@ BuckGodot
write down or screen grab the settings.
On a Mac, it’s Shift-Command-3 for a whole screen and Shift-Command-4 to draw a box around the work.
I’m not sure how to do it on Windows.
Koz
Windows Snipping Tool
Start > All Programs > Accessories > Snipping Tool
Koz
Hi, Steve. It’s great to finally see an RMS normalization tool for Audacity. I’m curious about some discrepancies I’ve observed in the results from the RMS normalization plug-ins in Audacity and the Linux command line tool “normalize” (man page info: AUTHOR Chris Vaill <chrisvaill@gmail.com>). I use Audacity on Linux, and have several books on Audible that I’ve narrated through ACX. All of those have passed muster in the ACX quality check upon upload. But my method is to export from Audacity to a 16-bit .wav file and then normalize it and do further CLI processing from there (such as re-encode to .mp3).
Is it possible that Audacity alters the RMS normalization level upon import and export? For example, if I normalize some audio using the rms-normalize.ny plug-in with it set to -20 and then export it to .wav, and then use the CLI normalize command to test its RMS normalization level, the reported level is -12.4488 dBFS with a peak right at 0 dBFS. If I then use the CLI normalize command to change the file to what it thinks is -20, it reports that it applied an adjustment of -7.55dB to result in its report of -20.0000dBFS RMS with a peak at -7.5509dBFS. Import that same .wav file with no further changes back into Audacity and the rms.ny analysis tool reports the level at -27.5512 dB.
What might be the explanation for these differences? I’m happy to provide before and after audio samples if that might help.
Thanks,
Mark
Moderator note: URL removed
If the files are stereo, they may handle RMS measurement differently from Audacity.
Audacity calculates the square root of the mean of all (squared) samples (both channels), which in my opinion is the correct way to measure stereo RMS, but is not the only way.
Hello!
I’ve tried everything to add RMS normalize to a macro. I updated everything and added the .ny file to the plugin section but I just cannot find it when I’m trying to insert a command in my macros section.
Can anybody help me with this?
Do you see the effect in the Audacity Effects menu? Are you able to use the effect manually (not in a Macro)?
Steve,
I’m interested in the math of RMS Normalize. Do you run through all the samples, square them all, add the squares, then take a square root of the sum, then use that value to normalize?
Can you clarify the math, help me get my head around this? And if there’s an article that explains this (for audio newbies), I’d appreciate a link.
Thanks in advance for any guidance you might have.
– Chas
Close.
- Run through the samples
- square all of them
- divide by the number of samples (to get the “mean square”)
- take the square root (to get the “Root Mean Square”)
Then use that value to normalize.
More info: Root mean square - Wikipedia
In the latest version of this plug-in, most of the heavy lifting is actually done by Audacity rather than in the plug-in. The plug-in asks Audacity what the RMS is, and Audacity passes that information back to the plug-in. All that the plug-in then needs to do, is calculate the amount of amplification (based on the RMS level) and apply it.
If I recall correctly, older versions of this plug-in actually calculated the RMS within the plug-in, which is not so fast and requires a lot more RAM.
Steve,
- Run through the samples
- square all of them
- divide by the number of samples (to get the “mean square”)
- take the square root (to get the “Root Mean Square”)
Then use that value to normalize.
Ah, got it. So once you have the Root Mean Square, do you reverse the math to come up with a scaling factor, multiply all the samples by that scaling factor?
I got the reverse math suggestion from this page, wasn’t following:
So once I have the R (which you described), do you invert to come up with “a”, then multiply all the samples by a to normalize? Or am I still missing something?
Side note: Thank you very much for taking the time to answer a newbie question…
– Chas
It’s pretty easy really. Let’s put in some arbitrary numbers to see how it works.
Converting between linear levels and dB is probably the trickiest bit, but we only use this for setting the target level. We could just as easily specify the RMS level as a linear value in the range 0 to 1. For completeness, these are the conversion formulae:
dB = 20 * log(linear)
linear = 10 ^ (dB / 20)
So let’s say that we are aiming for a target RMS level of 0.5 linear (about -6 dB), but our actual, measured level is 0.2 (about -14 dB).
