RMS analysis/measurement tool?

Hello, does there exist a “simple” RMS measurement tool for Audacity?

I have used the Contrast analysis tool, but it is not designed for simple RMS measurements. It throws a pop-up error window when the segment of audio to be measured is completely beyond the ends of the first track in the project, making measurement impossible. This is because it is designed to compare 2 tracks, not simply measure 1 track.

All I want to do is measure the RMS amplitude of selected audio, to aid me in choosing an appropriate compression threshold. I could really use a RMS measurement tool without all the extra Contrast stuff.

…although it would be handy to have at least 2 slots (maybe 4?) in the tool, so that a person could measure 4 sections of a track (perhaps movements in a song) and then see how they compare to each other. Maybe there could even be fields in which the user can enter/edit labels for each slot that stay in the tool’s app data until he decides to edit them at a later time. (Edit: You know what, I think 8 slots would be awesome!)

The best free tool I know of is the [u]SoX[/u] stats command. But, SoX is a command line tool so it’s not quite as easy to use as Audacity.

You might try Steve’s [u]ReplayGain[/u] plug-in. It can be used to find the relative loudness of a file (not the same as RMS). The ReplayGain analysis gives you the recommended change, so a louder file will give you a negative recommended dB change, and a quiet file will give you a positive recommended dB change, etc.

Adobe Audition has a similar feature, but it’s not free and it’s now a cloud subscription program. GoldWave ($60 USD) can be “tricked” into giving the RMS volume by running the Volume Match tool, which IMO is easier than Audacity’s Contrast analysis.

I depends how long the audio is. You can write RMS information to a file using Sample Data Export if you choose the “All” header. There is a length limit of 1 million samples, so about 22 seconds at 44100 Hz.

However I think the “ACX Check” Nyquist plugin is now the simplest tool. Put that plugin in your Audacity “Plug-Ins” folder. In Audacity 2.0.6 which I understand you prefer, restart Audacity. In 2.1.1, use Effect > Manage…, enable the plugin then OK.

ACX Check will then be in the Analyze Menu. The plugin has no interface, but the RMS for the selection and much other information will be displayed in a popup.

Measuring four selections and comparing them is a feature request. Audacity can only operate on one selection at a time, with the exception that if multiple selections are labelled and a selection fully dragged over the labels, Edit > Labeled Audio can perform edits on those labelled regions.


Hi guys, thank you!

ACX Check looked interesting by the description, so I installed it. I found out via error pop-up that it has a 100,000,000 sample limit, which my current project exceeds (project is almost an hour long). I went in and changed the limit to 200,000,000 samples and tried again. It seemed to work… It spent more than a minute calculating, and then Audacity crashed and closed. I will try to see if there is anything else in the code that needs to be adjusted. I don’t know Nyquist, so I’m not sure what I will find…

That’s why it has the limit.

100 million samples at 44100 Hz sample rate is about 37 minutes 47 seconds. If your track is an hour long you can analyze the first 30 minutes, then analyze the second half.