I performed countless blind tests on myself and finally gave up (re-)buying more expensive HD tracks. To save some space, I want to convert some of my 1-3 GB albums to 44.1 or 48/16. For that I want to uncover all the badly done masters and cut off all the information that is only noise. (Backup the original downloads on an external drive and forget about them.)
I guess the best way to do that is to use a spectral analyzer. Then, look at the information that is happening above 22 kHz and try to see whether it's actual audio (should be a downward slope) or noise (non-dynamic and constant peaks).
To some extent, Audacity is sufficient. But it limits the analysis to 109 seconds and I noticed that the beginning often has less reach so I have to search the file for the part with the most amount of data. Also, it does not read DSD.
BTW, I'm on a Mac so unfortunately a foobar2k plugin wouldn't help me.
If I got anything wrong, please let me know. I am willing to learn!