English version of the ACX readings.
Peak. Look at the blue waves on the timeline. The very tips of the waves are never allowed to go all the way up or down. That’s overload (1.0 on the timeline – 0dB on the bouncing sound meters). That can cause audible crunching and distortion. ACX doesn’t even want you to get close, so that’s their -3dB (70%) limit.
RMS. Loudness. Root Mean Square is a standard electrical measurement which, when applied to audio, happens to work out to loudness. RMS should be between -18dB and -23 dB.
Noise. How loud is the show when you stop talking? This can be a combination of dogs barking next door, air conditioner noise, and the ffffffff noise the microphone is making. All of it lumped into one number. Noise should be quieter than -60dB.
And yes, it’s perfectly possible to have a performance that won’t meet all three at the same time. It’s pretty common for home readers.
It’s also possible to pass ACX-Check and still fail acceptance. If you got there by heavily processing and beating your voice to death, the work will fail Human Quality Control. The voice is distorted and the failure is “Overprocessing.”
Koz