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Old 01-22-2021, 08:57 AM   #1
mfspeaks
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Default Issues with RMS and Peak levels

Hello

I am a newbie on Reaper and am hoping to produce audiobooks for ACX. So, I guess a newbie to the world of audiobook productions also.

I have spent some time trying to understand reaper. I have also recorded a couple of tracks; about 1 - 1.5 mins long, each time with a slightly different gain. Have converted the wav files to mp3s.

Some of ACXs submission requirements are:

Each uploaded audio file must
*measure between -23dB and -18dB RMS and
*have -3dB peak values and
*a maximum -60dB noise floor

I have run my mp3s against the ACX check on Audacity.

Some results are:

Peak level: -3.17 dB (Pass)
RMS level: -23.16 dB (Fail)
Noise floor: -66.30 dB (Pass)

Another one at a slightly higher gain:

Peak level: -2.47 dB (Fail)
RMS level: -20.27 dB (Pass)
Noise floor: -74.22 dB (Pass)

Yet another at a slightly different gain:
Peak level: -5.85 dB (Pass)
RMS level: -26.16 dB (Fail)
Noise floor: -67.87 dB (Pass)

I have even tried adjusting the volume slider in item properties. But the same problem. If the Peak level passes the RMS level fails or vice versa,

I have read several forums but not much help out there for audiobook producers. There is stuff more for musicians.

Can someone suggest how I can adjust the peak levels without affecting the RMS level or how I can adjust the RMS levels without affecting the peak levels?

Thanks
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Old 01-22-2021, 09:24 AM   #2
DVDdoug
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Quote:
Can someone suggest how I can adjust the peak levels without affecting the RMS level or how I can adjust the RMS levels without affecting the peak levels?
The Audacity website has a Recommended Audiobook Mastering Process that will nail your levels every time.

It's simply a matter of setting your RMS levels first ("RMS normalizing") followed by limiting to make sure your peaks are in-spec. Limiting has very little effect on the RMS so everything should be good.

MP3 compression can often slightly increase the peak levels but the recommended -3.5dB settings gives you 0.5dB of safety margin.

Last edited by DVDdoug; 01-22-2021 at 09:31 AM.
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Old 01-22-2021, 09:31 AM   #3
Allybye
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I would suggest just going sith the increased gain setting (gour middle example) and then adding a little compression with a threshold of say -15dB and a 2:1 ratio. ....or a variation on that.

That will keep the noise floor similar, not change the rms level much but hold back the peaks a bit. If not held back enough increase the ratio a little.

A limiter will do similar but can be a bit agressive.
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Old 01-22-2021, 09:33 AM   #4
Allybye
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You were quick DVDdoug.
I was not aware of that Mastering process so that is probably a better method!!


Edit now seems to be at link https://wiki.audacityteam.org/wiki/Audiobook_Mastering
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Old 01-22-2021, 02:52 PM   #5
mfspeaks
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Thanks DVDdoug and Allybye. Very useful.

So tried both your suggestions...hence taken me so long to reply. Trying all variations and combinations. So here goes:

As I mentioned I am working in reaper.

When I rendered my raw recording as 16 bit WAV (as per audacity instructions and also ran the various effects of filter curve, loudness normalization and limiter and the ACX check)
I got the following results:
Peak levels: -3.80 (Pass)
RMS levels: -20.37 (Pass)
Noise floor: -90.21 warning (too low - dead silence sounds unnatural)

I ran an ACX Check in audacity on the same file as a 24 bit WAV (after adding a little bit of compression with a threshold at -15dB and ratio of 2:1 on my raw file in reaper and also including the audacity effects of filter curve, loudness normalization and limiter)
Got the following results:
Peak: -3.64 (Pass)
RMS: - 20.35 (Pass)
Noise floor: -88.03 (Pass - barely I would think, phew)

And finally tried something else:
I ran an ACX Check in audacity on the same file as a 24 bit WAV (after adding a little bit of compression with a threshold at -15dB and ratio of 2:1 on my raw file in reaper but this time without the audacity effects of filter curve, loudness normalization and limiter)
Got the following results:
Peak: -3.68 (Pass)
RMS: - 22.60 (Pass)
Noise floor: -73.38 (Pass)

So now my new questions:
*Why such a big change in the noise floor with the audacity effects?

