Comment 6 for bug 156169

Try the following:

Set the desired default volume with gnome-volume-control and store that state as the default by running:

$ sudo alsactl store

To reset the volume to the default when the user logs out:

Create a shell script named alsa with the following content:

#!/bin/sh
/sbin/alsactl restore
exit 0

Put it in /etc/gdm/PostSession