They can all be perfectly accurate, but you do have to define your terms.
https://forum.audacityteam.org/t/measure-between-23db-and-18db-rms/32770/16
We designed ACX-Test as an add-on to Audacity in order to simulate the technical specification robot you’re going to hit when you submit to ACX.
http://wiki.audacityteam.org/wiki/Nyquist_Analyze_Plug-ins#ACX_Check
The tool appears under Analyze and the first three values are hero. The tool will tell you if you passed and by how much.
Noise can be measured a number of different ways. Like it says in the brief, it’s what happens when you stop talking. You can measure the peaks, that is, watch the sound meters (assuming you have them set for good enough sensitivity) and get a rough reading from that. That may be what the other program is doing. That’s easy to do, but not particularly useful.
You can measure the RMS value of the noise. Without knowing what that is, it’s the way both ACX-Check and ACX submission work. It’s the amount of energy in the noise. As a rule you can’t get there by looking. You have to have a tool measure it for you. Audacity has a manual tool called Analyze > Contrast which will tell you many of these values, but it’s much more difficult to use. ACX-Check is just so much easier.
Once you get the energy or RMS value of the noise, you don’t have to stop there. There are variations on noise measurement. There is a legal one which applies the “A” curve to the measurement. You can have a thunderstorm and bats flying around the house (work with me here) and some noise instruments will tell you there is a terrifically high noise value—and you can’t hear a thing. That’s because the bats are too high and the thunderstorm is too low. The “A” curve ignores any noise humans can’t hear. That’s the one hazardous noise environment measurements use.
But ACX doesn’t use that one. They use the one that can hear bats and metro-busses, so it’s good to know that. We have a trick you can use if you almost but not quite pass noise and could use a little boost. We have a metrobus filter.
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You should know that twice now I was able to set up a simple microphone arrangement in my very quiet third bedroom and produce an ACX Compliant voice clip by simple adjustment of the volume. So no, laundry lists of corrections, adjustments, filters, effects and manual patching are not needed for a generic ACX posting if you’re doing a reasonable job with good equipment. I will admit I probably could not read a book like that, but I just wanted proof of concept.
So that’s what you’re doing.
I designed a forum voice test format.
http://www.kozco.com/tech/audacity/TestClip/Record_A_Clip.html
This gets everything we need into one pass and posting. We can usually tell you how to get to ACX submission from where you are and how to tune the corrections if needed. Please note we can’t take corrections out of a clip, so submitting a fully corrected clip and asking, “What’s wrong with it,” doesn’t go anywhere.
Koz