If you get the MP3 plug in you can then save a track at different MP3 sampling rates and then show the differnce bween them.

To get the MP3 plug in may be difficult if you are not a bit nerdy but there are details here

I have a Madonna track I use sampled at differet bit rates from 320 down to 8kbs. You can load them all into aduacity and switch between them hearing the same song but at different qualities. I'm sure that some 20second clips are probabaly 'fair use' but don't like the idea of emails from Warner Brothers Lawyers. I'll try and find a Creative Commons track that works. I used Ray of Light as it was particually good for this as the first 20seconds or so were sonically quite simple (harder to tell between the various quality) and then when the vocals kicked in it got more complex and so easier to compare.

As a don't-get-sued version I have used the track Seed of Sin by Heifervescent from their album Further Adventures in Monkeyland simply because it was the first free track I found that has a quiet bit at the start that went into a noisy bit.

http://www.jamendo.com/en/album/92051

WHAT TO DO

1) Open a track into audacity

2) Delete all but the fisrt 50 seconds, just to make life easier

3) Go to EDIT --> PREFERENCES --> FILEFORMAT

4) Change the sample rate to whatever you want [i'd suggest that you go for 3/4 that range between highest and lowest]

5) The FILE --> Export as MP3

6) Give it a filename that includes the sampling rate. I put the sampling rate first in the name so it is easy to see when there are lots of tracks in audacity, see 9) below.

7) Repeat 3) - 6) at different sampling rates

8) You now have a selection of MP3 files

9) You can load them all into audacity at once, start playing and then using the MUTE/SOLO button switchs between them without having to start and stop. It does need a bit of practive but it does work.

If you just want the files to play (i.e. 9) only) then they are here in a handy zip file