On a brand new Acer Extensa 5230E, I've installed Kubuntu Jaunty 9.04. Everything worked out of the box, including network interface, WLAN - even the Intel HDA audio.
However, I've installed Firefox and Flash and there was no sound - but *only* in Flash/Firefox.
SOLUTION
By default, only the "master" and/or "headphone" output are displayed in the mixer, but not "PCM". Firefox requires the "PCM" volume to be non-zero.
Do the following:
- Either run "alsamixer" from the commandline (=Alt+F2 and then enter "konsole")
...or tell kmix to display PCM, too and turn up the volume in kmix. Here's how:
1) Left-click on the small speaker icon in the KDE panel.
2) Open the mixer (click on the "mixer" button)
3) open the menu entry "settings > configure channels"
4) make sure "PCM" is checked
5) apply and in the mixer turn the PCM volume up