This page allows you to listen to a sample recording (Microsoft Bob from Wikipedia). You can switch between the different codecs and experience the difference in audio quality. Below the table is a spectrum visualization, which shows how higher frequencies are not reproduced by some of the older/lower bitrate codecs.
| Codec | Sample rate | Bandwidth |
|---|
The spectrum visualizer shows the magnitude of an input signal versus frequency. On the left are the low tones, towards the right the higher frequencies.