How do I cancel out identical part of two audio files?

[Felix Lee]

Let's say I have two similar audio files in different format (such as MP3 and AAC) from the same master (CD audio or WAV file) and I want to find some differences of quality between the two files. (to examine their quality change and compression techniques)

I did some research on it and figured out a way that I can overlay the two wave shapes (or spectrogram pattern) and cancel out the identical part so that the leftover can demonstrate the better effectiveness of one of the formats.

Can Wavepad actually do that kind of function? It is the only audio software I found that can open AAC files (Reaper and Audacity can't) so I hope it would contain a function like that, but since I am a newbie on this, I have no idea how to actually overlay the two files and delete identical parts. I also searched the Wavepad wiki but no idea.