Comment 62 for bug 122560

For some reason, the update turned my speakers off.

To turn yours on:

1. Right click on the speaker icon in the upper-righthand part of the application bar, and select Open Volume Control.
2. Go to Switches, and check the box next to Speakers to turn them on.

I didn't finish the ALSA update by the way (see above posts), and the audio hack is off. My guess is Canonical included a fix in today's update :D.