stack them higher than my head and do it that way.

The desktop, since that first picture has been covered in a towel. It was already covered in both recordings So I’m guessing it’s those monitors deflecting my voice. So I’m thinking I’ll try moving them. I’ll take one away, keep one and like you said angle it to the side and hope that solves it.

I’m totally puzzled as to why those recordings sound like two different environments. (Eye brow raised) it was quite literally exactly the same each time.

Otherwise all files I should just do the noise reduction you showed me at beginning and end and submit the files and I could possibly pass right?