Vista Home S.P. 2 (I know, I know), Audacity 2.1.3 .exe
Hi, i’m a newbie (which my question probably reveals) but have done pretty well with my first project.
Is there a simple way to reverse the fade in or out effect on a section of audio (after the fact, “Undo” no longer available)?
I’ve seen answers online…use Normalize, Reverse…don’t believe these work?
Appreciate your help 
No ‘simple’ way and no complete way.
It is possible to partly reduce the effect of a fade by applying the “inverse” fade. Note that an “inverse” fade is NOT the same as “reverse”.
A simple example where removing the effect is possible:
If you have a partial fade out from full volume to half volume, then the “inverse” is to fade from full volume to double volume.
Limitations and complications:
If the fade that you want to remove is a “linear” fade (like the Audacity Fade In / Fade Out effects), then the inverse fade is NOT linear.
Example, a linear fade from full volume to silence
Half way along this fade we have dropped from full volume to half volume, so to correct at this point we need to double the volume.
3/4 of the way along we have dropped to 1/4 volume, so at this point we need to increase the level x4
7/8 of the way along we have dropped to 1/8 volume, so at this point we need to increase the level x8
and as we get close to silence, the amount of amplification required increases, until we get to the silence at the end and it is impossible to amplify it enough because in silence there is nothing left to amplify.
Approximating a partial correction:
To partially remove a linear fade out, apply the “Adjustable Fade” effect with settings:
Fade Up
Start / End as: %
Mid-fade Adjust: -100
Start: 100%
End: 750%
Preset: None
http://manual.audacityteam.org/man/adjustable_fade.html
You may then be able to tweak the level to make it a bit more even using the “Envelope” tool: Envelope Tool - Audacity Manual