Is there another way to restart the sound system if pulseaudio/ALSA don't work?

I've used pulseaudio -k && sudo alsa force-reload a couple of times, and it worked well. The first part kills pulseaudio, the second reloads ALSA. You don't need to restart pulseaudio, because it auto-restarts.

What I do when my sound doesn't work is

killall pulseaudio

and then I press Alt + F2 and type in pulseaudio. It usually works for me.

Just for completeness, in newer Ubuntus versions that use systemd, I used this and it worked well:

systemctl --user restart pulseaudio