Microphone picking up neighbor's AC

Special Interest Groups Audiobook Production
21

Don’t fall in love with the MP3 format. MP3 adds compression distortion to your voice and it gets worse the more production you do. ACX demands submission in MP3 format, but that’s a business decision, not a sound quality one. They have to store your work on their servers which they have to pay for. So small sound files are financially desirable.

You are required to submit MP3 at 192 quality or higher.

https://www.acx.com/help/acx-audio-submission-requirements/201456300

Say you get ready to submit a work which you have prepared at 192 quality, but you notice a sound glitch or damage somewhere. Easily correctable, so you fix it and export the corrected work at 192. The work isn’t at 192 quality any more. It’s some lower number. You can’t make an MP3 from an MP3 without increasing the sound damage.

This can be a big problem because ACX is going to resample your work for their products and services on top of whatever you did. So the quality goes down again.

Do all your work at WAV 44100, 16-bit mono. Export a WAV of each RAW reading as a safety backup. If you need to use it for something, make a copy and edit that. Don’t depend on Audacity Projects for everything. Scan through the forum for postings about not being able to open a valuable project.

Make a WAV of your final edit and only then make the 192 quality MP3 for submission to ACX.


So make one of these exactly like you’re going to read it. Forget the hum for the present.

http://www.kozco.com/tech/audacity/TestClip/Record_A_Clip.html

Pick a chapter of a book you like or whatever work you’re going to read for real. Don’t apply any processing other than maybe cut out a mistake or combine two sentences to come in under the time limit. Don’t ad-lib. Follow the instructions and go down the links. They’re very short.

Koz

22

Next time an adjacent ac kicks in, I’m going to throw the mic under some coats and quickly get a recording.

That said, koz, that recording sounds pretty much completely free of humming. However, I have a couple questions.

I have a low rolloff for speech preset in Audacity … come to think of it, probably from an old post of yours. However I’m not really savvy on how I’d go about messing with it to match the setting you used in your recent tweaking of the humming audio. Could you explain perhaps?

Regarding the Limiter, I’m also not really aware of how I’d use it; mine doesn’t have a “Soft Limit” preset, only a series of sliders. Again if you could help with this, I’d appreciate it.

So, when I’m recording, the ac obviously comes and goes. Let’s say about a quarter to one half of each hour recorded will have that humming. Will the fact it’s inconsistent interfere with my ability to have a cohesive product? For example, using presets and tweaking sliders for a recording that has the humming throughout sounds good in theory, but will those presets mess with the “clean” parts - cause an over correction of sorts? Pardon my lack of knowledge.

And finally, I ran a “humming” sample through some software called Levelator. I saw this recommended by a relatively successful ACX recording artist, and it’s actually how my 15 minute sample for my first book got approved. Levelator managed to almost completely remove the humming, though it’s still faintly noticeable during speech. Can you tell me whether or not I should use this software in instances such as this? I only ask because while there is definitely consistent reduction in hum with your presets, koz, I hear a faint echo/tinniness to my voice that isn’t present in the Levelator output. It has its own problems, like the hum being just barely discernible at the end of spoken lines. Just curious what your stance on Levelator is, if you’ve heard of it.

One final thought, promise - if I do abandon Levelator, I’m going to use your Mastering guide, koz. I was checking out your guide last night and was having some issues, but we can discuss those once we’ve come to more concrete place regarding the humming.

Now to wait for the ac again. Thanks so much as always guys.

23

I just noticed this, sorry! I’ve made a mental note of your suggestions. I am new enough to recording that I really don’t have much raw data at the moment, but the things I have and intend to use, I’ve converted to .wav files in mono format.

Do you want another sample from me?

24

Did we ever find out which Audacity you have? The latest one is 2.3.2 and you can get it from here.

I’m also not really aware of how I’d use it; mine doesn’t have a “Soft Limit” preset

So you may have an older Audacity with tools missing.

Let’s say about a quarter to one half of each hour recorded will have that humming.

As in the last post, forget the humming for a while. That’s not the only problem you’re going to have and I want to address Everything Else.

When you get Audacity 2.3.2 installed, you will also need the ACX Check tool to inspect your submission and RMS Normalize which doesn’t come (yet) with the standard Audacity.

RMS Normalize appears under Effects, but ACX Check appears under Analyze. This can be confusing.

Scroll down to Installing Plugins.

https://manual.audacityteam.org/man/customization.html

Koz

25

Because it was requested, here is the mic recording (with the ac running) while covered in blankets.

26

I’ve updated to the latest version, installed RMS normalize/still have the LF rolloff preset, as well as ACX check. I still don’t have anything for Hard Limiter, however.

27

This still shows big peaks at 59 and 120 Hz, so assuming that the microphone was well insulated (acoustically) from both the air and the floor (low frequency vibrations travel very easily through floor joists), it would appear that the interference is electrical.
If you have doubts about how well insulated the mic was from the floor, please rerun the test.

