Fixing Audio
Refer: http://askubuntu.com/questions/508221/sound-input-device-microphone-not-working
I had a similar problem on 14.04, sound input source was blank in the 'Sound Settings'. I did the following, what did the trick is installing 'Audacity', for more info check the following link
sudo apt-get remove --purge alsa-base pulseaudio
sudo apt-get install alsa-base pulseaudio
sudo apt-get install audacity