Here are three audio examples of the same musical excerpt, each at a different sample rate: 44.1 KHz, 22.05 KHz and 11.025 KHz.
Before you listen, keep in mind what we discussed about the Sample Rate, i.e. that, at a given Sample Rate, the highest frequency you can reproduce is equal to half the sample rate.
So, what we can say about these three files is that the first, sampled at 44.1 KHz, will be able to reproduce frequencies up to 22.05 KHz, half the sample rate. What are the highest frequencies that the other sample rates can reproduce?
Use the above Flash movie to play these three excerpts and note the graphic which shows the frequency response of each. The light blue line represents the 44.1 KHz sample (CD quality); the blue line, the 22.05 KHz excerpt (FM quality); the purple line, the 11.025 KHz recording (AM quality). Also note that, up to the point where the 11.025 KHz excerpt "rolls-off", the frequency response of the three excerpts are practically identical.