It never been so easy before..😀
1. Install pavucontrol (PulseAudio Volume Control) using apt-get or the Ubuntu Software Center.
2. Open PulseAudio Volume Control. It should be in the applications menu under Sound and Video.
3. Open Sound Recorder and start recording. Playing any sound at this point would be helpful, as your level indicator should react once you have finished.
4. Go to the “Recording” tab in the PulseAudio Volume Control window.
5. Make sure that “Applications” is selected in the drop down menu on the “Recording” tab.
6. Choose “Monitor of Internal Audio Analog Atereo” from the “Record Stream from” menu in the Sound Recorder entry of the application list.