For example You can use keepvid.com
1. open choosen video on Youtube
2. copy URL adress of that video and paste it into
www.keepvid.com (URL dialog)
3. push button Download
4. select desired video format - for example flv - low quality
5 save the flv video file onto Your hard drive
Later You can extract audio track from such flv video using free Any Video Converter software and save it as mp3
http://www.any-video-converter.com/p...or_video_free/
The next step You can use Audacity software opening this mp3 file, edit and convert it to wav 8 bit mono