There is no dB scale with percent waves. That’s an artist representation with the idea of eventually changing Audacity to that instead of a percent scale. Cool Edit does it that way and it would be welcome to have that display and not have to convert with a calculator. Quick, what’s -10dB in percent?
What’s your work? It’s good not go too far down the road without knowing what the poster’s show is. If it is reading for audiobooks, there is a published mastering suite.
https://forum.audacityteam.org/t/audiobook-mastering-version-4/45908/1
If you have a reasonably quiet recording environment, you can apply the three effects and out the door.
-=-
It’s 30 percent. So recommended live voice reading waveform peaks should fall roughly between 30% and 50%. That’s -6dB and -10dB on the meters. Isn’t converting fun? The percent waves are handy here because you should have some. If you record with a flat line, you may never make a quality recording through post production patching and corrections. I’m leery about not getting such a warning in Waveform (dB).
Koz