http://sounds.interbug.com/2007/10/28/a-comparison-of-hd-radio-xm-radio-and-am-radio/
The following samples represent the following radio formats:
* HD-AM
- 24 kbps, KFAB, Omaha
* XM low bitrate talk radio
- 24 kbps
* Standard AM
- KFAB, Omaha
Mainly these samples exist to show what digital HD Radio sounds like on AM. Recently the FCC granted radio stations the privilege to broadcast HD-AM at night. This makes a world of difference for talk radio shows.
According to sources on the web, both HD-AM and XM Talk 165 broadcast around 24 kbps. Their audio samples do sound about the same to the ear.
The compression artifacts on both HD AM and XM radio are quite noticeable at this low bitrate. A strong AM signal on a good radio can rival the digital in overall fidelity. However, the lack of hiss, pop and fade, along with immunity from outside interference makes the digital experience more enjoyable.