The frequencies I’m referring to can be seen in “Plot Spectrum” Plot Spectrum - Audacity Manual
I amplified the track first so that the spectrum is clearer:

Untitled.png
Is there any difference (better or worse) if the laptop is plugged in?


Hard Limiter has been replaced with a (much better) Nyquist Limiter. See: Limiter - Audacity Manual

28

I still don’t have anything for Hard Limiter, however.

It’s Soft Limiter and it’s been included in Audacity for at least the last two versions.

Effect > Limiter and you should be able to find or make a panel that looks a lot like this.


Screen Shot 2019-08-06 at 11.15.38.png
Those are the settings for Audiobook Mastering.


There is no separate soft limiter.

Find it?

Koz

29

I forgot to mention, I snapped my finger at some point during that recording. One of those peaks is probably from that. And it’s possible I didn’t insulate it very well from the floor, it was just sitting on a tv tray swaddled in blankets. I will have to rerun the test, I think.

And every time I’ve recorded the AC hum, the laptop has been on battery power only.

30

I see it now, thank you!

31

This is probably the best I can do in terms of insulation. No extra crap from me, just “silent” room noise with the ac running.

32

I presume that you can still hear the hum in that?

I suggest that you try a test recording with the computer plugged into mains power. I would expect it will either be worse, or make no difference, though there’s a slim chance that it could reduce the hum.

33

Oh yes, however distant, I can still hear it.

Further testing will come later, I think. Thanks for your help so far - what can you suggest based on what we know now, or, should we wait until I have a sample with the laptop plugged in?

And koz, would you like me to record a 20~ second sample of me reading a book for you, or something a little longer? I would enjoy going over the proper steps to make my audio ACX-compliant and consistent. Speaking of that, do you know about how much variance they allow in terms of RMS/dB between chapters? What I’m working on for ACX now sounds pretty consistent in terms of finished product, chapter-to-chapter, though there are very slight variances in these levels.

34

Yes.
Try to ensure that your settings are identical in a plugged in / not plugged in pair of audio samples so that we can do a meaningful comparison.

35

And koz, would you like me to record a 20~ second sample of me reading a book for you, or something a little longer?

Since you will be producing a mono WAV instead of MP3, 20 second sound clip is all that will fit on the forum. If you go longer it will cut you off.

Nobody cares if it ends perfectly on a word, but the clip should be theatrically correct. If you want, read longer and and cut it off at 20 seconds. Full-on storytelling mode. Have you listened to an audiobook? If you haven’t, you should. This is where I post a sample but I can’t since I’m not at home. Later.

Most public libraries will let you take one out and listen to it.

ACX has two tests. The first is a cousin to ACX Check where they test loudness, background noise, etc, physical things, but the second is Human Quality Control. That’s the one where they test whether or not you can read out loud and whether someone is likely to buy it if you do.

I would enjoy going over the proper steps to make my audio ACX-compliant and consistent.

We’ll get there. This test should be unprocessed. Record it, chop it off at 20 seconds and post it. We can’t take effects out of a sound file, so if you make a finished presentataion and do something wrong, neither of us will have any idea what to do. From the raw reading, we can tell you what to do.

We are following the recommendations and requirements of ACX.

https://www.acx.com/help/acx-audio-submission-requirements/201456300

And we have a pretty good track record of getting people published.

Koz

36

Koz, I’ve listened to hundreds of hours of audiobooks. I’ll get you a sample when I’m home tonight.

37

Here’s an unedited sample of me reading for you, Koz.

38

And, finally, the mic swaddled in a blanket, plugged in to the laptop, which is plugged in to the mains, with the neighbor’s ac running.

39

Here’s an unedited sample of me reading for you, Koz.

That came out well. First three sentences and confirmation 2/3 down.


Screen Shot 2019-08-06 at 19.58.50.png

I applied our three audiobook mastering tools. It took me 25 seconds. I counted.


This is the abbreviated version (in yellow).


Screen Shot 2019-08-06 at 20.04.34.png
Screen Shot 2019-08-06 at 20.04.34.png1426×282 34.9 KB

Please note that selecting a whole track has changed at least three times in recent memory. I think in 2.3.2, there is an actual SELECT button on the left that does it.

And this is the full instruction set with all the notes.

It even passes noise by the fuzzy rule of quieter than -65dB. You win. If you produce all the works at that volume, this may be all you need.

I think one of the questions was setting the overall volume. That’s what RMS Normalize does. So your volume can wander a little during the live presentation and Mastering will bring you back automatically.


Peaks need to be quieter than -3dB.
RMS (Loudness) needs to hit between -18dB and -24dB.
Noise needs to be quieter than -60dB.


You still have to patch fluffs and sneezes, etc. That’s basic editing, but if you read like that through the process, it should be good to go.

That’s my opinion. Others may post.

Koz

40

There is a note about listening. It’s not fair to go “Diving For Noise.” Set the speaker or headphone volume for normal voice during the show and then roll it back to the noise at the beginning without changing anything. The noise at the beginning of the clip should be very nearly completely gone.

Koz