Last time I had really big problems with sound on my HP laptop (running Ubuntu 12.04 and Intel audio card). It was almost impossible to use skype/hangouts/google chat. After a bit of research I realized that the problem appears because of Pulseaudio crashes. I followed this tutorial, removed Pulse and switched to ALSA. Sound was now working OK, but audio hotkeys were not functioning. Apparently the solution from tutorial did not work. After a bit more of research I replaced commands suggested there with this:
Mute: /usr/bin/amixer sset Master toggle Volume up: /usr/bin/amixer -c 0 sset Master,0 2%+ Volume down: /usr/bin/amixer -c 0 sset Master,0 2%-
Everything works fine now.