Comment 1 for bug 396716

since the switch to pulseaudio and policykit the audio group is obsolete and not used in ubuntu anymore

sound is routed through the in-session pulseaudio server who talks to the system soundserver process via dbus.
access is controlled by policykit, the group defaults are absolutely right here ...

since our imx51 kernel in 9.04 has no audio support enabled at all, pulse does what it is supposed to do if there is no alsa device and points correctly to its builtin /dev/null audio device so processes and applications sitting on top of pulse can still connect to something and dont break.