How To Rip Audio From Video File?
There are many methods depending upon the video container used. But for general use just using Media Player Classic DSM converter works fairly well.
Open the DSM converter in the File->utils menu.
Right click the window and add file.
then right click the audio and select demux.
use windows movie maker, open the video, delete the video file but not the audio, and extract it as a sound file
Just use MKVToolnix to extract the audio file you want from a .mkv file.