If our measured RMS level is 0.2, then we could scale it (amplify it) up to an RMS level of 1.0 by multiplying every sample by 1/0.2
But we want to amplify it to an RMS level of 0.5, not an RMS level of 1.0. Obviously 0.5 is half of 1, so to scale from 0.2 to 0.5, we need to amplify (multiply) by 0.5 * 1/0.2 = 0.5/0.2
In other words, we multiply each sample value by ( ÷ )
Steve,
Thank you so much. That was an incredibly clear explanation. Took me a bit to reread the math, til it sunk in, but I get it now. All very interesting.
– Chas
Steve,
If I do an RMS normalization, then do a Peak normalization on the results, the RMS normalization changes to the point where it no longer passes the ACX Check that it passed before Peak was applied.
Is there a mathematical best practices to combine RMS and Peak so both pass ACX Check? Do I first check for peak value, then use that in my RMS calculation in some way?
Chas
That is to be expected. The RMS normalize amplifies the audio to the specified level (based on the RMS level), and then Peak normalizing amplifies it again to a different level (based on peaks), so the RMS normalization has been overridden.
I’m guessing that after RMS normalizing, the peak level is too high. Is that correct?
You’re not following Audiobook Mastering.
RMS Normalize sets the overall loudness and then Limiter (not peak normalize) reduces only the peaks so they pass ACX.
If the eventual goal is audiobook processing, there are some real-world problems that should be addressed.
Past the obvious one of setting loudness with RMS-Normalize and then adjust the peaks with Limiter, you also should get rid of rumble and low pitch tones before those tools. That’s what Equalize does. It’s called Filter Curve in the latest Audacity.
Home Microphones like to create their own rumble and low pitch noise in addition to picking up room noise. Those noises can throw off RMS Normalize and Limiter.
After you finish mastering you may find that the background noise is too loud. Home performers never pass noise. It’s hard to get the background noise 1000 times quieter than your voice.
Koz
Steve: I did RMS first, then Peak, so Peak was perfect, but RMS got too low. But…
Koz: Thanks for that link. I’m new to this, had not read the Audiobook Mastering post. I’m trying to follow the math of all this, the page was helpful. Learning about limiters now. Appreciate both yours and Steve’s patience as I learn.
– Chas
So applying peak normalization pushed the level down. That means that the peaks were too high, so what you need to do is to reduce the peaks without affecting the RMS (or at least, not affecting the RMS too much. To do that, use the Limiter to reduce the peaks. To minimize audible effects of the Limiter, use the “soft limit” option.
Note that limiting will have a small affect on the RMS level, but unlikely to have a big enough effect to be a problem.
Limiter > Soft Limit is the magic one.
Anybody with a ruler, an adding machine and strong coffee can figure out RMS.
How do you intentionally distort a voice wave so the peaks never exceed a set value but without changing overall loudness (RMS) significantly—and do it so nobody can hear the change or tell what you did?
There was an early peak processor called “Leveller.” It was OK, but it used brute force techniques that weren’t always satisfactory. It’s still available in the tool kit under Effects > Distortion.
Koz
Hello everyone,
After about two hours clicking around in circles…here goes with a very low-level question. How do install RMS Normalize?
I have been up and down this link: https://manual.audacityteam.org/man/installing_effect_generator_and_analyzer_plug_ins_on_windows.html#nyquist_install
However I cannot for the life of me find where I can actually GET this Nyquist Plug-In Installer that is repeatedly mentioned. Does anybody have a link?
I tried to do it manually per the instructions, but when I go to Library/Application Support I don’t see Audacity listed…is there somewhere else it could be hiding? I tried searching and clicking through everything…
I am on latest Mac Catalina 10.15.3 and Audacity 2.3.2.
Many thanks in advance,
Richard
Since 2.3.1 it’s part of Audacity in the Tools menu - go to Tools > Nyquist Plug-In Installer
WC