I am wondering if it negatively impacts the audio to repeat an effect (with all the same settings) like equalization or RMS normalize, etc? I opened an audio file that I had worked on previously, but couldn’t remember if I had done all the steps for production, so I ran them again, just in case. It didn’t look like the waveform changed much, so I figured I must have done it before. Is that bad?
Also, if I repeated the functions on this chapter of my audio book, should I now repeat them on all the other chapters to make them match???
Normalization is a special case and NOTHING happens if you apply it twice with the same settings.
And in general, multiple volume adjustments are “harmless” as long as the changes aren’t too extreme and as long as you don’t push the levels into clipping (distortion) and then export to a format that can clip.
If you save-as an AUP project (or floating-point WAV) you’ve got virtually unlimited dynamic range and lots of precision so you can make extreme volume changes without damage.
Of course, if you do things like boost the bass twice or add reverb twice you’ll get twice the effect.
RMS Normalize and Limiter don’t do anything if they’re not needed, but Equalize will double apply. If Equalize reduced 100Hz by 3dB (for example) applying it twice will reduce 100 Hz by 3dB more. In the specific case of Low Rolloff for Speech, you may get away with that because the tool is designed to have minimal impact on audible speech.
should I now repeat them on all the other chapters to make them match???
Listen. If you have good speakers or headphones (recommended for any production work) you may hear a timber change in your voice if you double apply equalization.
In all cases, however, an uncorrected reading will almost certainly not pass ACX Check.
There’s a more exotic way to tell, too. Drag-select some of the performance and Analyze > Plot Spectrum. A raw reading, particularly with a home microphone will have significant energy below (to the left of) 100Hz. Low Rolloff is designed to prevent that.
Fair Warning the three tools in Audiobook Mastering 4 are designed to be used together. They are a suite, a “harmoneous grouping.” More crudely, they mop up after each other.
Low Rolloff is there so RMS Normalize and Limiter don’t get faked out by the rumble sounds in many home microphones. RMS Normalize naturally produces peak sound overload which Audacity can manage OK but can’t be exported. Limiter is designed to gently solve peak overloading.