So in theory, if you compare a VBR file to a fixed bitrate file of the same size, you should be able to hear an improvement in the high frequencies (less swishy-ness to the cymbals on the VBR file).

Our resident MPEG compression expert (John) isn't in today so I can't double check what I've written below - it is all IMHO :)

Surely the number of distinct frequencies is more important than specifically high frequencies? The reason crashing cymbals sound so bad at low bitrates is because they contain lots of different frequencies so the encoder has to throw some of them away. In this case VBR can increase the number of frequencies stored and thus improve the quality.

The worst thing for an MPEG audio encoder to have to encode is white noise because it contains a wide range of frequencies. This is noticeable at low bit rates with applause.



--
Mike Crowe
I may not be speaking on behalf of empeg above :-)