Set Audio File between -23db and -18db

[W. Allan McLeod]

Windows 8.1; Audacity 2.0.5; .exe
I created Audio Book, 21 hours, 63 chapters, which I wish to publish on Audacity. Audacity requirement : each uploaded file must measure between -23dB and -18dB RMS. Can I set these parameters in Equalization? Other thoughts? Thanks.

[DVDdoug]

Try Analyze -> Contrast. Just select the whole file since you're not really trying to find the "contrast".

[Gale Andrews]

I've moved this to "Audiobook Production" - you'll find lots of help in the topics in this board about this.

Just to add, "Analyze > Contrast..." measures RMS but does not set levels. Contrast only analyzes a selected, single non-stereo track. I expect a good suggestion may be to use Compressor if the RMS is lower than you are trying to set.


Gale

[W. Allan McLeod]

Thanks for input; greatly appreciated.

[daringnovelist]

Is this also a good way to measure the noise floor?

When I select silent areas, I find they are -59 to -61, is that my noise floor?

Also, when I select the whole track, I come out with -21, but when I select lines of speech without silences, I'm getting readings of -19 to -16. Does that means it's too loud for the range mentioned above? or is the -21 my actual rms?

Camille

[Robert J. H.]

Is this also a good way to measure the noise floor?

That's arguable...
It's the way ACX will measure it, so it is the right thing to do.

When I select silent areas, I find they are -59 to -61, is that my noise floor?

Yes.

Also, when I select the whole track, I come out with -21, but when I select lines of speech without silences, I'm getting readings of -19 to -16. Does that means it's too loud for the range mentioned above? or is the -21 my actual rms?

Camille

First question: Is your peak already at -3 dB?
If not, the difference has to be added to your Rms values.
Example:
peak = 0 dB, then you'll have -62 to -65 dB noise floor and -19 to -22 dB speech level.

Acx will probably measure with pauses included since their usual blocksize is 60 s.
However, they will measure actual text and not the introductory titles ("Chapter") where exceedingly long pauses exist (depends on who is responsible for the measurement).

Tip: Make a trial export to mp3 (192 kbps) and re-import the file.
Make your measurements with this file, is the peak level still -3 dB?
If not, amplify the original by the difference and export again.
It's possible that the original needs a peak level of -4 dB in order to have a decoded mp3 file with -3 dB.
The Rms levels will accordingly be lower.

[daringnovelist]

Thanks, I think I was just measuring a podcast file I'd already processed in Audacity with some noise reduction, compression and normalization -- so yes, the peak levels were at -3. (Right now, I don't want to fix any files so much as I want to know how to measure them.)

Thanks for the tip on re-importing the mp3 file. This may explain some results I thought were odd when testing things with the tool they have from Librivox.

Camille

[kozikowski]

The new Contrast in Audacity 2.0.6 can no longer be used to measure noise. In order to clear up some odd results, it now ignores silent patches when it measures RMS. Tight measurements and loose, sloppy measurements on the timeline are a lot more consistent now.

One quick and dirty way to measure noise is watch the light green sound meter jump when you play the silent track. That's the RMS as interpreted by the sound meter and it will go all the way down to digital silence.

Attached is a measurement of a recent sound clip I recorded. I put the noise at about -73 or -74. Well below the -60 specification. It will jump, of course. It's measuring live audio.

You might also have to change the sound meter if yours stops at -60.

Audacity > Edit > Preferences > Interface > Meter dB Range. Set to -96 for this. You might also need to increase the size of your meters, probably a good idea no matter what. Click on the right-hand edge and pull sideways.

The RMS measurement is probably good if you get close. Their first pass testing is generally used to rapidly weed out people trying to submit hopelessly trashed recordings. If you get close enough, they go to manual review (which can take many days) and that's where they make the final analysis. They may accept it as it is.

ACX has a new (I'm guessing) trick. They will allow a 15 minute test submission so you don't have to record the whole book before finding out it's technically not acceptable.

Did you have problems with microphone hiss? Can you describe your "studio?" Do you have a "raw" clip posted somewhere? Before processing? Do have a final clip? We can give your our opinion of technical specs. You can post a ten second mono WAV file on the forum. Make sure it includes a silent patch.

http://forum.audacityteam.org/viewtopic ... 49&t=72887

Koz

[kozikowski]

Please tell me you saved the original raw recording as either WAV or Audacity Project (or both). A very common error is people write corrections on top of the capture files. If there's a problem they can't revert to the clean recordings and try again. If ACX complains about high volume (unlikely, but still) it's easier to patch that by going to the original sound files.

Koz

[steve]

The new Contrast in Audacity 2.0.6 can no longer be used to measure noise.

I don't understand your point koz. It has never measured below -60 dB.

In order to clear up some odd results, it now ignores silent patches when it measures RMS.

It has always done that.

The difference between the Contrast tool in the current version and previous versions is that the old version would sometimes measure the length incorrectly if slightly overlapping the boundary of an audio clip (see: http://bugzilla.audacityteam.org/show_bug.cgi?id=720#c3)
This means that the Contrast tool CAN now be used reliably, whereas the old version would occasionally give completely wrong readings if the selection included multiple audio clips.

The two main limitations that remain are:
1) It (still) does not measure below -60 dB (not required for its intended purpose).
2) It (still) works only for mono tracks (WCAG v2 only specifies measurements for mono tracks).
For the purposes of audiobook production, it would be better if we had a tool that could measure accurately below -60 dB and was able to handle stereo tracks (though generally mono is preferred for audiobooks).