*Also another bigger challenge I ran into was when I exported these wav files to mp3s (File-export-export as MP3) (that's another ACX requirement) and then ran an ACX check, the Peak levels and RMS levels failed miserably all 3 times.

So now I have a new problem. I am not familiar with audacity at all. So I guess I will have to do some homework. But any help or suggestions are welcome. Thanks
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Old 01-22-2021, 03:52 PM   #6
DVDdoug
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Quote:
Noise floor: -90.21 warning (too low - dead silence sounds unnatural)
That is unusual without some "artificial" noise reduction. It's also unusual to pass noise with a recording that wasn't made in a soundproof studio.

And, RMS normalization almost always ends-up boosting the levels which boosts the noise, and it usually pushes the peaks over 0dB.

Quote:
without the audacity effects of filter curve, loudness normalization and limiter...

...
So now my new questions:
*Why such a big change in the noise floor with the audacity effects?
Low frequency noise is pretty common and the "filter curve" knocks it out without damaging the voice range. Our ears are not as sensitive to the low frequency noise but ACX uses a flat (unweighted) noise measurement.

Quote:
*Also another bigger challenge I ran into was when I exported these wav files to mp3s (File-export-export as MP3) (that's another ACX requirement) and then ran an ACX check, the Peak levels and RMS levels failed miserably all 3 times.
That's strange... MP3 should have almost no effect on the RMS level and it should only slightly change the peaks.

Quote:
So now I have a new problem. I am not familiar with audacity at all. So I guess I will have to do some homework. But any help or suggestions are welcome. Thanks
You should be able to do everything in REAPER, except RMS normalization might take an extra step or an extra plug-in. And, you still need Audacity if you want to use the ACX check plug-in.

Or of course, you can do all of your recording & editing in REAPER, render to WAV, and then master in Audacity.
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Old 01-22-2021, 06:31 PM   #7
jrk
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Quote:
Noise floor: -90.21 warning (too low - dead silence sounds unnatural)
Quote:
Originally Posted by DVDdoug View Post
That is unusual without some "artificial" noise reduction.
I suspect there's some of yr actual silence in there - gaps between items?

This is the kind of thing that a bit of "room tone" (a recording of just the background noise), or a dose of pinkish noise, can help with.
__________________
it's meant to sound like that...
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Old 01-22-2021, 08:11 PM   #8
mfspeaks
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Thanks DVDdoug.

jrk: I do have room tone in already...but thanks for the insight.

Will tweak things a bit more....and see what happens

Last edited by mfspeaks; 01-22-2021 at 08:30 PM. Reason: edited
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Old 08-11-2021, 12:45 PM   #9
TheWarrant
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Default I'm a newbie as well

Since you're in the Reaper site, I'm thinking you're using Reaper. I too had a lot of questions about getting my audio files to ACX requirements. I too had issues trying to measure the -18 to -23 dB RMS levels. I was using Audacity initially, then went searching online for a better DAW. I found Reaper and it blew my mind - I couldn't figure out up from down - didn't even know where to start because I hadn't used a DAW before. The learning curve is STEEP because there's SO much that Reaper can do, and it's NOT geared for audiobook recording, it's built for SO MUCH MORE. I am NOT getting paid by anyone, or getting any returns from what I'm about to say --- I found a guy, that teaches an online course of how to do audiobooks, using REAPER. Amazing - he shows how to use Reaper and 'get around' a LOT of obstacles I was facing. He uses Reaper exclusively for his work in audiobooks (over 20 now with NO returns for QA issues) AND his work in documentary films ... he's a long-run documentary film producer and director. The guys class (online) is amazing. His name is Paul Jenkins - his online class is available on UDEMY, and wait for the SALE, because it's normally like $200 for the class (85-lessons), but I got it on sale for $16 .... yep, $16. He takes you through everything - how to set up Reaper, doing Punch & Roll recording, marking your chapters, setting the Special Effects for Gate, Equalizer, COmpression, and how to use aftermarket products (free) to set your normalization, and to get your peaks limited to less than -3dB and the range set to between -18 & -23 dB ..... I'd be lost without this guy.
Here's a link to the course - OH, I just checked, it's on sale for $14.99. He does a LOT of 'batch processing' of files - HUGE time saver.
https://www.udemy.com/course/the-com...ration-course/

Good luck ...
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