Michael’s blog is well worth reading, and can be viewed at http://www.mgraves.org/voip/2009/05/wideband-voice-thread-at-broadband-reports/

The Gigaset demo is at http://www.gigaset-sound.com/experience_hdsp.html

In this demo, both the high and low ends now reproduce the real telephone sound.  That familiar “stuffiness” that we get from real-world phones is now restored - the old telephone sound that’s fixed with HD Voice. 

This is how the Gigaset demo has processed “narrowband” sound, but note how much sound there is above 3,000 Hz  - even above 10,000, and also below 150 Hz -- the low frequencies.  Both of these are never found in real telephone systems.  Not even theoretically possible.  I think they got their files mixed up.

This is Gigaset’s demo of their HDSP.  The Gigaset doesn’t actually sound like this (the Gigaset runs the 7kHz G.722 HD Voice codec, not 14kHz as demonstrated on their site), but it is a good demo of “ultra wideband” audio, which you also can get in HD Voice using codecs like the G.722.1 Annex C, the Skype SILK codec, and G.719 (which takes you all the way to 20kHz!)  Some current VoIP phones, like the Polycom SoundStation IP6000 and IP7000 speakerphones, provide ultra wideband sound - even better than what you hear in this short clip.