What is bark band or bark frequency in WMA ...?
http://en.wikipedia.org/wiki/Bark_scale (http://en.wikipedia.org/wiki/Bark_scale)
Bark transformation converts a linear frequency scale into bands that correspond better to human hearing and is used in psychoacoustic compression such as MP3, and presumably WMA. Don't use WMA encoder myself, so I'll just give you that pointer. Follow the links at the bottom for more info.