i have some CDs that are brick-walled and want to see if i can decrease listener fatigue using some audacity effects. is there a tutorial to do this? the basic steps seem to de-amplify the wave file then clip-fix it. after that I’ve read that some normalization involving DC-Offset. I have no idea what this is and wondered if it is essential. any help would be much appreciated. i’m a total newbie at this. 
i have some CDs that are brick-walled
Meaning what? They’re amateur music from say a concert recorded on a camcorder and pressed to disk?
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Reduce the volume, yes. All that does is reduce the loudness, but you’ll need to do that to give succeeding tools a place to work.
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Clip Fix corrects one or two overload points per minute by guessing the damaged wave’s original shape based on surrounding work. If the surrounding work is damaged, too, then that’s the end of the show. Clip Fix will not rescue a dense, tight, badly overloaded show, and typically, nobody else will, either.
Normalization is a fancy amplifier and if you didn’t have DC problems with the original work you won’t need to remove the offset.
To get a better idea of the problem, post some of it to the forum.
– Audacity Forum - Posting Files
https://forum.audacityteam.org/t/how-to-attach-files-to-forum-posts/24026/1
Koz
Okay. Makes sense to me now. They are some metal CDs that are just bricked. I had read of declining as a way to make them more listenable. Thanks!
Sounds like you are trying to reverse dynamic range compression.
An “expander” is the opposite of (dynamic range) compressor : it expands the dynamic range : exaggerates the differences in volume.
A popular plugin for Audacity is “Chris’s Compressor” : if you put a negative value for compression in Chris’s compressor it works as an expander.
If the track is extremely compressed (“brick wall”) there are no differences in volume which can be exaggerated by an expander 
. If that is the case you could use Audacity’s envelope tool to apply your own custom variations in volume, (a time consuming task)
https://en.wikipedia.org/wiki/File:Clipping_compared_to_limiting.svg
Nice pictures Trebor.
Would you care to do one in the same style for a “lookahead limiter”?
I think these pictures would be useful on the Audacity wiki.
They are from wikipedia … File:Clipping compared to limiting.svg - Wikipedia