Flash cannot read frequency information from sound. Flash can read a sound's volume, pan, duration, file size, and ID3 tags (for mp3 sounds only).
In order to set up a frequency band animation you use a 3rd party software to analyze this data, generate a Flash compatible data file. Set up ActionScript in your FLA to process the data and import both the sound and the data file into your SWF.
aviarts.com - web development and flash development