FLV Extract can extract video and audio streams from FLV files without decompressing or recompressing. (http://www.afterdawn.com/software/video_software/video_tools/flv_extract.cfm)
Save Tube Video is a brand-new software product that:
* Can capture online video and save it to your computer
* Can save video in flv and avi formats
* Allows to have as many downloads as you wish at the same time
* Can be used with most popular Internet browsers such as Mozilla Firefox and Internet Explorer
* Is really easy to install
* Is really easy to use
* Doesn’t require much space
* Doesn’t slow down your browser
* Is absolutely FREE!
http://www.savetubevideo.com/
And then you can use tool, that you get get by following the link
http://www.aoamedia.com/audioextractor.htm