ACX Dang that noise floor

[fredericamg]

With the help of Audacity, I've been recording books for some time, and have 6 or 7 on Audible at present. THANK YOU for everything you do. This searchable Forum has been such a help over the years!

I ran into something with this latest book. I have already recorded the whole book, and a friend mastered it, and I submitted it, and was told that I needed to raise the RMS and diminish the noise floor in some chapters. I have been going through and getting things tidied up for re-submission. I did not know of the existence of ACX Check and what a help that is.

As I go through I'm finding that some of the chapters have a sound that doesn't appear on others, something in the noise floor. Perhaps I will end up just re-recording those chapters, but I wanted to see if it is possible to save them. If nothing else I'd like to understand what I have here, and how to handle it.

I'm attaching a short clip from the raw WAV file

Ch 6 Raw.wav

(1.39 MiB) Downloaded 31 times

, and secondly a clip after I used Notch Filter, then Amplify, then Limiter

Ch 6 ACX checked.wav

(1.39 MiB) Downloaded 18 times

. Hard to believe, but this edited version of Chapter 6 passes the ACX check--this little clip doesn't, but the whole chapter does. I can still hear the sound, though, and think they might turn it down anyway due to that noise.

Grateful for any instruction and help you can give me, even if I do end up having to re-record.

[DVDdoug]

See Audiobook Mastering.

You'll need to get the levels set before any noise reduction because boosting the audio will also boost the noise.

Since you've passed before (with the same setup and the same room studio?) some slight noise reduction will probably get you there.

[kozikowski]

Ch 6 Raw has a stupendous amount of noise back there. Are you in a room with loud air conditioning or other forced air system? That's what it sounds like.

I can't Noise Reduce it. By the time I get it to pass, Noise Reduction is starting to make your voice like talking in a wine glass. If I really lean on the correction, the voice volume starts to wander and throws the other readings off.

ACX Check looks for one good second of background silence in the whole chapter and measures that. The rest of the chapter could be complete trash as long as you have that one well-behaved second in there, it will seem to pass. That's why they have Human Quality Control in addition to the automated testing. There is another common item, too. It has to be room tone or "real" background sound, not Audacity > Generate > Silence. They look for noise values that are too good.

Any idea what that wind noise could be? I guess it's possible it's microphone noise. But if it's coming and going, that's the signature of HVAC or Air Conditioning.

This is not good news. ACX usually wants the chapters to match. Patching up one chapter to not only pass, but match can be a challenge.

Koz

[fredericamg]

Thanks so much for your help. Sounds like I'll have to do some re-recording.

It's funny about some files being like this and some being fine. I recorded all my other books right at that same desk. There must have been something contributing this extra noise, off and on, that I didn't notice at the time.

Do you happen to know--I think when I was first recording for ACX, I read somewhere that the allow you to re-submit a book only once. If they reject the second version, you can never submit that book again. Do you remember whether that's the case? If so, I need to make it really perfect.

[Trebor]

Any idea what that wind noise could be? I guess it's possible it's microphone noise.
But if it's coming and going, that's the signature of HVAC or Air Conditioning ...

It look electrical: the noise above 16kHz is attenuated when the person is speaking,
& there is virtually no noise at 900Hz ....

IMO hiss is electrical.png (594.23 KiB) Viewed 1355 times

download/file.php?id=25192

[kozikowski]

I read somewhere that the allow you to re-submit a book only once.

That's a little severe, but it wouldn't surprise me. Typically, they only complain about one thing whether your presentation has multiple problems or not. It's not their job to troubleshoot your studio.

We should note the alternative to home recording is not stop reading. It's read in an actual sound studio with a recording engineer. More than one poster is on the forum because they stopped using a successful sound studio and decided to read at home...and couldn't.

I've been recording books for some time, and have 6 or 7 on Audible at present.

That makes you the unicorn. Usually somebody with that severe a problem just fails first time out. No casual home user ever passes ACX Noise. It's severe. -60dB means background noise has to be 1000 times quieter than your voice.

You really can't hear that noise in real time?

It look electrical: the noise above 16kHz is attenuated when the person is speaking,
& there is virtually no noise at 900Hz ....

I noticed that odd sound signature. Noisy microphones or microphone interfaces tend to be "rain in the trees" sound without lumps and bumps in the tones. It's also possible this is computer fan noise—a computer is warming up after a long time in use and deciding to cool itself. I have a machine which works like that. A half-hour into heavy use and I can hear a low-volume rushing whistle as the fans kick in.

In any event, because you are a unicorn, you know how to fix this—how to read successfully. Repeatedly read until you get a clean chapter. Do pay attention to the timing of the failures. Are they always the last chapter after long sessions?

It's also good you can hear the failures. There have been posters with bad speakers or headphones who couldn't hear the problem. Those people are in serious trouble.

Koz

[kozikowski]

We can continue to troubleshoot with you. The forum record is Ian who just wanted to record audiobooks from his apartment in Hollywood. 39 forum chapters and over a year.

I forget his name, but the one before that was a guitar performer who just wanted to record his Flamenco music. We replaced his microphone system.

Koz

[kozikowski]

Found it.

The second longest post in forum history is by Bruno in Portugal. He wanted to record Flamenco guitar on his computer. That was the whole job. 18 forum chapters over three and a half months.

Koz

[kozikowski]

No casual home user ever passes ACX Noise. It's severe. -60dB means background noise has to be 1000 times quieter than your voice.

Ch 6 Raw background noise is 100 times quieter than your voice.

Koz

[fredericamg]

You guys are the greatest. Thanks for being there.

Sounds like there's really no way to fix the problems in this chapter; I'll need to re-record it.

The reason for the unicorn might be that I used to record in a home studio in Maryland, and now I'm recording in a home studio in Tennessee. It's the same equipment, but a different room.

HOWEVER I think I recorded both Chs 5 (fine) and 6 (awful) while still in Maryland.

Today I'll explore later chapters, and see whether the problem appears and disappears.

I bought my equipment in Dec 2010, following the advice of someone who'd seen a YouTube I posted and spotted a number of problems right away. I bought what he recommended:

Behringer C-1U Studio Condenser Microphone with USB Interface
(Dynamic would have been better, right?)

Behringer HPS5000 Studio Headphones

(and I'm currently using Audacity 2.3.3)

Thanks for helping me out. I'll let you know later how chapters 8, 9, 10 etc sound.

Incidentally this is my book "First Fruits", https://www.amazon.com/First-Fruits-Pra ... 155725611X
It's a one-reading-a-day book, for 40 days. Originally I had 10 chapters, 4 "days" per chapter. Then I realized that would be hard for a listener to navigate if trying to find a particular day (esp while driving). So after ACX rejected it (voice too quiet, noise floor too noisy), I divided it into 40 separate, short chapters.