Trying to get RMS within spec without making Peak too high!

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Trying to get RMS within spec without making Peak too high!

Permanent link to this post Posted by alleyandy » Wed Feb 08, 2017 6:41 pm

Hi All,

I'm using the following to record the voice track for an audio book:

Recorder: Zoom H5
Mic: Shure SM58
Record Format: one-track WAV
Editing: Audacity 2.1.2
Added Plugins: ACX Check, stats

The recordings seem to be coming out OK, noise is low, but the volume is not high enough to pass ACX specs.

The problem I'm having is when I increase RMS high enough for ACX, it brings the Peak up too high, so that fails.

I'm confused about what I should use to increase the RMS (Amplify? Normalize? Compressor?) and how to keep the Peak within proper range.

I'm also not sure what order to work in. Do I lower the peaks first, then amplify? Or amplify then reduce peaks? Or is there a way to increase RMS without increasing peaks?

Sorry that these are probably simple questions for someone experienced. I've done a lot of reading, but haven't been able to figure this out.

Thanks for your help!

ACX Check Before.jpg
ACX Check before I do anything to mess things up!
ACX Check Before.jpg (46.82 KiB) Viewed 245 times
alleyandy
 
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Re: Trying to get RMS within spec without making Peak too hi

Permanent link to this post Posted by alleyandy » Wed Feb 08, 2017 7:31 pm

OK, so it's like some kind of magic- I research for hours (days?), finally post a question, and within minutes find my own answer!

Sort-of.

So, here's what I've found.

1) Import the WAV file into Audacity.
2) Run ACX Check.
3) Find the RMS too low.
4) Apply Amplify to bring RMS up.
5) Run ACX Check.
6) Find Peak too high.
7) Apply Limiter to bring down peaks.
8) Run ACX Check.
9) It passes!

So now, the only question I think I have is...

How can I get the RMS level fairly close from clip to clip?

For instance, here are the levels for the first 7 files:

01 -19.6 dB
02 -19.0 dB
03 -19.8 dB
04 -18.8 dB
05 -20.3 dB
06 -20.8 dB
07 -21.7 dB

Are these close enough so that people won't have a volume problem from clip to clip?

Or is there a way to being them all closer together? If so, what range should I be shooting for? -19.8 to -19.0? Less? More?'

I just don't want people blowing their ears out, or having to adjust the volume, from chapter to chapter...

Thanks!
alleyandy
 
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Joined: Wed Feb 08, 2017 4:50 pm
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Re: Trying to get RMS within spec without making Peak too hi

Permanent link to this post Posted by steve » Wed Feb 08, 2017 7:45 pm

alleyandy wrote:Are these close enough so that people won't have a volume problem from clip to clip?

2dB is not a big difference, but test it:

Import tracks "02 -19.0 dB" and "07 -21.7 dB" into a new Audacity project (they will import as two tracks, one above the other).
Use the Mute/Solo buttons to switch from one to the other. Is one noticeably louder than the other?
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)
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Re: Trying to get RMS within spec without making Peak too hi

Permanent link to this post Posted by alleyandy » Wed Feb 08, 2017 8:20 pm

Hi Steve,

Thanks for your reply.

I tried your suggestion, and I can't tell there's a difference between the clip that's at -19 dB and the one at -21.7 dB.

I also compared -18.8 dB and -21.7 dB, and they sound pretty close to me.

Of course, I'm listening to them over the voices in my head, but still.... :?

One thing I just found, as I'm going through all 22 clips, is that one (so far) had an RMS that was still too low after the first pass of Amplify/Limiter, so it needed another round.

Does that degrade the resulting quality, or is it OK to do two rounds of Amplify/Limiter?

Or is there a better way?

This is all fascinating to me, since I've never really paid this close attention to the technical specs of audio. I've always just listened and, if it sounded good to me, I was done!

Thanks again!
alleyandy
 
Posts: 4
Joined: Wed Feb 08, 2017 4:50 pm
Operating System: Windows 10


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