Extract, Separate Audio from Video [Tricks and Free Software].

Here are the free softwares so that you can separate or extract audio from video:
1) VLC Player (Link)

• Open up VLC
• Click on Media Menu
• Click on Convert/Save
• Select the video file
• Click on “Convert/Save”
• Enter the destination folder with a filename containing extension “.mp3″
• In convert window, click on “Edit Selected Profile” button
• Under Encapsulation tab, select “WAV”
• Under “Audio Codec tab”, choose a Bitrate, amount of channels, Sample Rate, and then click the Save button
• Click on Start in convert window
• Once it is finished, you’ll see the converted audio

Check howtogeek guide with screenshots
2) Free Audio Extractor (Link)
Free Audio Extractor allow you to extract/convert entire or parts of your FLV, MP4, AVI, WMV, ASF, MOV, MP3, WMA, M4A, AAC, WAV, MP2 files. Save to Mp3, Wma, Ogg, Flac… try it! it’s easy and it’s free!

3) Free Video to MP3 Converter (Link)
Free Video to MP3 Converter automatically fills the title tag and the artwork, taking a snapshot from the middle of video, which can be seen in iTunes, Winamp or just a Windows Explorer folder.

4) AoA Audio Extractor (Link)
With AoA Audio Extractor, you can easily extract audio tracks from AVI, MPEG, MPG, FLV (Flash Video), DAT, WMV, MOV, MP4, 3GP video files and save them as MP3, WAV and AC3 formats.